Smoothing in excimer refractive surgery

Smoothing in excimer refractive surgery

Paolo Vinciguerra and Fabrizio I. Camesasca

Department of Ophthalmology, Istituto Clinico Humanitas, Milano, Italy

The quest for a regular ablated surface

A cornerstone in refractive surgery is the concept that corneal regularity is more important than its transparency. This can easily be clarified by an example: window glass is a transparent media, and raindrops on it are also transparent. However, glass covered with raindrops, even if transparent, does not allow good quality of vision, because of its irregularity. On the other hand, a pair of sunglasses is not a perfectly transparent media, but permits good quality of vision because of its regularity.

Refractive surgery, for the most part in the past, but even nowadays as well, can lead to inconstant results. Anatomo-functional (visual acuity, postoperative refraction, haze), as well as comfort (contrast sensitivity, night halos, glare), problems may be responsible for unreliable results. Several factors can be related to these problems: the patient, the instruments used, the set parameters, the postoperative treatment. Patientrelated causes are mainly connected to the corneal reparative response elicited by excimer ablation. Healing may be more or less intense depending on a patient’s age (the reaction in younger patients is greater), or on the presence of previously undetected systemic diseases (diabetes may hamper re-epithelialization, a tendency to develop hyperplasticscarsmayleadtocornealstromaltissuehyperplasia,etc.).Adequatetearing is another important factor, mandatory for a proper epithelial distribution in a laminar pattern.

Differenttypesofexcimerlaserhaveadifferentinfluenceonthefinalresult,according to their beams and ablation geometry. Each ablation pattern induces moderate surface irregularity, resulting from the overlap of each laser spot. No presently available laser beam, even if regularly positioned in a side-to-side manner, can perfectly fill a surface without leaving small unexposed areas.

Irregularities are in part related to the features of the excimer ablating beam, and in part to intraoperative eye motion. The latter induces the steep margins of a multi-step ablation when concentricity is lost, irregularities due to more or less prolonged loss of fixation, as well as the small irregularities related to saccadic eye motions. The former induces focal irregularities related to lack of beam homogeneity. Broad-beam lasers, using repeated circular ablations with progressively decreasing diameters, induce amphitheater-like ablation with concentric steps. Scanning slit-beam lasers impart pa-

Address for correspondence: Paolo Vinciguerra, MD, Via Ripamonti 205, 20110 Milan, Italy, e-mail: vincieye@tin.it

Wavefront and Emerging Refractive Technologies, pp. 69–86

Proceedings of the 51st Annual Symposium of the New Orleans Academy of Ophthalmology, New Orleans, LA, USA, February 22-24, 2002

edited by Jill B. Koury

© 2003 Kugler Publications, The Hague, The Netherlands

rallel ablations, creating a fenestrated pattern with steps that can be particularly magnified by sudden eye movements. Flying spot lasers act by randomized ablation with a diameter ranging from 0.8-2 mm, and may induce a fine granular, ‘beaten metal’ pattern of irregularities by partial overlapping of small circular spots.

The biological result of this irregularity is an increase in the inflammatory response, with a higher probability of haze and regression.

In LASIK eyes, suboptimal flap overlap leads to changes in the interface, with a worse optical result and an increase in the normal inflammatory response.

Different ablation diameters, as well as the presence and size of transition zones, may also influence the final result. In LASIK, the microkeratome has a relevant role related to such factors as plate stability, speed, and sharpness of the blade, as well as quality, quantity, and stability of suction.

Furthermore, an extremely important factor for successful photoablation is the creation of a regular corneal profile without sharp and steep changes in curvature. These irregular curvature changes may induce an excessive reparative response, with increased deposition of collagen and, eventually, a reduction in the desired refractive effect. It is a well-known fact that treating low grade ametropias leads to more constant results,whileregularcornealprofilesarehardtoattainwhencorrectinghighametropias. This observation leads us to hypothesize the presence of a small error at each ablation that, when repeated a number of times, induces a total relevant amount of error.

Finally, postoperative treatment may influence the course of refraction and haze. Several studies have taken into account all these factors and have verified their possible influence, unfortunately without a completely convincing explanation of the abovementioned unreliability in results. The search for improvement in reliability is presently driving the development and application of custom ablation.

Searchingforpossibleanswers,wedevotedourattentiontothequalityoftheablation surface. Following corneal disepithelialization, the refractive surgeon can observe the regular surface of Bowman’s membrane. This features a continuous, mirror-like surface, without macroor micro-irregularities. Theoretically, a perfect ablation should recreate thisregularsurface,whileinducingadifferentprofileofcurvature.Lossoftransparency, sudden changes in curvature, and surface irregularities, all diffract light rays and decrease the quality of vision.

Evaluation of the ablated surface

Prompted by these observations, we decided to study, both in the immediate postoperative period and intraoperatively, surface qualities that could lead to a better result. Initially, we examined corneal surfaces with a slit lamp, a method that unfortunately only highlights major irregularities.

The use of digitalized retroillumination with the Scheimpflug camera provided us with a better understanding of corneal surface and its properties. The Scheimpflug camera is a photographic system that provides a global analysis of the ablation surface, both superficially and at the stromal interface level. Digitalized retroillumination is attained through illumination of the ocular fundus, and the red reflex is used to examine the cornea, illuminated from inside the eye when dioptric media are transparent. Figure 1 presents a simplified scheme of digitalized retroillumination with the Scheimpflug camera. With this device, we can obtain a representation of the ablated surface that, in a very detailed fashion, highlights not only corneal opacities, but also surface

Fig. 1. Simplified scheme of digitalized retroillumination with a Scheimpflug camera.

irregularities and even intrastromal changes in transparency. All these changes induce lightdiffraction,causedbylightpassingthroughmediawithdifferingrefractionindexes that is deviated from its original linear direction. It is important to point out that light diffraction takes place not only in the presence of opacities, but also when small irregularities of the corneal surface, changes in cornea and lens thickness, sudden curvature changes of the anterior and posterior corneal surface, and lacunae and folds in the LASIK flap interface, are present. The Scheimpflug camera provides information on the quality of light transmission through the ocular media. Evaluation of severity, depth, light absorption, and thus density of corneal surface and stromal opacities and irregularities, featuring different indexes of refraction with respect to normal cornea, can be obtained. Sudden and irregular changes in homogeneity of the refraction index of the cornea reduce the amount of light reaching the retina. The less lighted the corneal image, the less light perceived by the patient. Thus, all the above-mentioned changes worsen the patient’s vision.

When observing a normal cornea with digitalized retroillumination and a dilated pupil, we will see an intensely lighted reflex, indicating good transit of light through the cornea, with no diffraction. On the other hand, when examining a patient immediately after refractive surgery, a fine irregularity is present, with weaker light reflex,indicatingthepresenceofdiffraction.Aweaklightreflexmeanslesslightreaching the retina, with reduced contrast sensitivity.

The Scheimpflug camera can also be applied in LASIK eyes for the evaluation of the flap interface. At this level, diffraction may occur because of incongruities in the two facing surfaces, flap and stromal bed. These changes cannot be seen on topography and seldom on slit-lamp examination.

We used the Nidek NM 100 Scheimpflug camera (Nidek Ltd, Gamagori, Japan) to evaluate corneal surface irregularities after refractive surgery. We have thus been able to classify these irregularities as follows:

a.micro-irregularities: constantly generated during photoablation, due to saccadic eye

Fig. 2. Grade 1, no irregularity. LASIK eye. Note the smooth ablation surface, either regular or with fine granularity, with no visible ablation border or major irregularities.

motions, breathing, cardiac ocular pulse, and laser beam application modalities on the corneal surface, even in the presence of an advanced eye tracking system;

b. macro-irregularities: caused by sudden head or eye motion, incomplete cleaning of the stromal bed, or abnormalities in excimer laser operation, as well as changes in the quality of the laser optical pathway.

Acornealsurfaceirregularityscalemaybeestablishedandevaluatedintraoperatively withtheScheimpflugcamerastraightafterphotoablation,beforecontactlensapplication during photorefractive keratectomy (PRK), epithelium repositioning during LASEK, or flap repositioning during LASIK. We have developed a scale with three different grades of severity:

Grade 1. No irregularity: smooth ablation surface, regular or with fine granularity, with no visible ablation border, mostly concentric steps, no major irregularities (Figs. 2 and 3).

Grade 2. Moderate irregularities: diffused or focal irregularities, ablation borders visible but not sharp, single steps sometimes decentered, no flap interface folds (Figs. 4 and 5).

Grade 3. Severe irregularities: macro-irregularities of ablation, relevant stromal islands inducing light diffraction, sharp ablation borders, decentered steps, severe flap interface folds during LASIK. All these irregularities induce marked light diffraction, and show up in a very dark manner on Scheimpflug images. Therefore, they correspond to areas where the visual quality is markedly reduced (Fig. 6).

Clinical study 1

With a Scheimpflug camera, we examined 80 eyes that had undergone LASEK (n = 40) orLASIK(n=40),anddividedthemintothreegroupsaccordingtotheabove-mentioned scale of irregularity, with Group 1 including eyes with no irregularities, Group 2 those with moderate irregularities, and Group 3 those with severe irregularities. At the end of follow-up, 12 months after surgery, spherical equivalent (SE) refraction was –0.23

Fig. 7. Difference from planned emmetropia at 12 months between the three groups of LASEK eyes. Note how Group 1 eyes have a higher percentage of eyes close to the desired refraction.

Fig. 8. Difference from planned emmetropia at 12 months. Same evaluation as Figure 2, in LASIK eyes.

± 0.48 D in Group 1, -0.78 ± 0.8 D in Group 2, and –1.45 ± 0.92 D in Group 3. Figure 7 shows the difference from the planned emmetropia among the three groups in LASEK eyes, and Figure 8 in LASIK eyes. Figure 9 reports the lower frequency of relevant haze observed in Group 1 LASEK eyes. Finally, Figure 10 presents the gained and lost lines of best-corrected visual acuity at 12 months, in all cases. Group 1, including eyes with no corneal irregularity, always fared better than the other two groups.

Fig. 14. Postoperative topography of a LASEK eye treated with a small ablation zone and no smoothing. The high dioptric gradient, indicated by the visible, thick red ring, shows how the anatomical continuity between treated and untreated corneas is profoundly altered.

treatment. Its target is to achieve a regular ablated surface (Grade 1 of the abovementioned scale). Severe irregularities are thus eliminated, if possible, and moderate irregularities reduced. Furthermore, ablation margins are smoothed, improving the anatomical connection between ablated and normal cornea (Figs. 14 and 15). This latter feature is decisive in PRK and LASEK for reducing the stimulus toward excessive scarring tissue deposition with consequent regression, and in LASIK for providing an interfacewithout lacunaeorfolds.Reducing the high dioptricgradient(Fig. 14),a source of optical aberrations such as spherical aberration, improves the optical performance of the final corneal surface.

Masking fluid

Smoothing requires an appropriate masking fluid,2 with the following properties:

•an ablation rate similar to the corneal rate. Ablation rate indicates the amount of material ablated at each laser pass. If the masking fluid has an ablation rate greater than that of the corneal stroma, stromal irregularities will be maintained, while a lower ablation rate will lead to the undesired removal of parts of the stroma;

•superficial tension equal to that of the corneal epithelium;

Fig. 15. Postoperative topography of a LASEK eye treated with a wide ablation zone and smoothing. The dioptric gradient is contained, the topography is almost monochromatic, and the anatomical continuity between treated and untreated corneas is preserved.

•transparency;

•high bio-adhesiveness, low viscosity, to be distributed in a thin regular film over the stromal bed;

•a shear rate similar to that of a viscoelastic substance; this to allow lamination with a thickness related to the speed of the spatula passes, as described below;

•non-Newtonian behavior with enough elasticity to permit better absorption of the laser beam shock wave;

•sterility with no impurities;

•high UV absorption.

Masking fluids commonly used in refractive surgery contain hyaluronic acid. Of these, we prefer those with short chains and a low molecular weight.

Surgical technique

The patient is informed about all the operative steps of surgical technique, as well as about the duration of treatment. A strong lid speculum, such as the Castroviejo type

used in retinal surgery, should be used to achieve a wide surgical field, proper cornea exposure, and to allow for the rapid outflow of the fluids used intraoperatively without the formation of pools.

After LASEK, and before starting the smoothing process, it is recommended that the operative field be carefully washed with cooled BSS in order to eliminate all residues generated during ablation, as well as any surfactant.

Excessive corneal heating can induce stromal collagen chain changes. In order to limit corneal heating during smoothing, it is important to cool the cornea with chilled BSS or BSS ice cubes. Vinciguerra and Prussiani4 have developed special metallic cylinders that can be chilled separately and that limit tissue hydration, and which are thus particularly useful for smoothing after LASIK.

After these preparatory maneuvers, smoothing is started with one to two drops of masking fluid on the center of the cornea. We use the Vinciguerra solution (hyaluronic acid 0.4%, Laservis, Chemedica, Munich), which has the same ablation rate as a normal cornea and allows a regular ablation rate.1-3 Masking fluid is carefully distributed by means of a special spatula (Buratto’s spatula, ASICO, CA). When a dry area appears, fluid is added and continuously redistributed with the special spatula. Never ablate on a dry surface. Adequate manual experience in continuous fluid redistribution, in order to ensure that major irregularities emerge and are ablated, will come with practice. Fluid lamination can be performed by means of two methods: a fast, to-and-fro motion on the stromal surface permits homogeneous lamination of the masking fluid; conversely, slow and unidirectional motion with final lifting of the spatula, will induce thinning of the fluid. In the first phase of smoothing, when large irregularities may be present, lamination must be thin, in order to allow the irregularity ‘peaks’ to emerge and be selectively ablated, while protecting the lower corneal areas (‘valleys’). The surface will improve rapidly, as can be highlighted by intraoperative keratoscopy (Fig. 16).

In the ensuing phases, when only small residual irregularities still remain, the masking fluid will follow their profile, without highlighting peaks and valleys. It would now be useful to perform lamination while keeping the fluid thicker in order to cover the entire stromal surface homogeneously. With a fluid that is thicker in valleys and thinner on residual peaks, ablation through the masking fluid will mostly be performed on the peaks. In fact, it must be remembered that the excimer laser ablates even through the masking fluid. Precise determination of the best frequency of lamination can be achieved using fluorescein, which shows dry areas promptly and by listening carefully to the changes in acoustic features of the corneal ablation process. Dry areas, often visible as umbilicate points on the surface of the masking fluid, disappear during smoothing, thereby proving their nature as irregularities emerging from the masking fluid.

A neutral, PTK-style ablation is performed, with a diameter of at least 9 mm, in order to avoid hyperopic shift. A low frequency ablation rate (i.e., 10 Hz) is used in order to avoid corneal heating, as well as to prevent endothelial damage and postoperative stromal inflammation. The laser is set at a maximum of 30 m ablation, in order to obtain 8 m of real ablation.

Smoothing in LASIK

When LASIK has been performed, generous preliminary washout of the operative field iscontraindicated,sincethiscaninduceflaphingeedemaandhamperflaprepositioning.

Fig. 16. Grade 2 irregularities, flying spot laser. From right to left: progressive improvement of the surface during smoothing.

A delicate factor during smoothing in LASIK eyes is the flap hinge, which hampers the constant outflow of the excess of masking fluid. This excess must be constantly removed with Merocel sponges in order to prevent a fluid meniscus, which could induce relevant refractive defects (astigmatism and hyperopia). During treatment, the flap must be adequately hydrated, otherwise repositioning may be troublesome. Flap repositioning must be accurate, if necessary stretching it into smooth folds or striae. The margins of the flap and of the stromal bed must be preserved in order to prevent epithelial ingrowth. In the case of previous flap folds that cannot be regularized, flap suturing may be indicated. A small flap (7.5-8.0 mm) may compel ablation on a very small portion of the cornea, with consequent tissue removal in a limited portion of the stroma, a situation of localized flattening inducing hyperopia. Therefore, in this case, the risk of inducing hyperopia must be clearly explained to the patient.4

PTK after LASIK is a procedure that must be limited in duration. Tissue hydration, induced by the use of fluid, may become excessive and can hamper precise flap repositioning. Flap irregularities should not be treated by PTK: they must be identified and the patient must be informed preoperatively of the consequent limits in the results of treatment.

Considering all the above-mentioned facts, smoothing after LASIK is a procedure that should only be approached after adequate experience of smoothing in easier cases, such as in post-LASEK eyes.

Common questions about smoothing

Does smoothing influence final refraction? If properly performed, the ablation induced by smoothing does not hamper the final refractive result. The ablation diameter is impor-

tant; when it is less than 8-9 mm, it may induce hyperopia. An 8- m ablation on 8-9 mm maintains corneal curvature values, without modifying the initial refraction.

Is the ablation frequency decisive? We use a 10 Hz ablation frequency, since corneal heating can be induced by higher frequencies. However, corneal cooling before and after smoothing is always recommended.

Can smoothing can be performed with a flying spot laser? Yes, but in this case, the surgeon must verify that PTK-style ablation has a definitively neutral ablation profile, with no refractive effect.

If smoothing is so important, why it is not used more commonly? Common doubts about smoothing include its reputation as a complex, refractively unpredictable, or useless technique. If the technique described above is followed, smoothing is not a difficult technique. It is important to set the laser appropriately, approach the technique with caution, and undertake some intraoperative controls in the first cases (see Appendix), in order to verify that smoothing does not affect the corneal situation negatively.

Can smoothing help in retreatments? When the surgeon has acquired the smoothing technique, this adds to the tools that can be used in retreatments, particularly when intraoperative control techniques have been mastered. Corneal irregularity is one of themostimportantfactorsintheunpredictabilityofresultsassociatedwithretreatments. Intraoperative topography is a mandatory examination for monitoring treatment and progression toward desired goals. In LASIK patients, this examination must be performed directly on the stromal bed, after the flap has been lifted, thus only with instruments that can be used intraoperatively, such as the C.S.O. (C.S.O., Florence) or the Keratron Scout (Optikon 2000, Rome), in which the parts close to the ocular surface can be sterilized.

Contrary to smoothing after PRK, in LASIK, it is important to remember that, when the flap is lifted, a topographical increase in curvature where the flap stromal bed meets the untreated cornea will always be present, indicating the cut margin on the stromal bed. Obviously, this curvature irregularity must not be treated, since it is essential for the correct repositioning of the flap and prevention of epithelial ingrowth.4

References

1.Vinciguerra P, Cro M, Giuffrida S, Airaghi P, De Molfetta V: A new strategy in excimer laser PTK: use of hyaluronic acid solution as masking fluid. Invest Ophthalmol Vis Sci: Poster, Annual Meeting Sarasota, FL, May 1-6, 1994

2.Kornhehl EW, Steinert RF, Puliafito CA: A comparative study of masking fluids for excimer laser phototherapeutic keratectomy. Arch Ophthalmol 109:860-863, 1991

3.Fasano AP, Moreira M, McDonnell PJ, Sinbawy A: Excimer laser smoothing of a reproducible model of anterior corneal surface irregularity. Ophthalmology 98:1782-1785, 1991

4.Vinciguerra P, Prussiani A: Fotocheratectomia terapeutica (PTK). In: Chirurgia Refrattiva: Principi e Tecniche, pp 439-462. Asti: Fabiano 2000

Appendix

Preand intraoperative instrumental diagnostics

This appendix illustrates how to perform, when needed, various intraoperative controls of the corneal surface and thickness. Since they are mostly used during PTK, this technique has been addressed in the text, even when the same principles are valid for smoothing.

Keratoscopy

Thankstotheprojectionoflightringsontothecorneaandthestudyoftheirmorphology, this examination permits precise evaluation of the shape and regularity of the corneal surface. It is the mainstay of the PTK strategy and pre-, intra-, and postoperative evaluations. Together with pachymetry, it provides information on the progress of PTK surgery, and guides the surgeon in deciding when the planned surgical goal has been achieved. Since it is a dynamic examination, it is mandatory to perform it preoperatively in the presence of a regular tear film. Therefore, the surgeon must ask the patient to blink several times, and acquire the image without tear pools, surface irregularities, or irregular tear distribution. Intraoperatively, when the flap is lifted, the surgeon must lightly wet and evenly distribute the fluid on the stromal bed.

Several features of the keratoscopic rings must be considered. For the sake of completeness, the descriptions of these features will refer to keratoscopy performed on the corneal surface before flap lifting:

•Shaperegularity.Keratoscopic ringsthatare regularinshape indicateacorneal surface with good optical features and regular lamination of the tear fluid. The rings are well delineated, with no deformations, interruptions, or irregularities. There is clear contrast between light and dark rings.

•Continuity. Regular continuous rings are typical of regular corneal surface and tear film distribution. Interruptions indicate irregular corneal areas with poor optical quality (i.e., leukomas), as well as the presence of secretion or breaks in the tear film. Blinking enables differentiation between surfactant that may be removed and corneal irregularities that will persist.

•Circularity. Regular circular and concentric rings are present when the surface is spherical. In the case of astigmatism, the rings will appear oval-shaped along the axis of greatest curvature. Elliptical or pear-shaped rings are present in the case of regular or irregular astigmatism, asymmetric astigmatism, with a small or large bow tie.

•Symmetry. Symmetry is typical of the homogeneous distribution of dioptrical power in the various sectors. Asymmetry indicates an important difference in dioptrical power in the various sectors, i.e., in irregular astigmatism.

•Deformations. These may be observed in the presence of irregular astigmatism, which cannot be corrected with a lens, and often induce marked reduction in visual acuity.

•Edges. These are interruptions in the regular circular shape of the keratoscopic ring and can be seen in the case of a full-thickness corneal structure interruption (i.e., perforating wounds or radial keratotomy).

•Inter-ring distance. Lesser or greater distances between rings indicate greater or lesser curvature, respectively. Flat areas display spaced-out rings, curved areas close rings. When the distance is homogeneous, the dioptrical power is evenly distributed.

On the other hand, relevant variations in distance between rings indicate irregular surface dioptrical power.

•Width. This highlights the focal dioptrical power. A thinner ring indicates a steeper area, a wider ring a flatter area.

•Absence. Rings are absent in the case of marked surface anatomical changes, large epithelial defects, or relevant changes in the tear film.

•Focus. When nearby areas are on planes markedly distant from one another, focusing ofringsisnothomogeneous.Itindicatesamarkedsurfaceanomaly,andcannormally be seen in transplants, since graft and recipient areas lie on different planes.

•Centering. If rings appear off center, the patient was probably not staring at the target light properly.

When keratoscopic rings appear to be irregular, off center, or jagged, PTK may eliminate these irregularities, thus improving visual acuity. Conversely, when keratoscopy shows well-centered, round, and regular rings, there is no indication for PTK. When keratoscopyisregular,othercausesofreductioninvisionmustbecarefullyinvestigated. A patient with 20/30 vision and irregular, jagged, and asymmetrical rings will probably see more and with better quality after PTK.

Topography

Derived from processing keratoscopy, topography guides the surgeon in his preoperative evaluation of a PTK patient. Topography offers great accuracy in determining the axis and power of astigmatism, thereby allowing precise determination of visual acuity, and a more accurate prognosis.

The commonly used algorithms are: axial, tangential, altitudinal, pachymetric, and wavefront with the Zernike polynomials analysis. The latter two provide different information, and both are necessary and important in the preoperative evaluation:

•Axial. This scale closely represents the refractive situation on the corneal surface. The dioptrical value of each point is calculated according to an algorithm that accounts for the distance of the point from an axis positioned at the center of the cornea. Using this scale, corneal topography is built up from the center (visual axis) to the periphery, and represents the visual situation of the patient. However, it must be remembered that the dioptrical power of astigmatism is underestimated on this scale.

•Tangential. According to the algorithm of this scale, each point of the corneal surface is calculated by creating a circle tangential to that point. The reference axis connects thepointtothecenterofthecircle,andisthereforedifferentforeachpointconsidered. Thus, a morphological representation of the cornea is generated.

Neither of these two scales represents the actual morphology of the cornea, even though both provide a reliable interpretation. For this reason, several other algorithms and scales have been developed:

•Altimetric. The altimetric map is defined by subtracting the values of the cornea that is being examined from an ideal reference sphere. In this way, differences are defined in altimetric position, above (steeper) or below (flatter) the surface of the ideal sphere.

•Gaussian. This algorithm considers several different parameters, thus providing an evaluation that can be considered intermediate between the tangential and altimetric algorithms, and therefore closer to the actual corneal shape.

•Pachymetric. This map can be obtained with the OrbScan topographer (Bausch and

Lomb, St Louis, MO). Using light scanning of the anterior and posterior corneal surfaces, this instrument undertakes a topographic examination of both surfaces, with axial or tangential algorithms. It also provides a pachymetric map, with details of the stromal thickness at each analyzed point. These three different maps are presented simultaneously, allowing the possible coincidence between topographical and pachymetric irregularities to be estimated.

•Aberrometry. Aberrometric evaluation of the anterior corneal surface simultaneously presents the position and amount of the different sources of aberration. With the Seidel calculation, areas where the wavefront is altered are highlighted, providing an indication of the corneal areas that require regularization with PTK.

Sometimes, altered keratoscopic rings induce an omission in the topographical analysis of the area involved, causing incomplete or erroneous topographical calculations, with falseflatorsteep cornealareas.Topographers suchasthe C.S.O.(Florence)andKeratron Scout (Optikon 2000, Rome) enable manual identification and correction of each ring course, and provide complete and detailed topography. These two topographers are either portable or can be applied to a movable arm and can therefore be used intraoperatively.

Pachymetry

Based on ultrasound, pachymetry determines corneal thickness. It is recommended that it should be considered in relation to the irregularity that is being treated. When stromal irregularities are limited, it is possible to smooth even very thin corneas. When defects are very severe (i.e., inducing 20 D of astigmatism), treatment is not possible even in the case of almost normal corneal thickness.

Round Table

While we wait for wavefront technology, how can we help our unhappy postoperative refractive patients?

Karl G. Stonecipher, MD, moderator

Dr Stonecipher: We always seem to find these kinds of questions that are beating us on the head, and we are always telling our patients about what is next. We have done it forever C just wait, this is coming, we have this new thing, it’s coming. Next year, we’re hoping the FDA will approve this, and we will have this technology available for you, but still you have that patient sitting in the chair and you are trying to figure out what to do now. It can be very challenging. I’d like to go backwards for a moment and say that a lot of the problems I see referred to me, and I don’t know what the panel will say, are postoperative LASIK patients who should probably have never been operated on in the first place.

This is a patient who has a form fruste keratoconus (Fig. 1), but you also have a lot of dry spots and I am putting it up there for those as well. She’s a subclinical forme fruste

Fig. 1. Don’t operate in the first place!

Wavefront and Emerging Refractive Technologies, pp. 87–95

Proceedings of the 51st Annual Symposium of the New Orleans Academy of Ophthalmology, New Orleans, LA, USA, February 22-24, 2002

edited by Jill B. Koury

© 2003 Kugler Publications, The Hague, The Netherlands

keratonus patient and we now have software on our Humphrey analyzers for revealing patients such as this. It may be too sensitive, it may not be sensitive enough in certain instances, but the point is that recognizing some of these issues before you operate on the patient is very important. If you ask me the number one complication I see, it is some sort of form fruste corneal dystrophy that probably should have been addressed initially. And Dr Durrie alluded to this earlier in terms of these corneal topographical asymmetric bow-ties. What do we do with these people, do we operate on them now or not, or do we wait? I’d like you to comment, Dan, a bit more on that in terms of if you have a patient who comes in with what you say is not classical disease, what are you going to do, what are you going to tell that patient in terms of your asymmetric bow-ties?

Daniel S. Durrie, MD: I don’t operate on them, and the reason for this is because in the past I have, and these are the patients who come back and you are essentially talking about a cornea that is on tilt or the lower part of the cornea is steeper, and then we’re focusing right in the center with a symmetrical treatment, and you are essentially operating on the side of a hill. You magnify the problem. It is also interesting that, I’ve gone back and everyone else can put their two-cents’ worth on this one too, people who are sent to me for ectasia, if I can get the preoperative topography, always have evidence of a corneal topographical abnormality. People who are thinking that they are inducing keratoconus, it is basically something that was there preoperatively and they just missed it. I am constantly seeing those. So, I really agree that if you have an asymmetric bow-tie or, on an OrbScan, you have a yellow spot that is not in the center, I don’t think you should operate on those people now, because I think we have better technology for them coming along.

Dr Stonecipher: I want to extend this a little more and say that what we learned in the old days with RK was that we thought, “Oh great, there’s a B10.00 or 11.00, we can help them with this and at least get their glasses thinner, and then what you see now is that we’re doing the reverse. Whenever I start a new clinical trial, I am operating on the B1.00s and B2.00s first or the +1.00s and +2.00s first because a 10% error in a B1.00 is a tenth of a diopter; it’s a full diopter in a B10.00. So I think we’re going backwards. And Steve Schallhorn will say the first patients they did with the VisX laser were the easy ones, the no-brainers, and I think that is where we’re headed with some of this stuff.

Ron,Iwillgiveyouthisone.Whatistheroleofpharmacologicalpupilsizemodification? Do you like pilocarpine, do you like Alphagan, what are you doing these days when people come in with halos beating your door down, and what are you suggesting for them?

Ronald R. Krueger, MD, MSE: They don’t always come in with halos, per se, they come in with some blurry vision. And really, it is night-time driving dysfunction in some way in most cases. If it’s daytime and night-time, it’s probably not going to make much of a difference if you try to do something pharmacologically. In the beginning, I did try to use diluted pilocarpine in some cases when they look like they were really struggling, but that’s tough because you get brow ache with it, and things along those lines. I find that sometimes Alphagan does seem to help a bit.

Fig. 2. Confoscan. Clinical applications in refractive surgery.

Dr Stonecipher: One thing is that at least it gives the patient something to do; at least you are trying to do something for them.

Stephen G. Slade, MD, FACS: I have used Alphagan on about three patients like that and I am pretty optimistic about it. Also, in patients who come back complaining of night vision problems, maybe what Ron was alluding to, be real careful and make sure they don’t have residual cylinder that you’re not picking up. Sometimes you can go back and re-treat them and fix that problem; it’s actually a refractive problem, not necessarily related to their pupil.

Dr Stonecipher: I agree with that. In some instances regarding night-time, driving glasses may even help in that you may have a residual refractive error and you may not have enough room to do any more, but even if you just give them glasses and Alphagan, it really seems to make a big difference.

Dr Krueger: If you give a patient monovision and they are happy with their monovision, but they are struggling at night and they can’t drive well enough, just give them nighttime glasses to correct both eyes for distance.

Steven Schallhorn, MD: The other thing I have tried in young patients is over-minusing them a little for night-driving glasses, night myopia. This does a couple of things, and it can induce a little accommodation which they can easily handle, like B0.50, and it also constricts their pupil. I occasionally find this useful too.

Dr Stonecipher: Before I get too far off on who not to operate on, one of the neat things you are seeing now is these confoscans (Fig. 2) and confocals, and we have had them around for ten, eleven, or twelve years now, but we are finding more and more applications. I am not a paid consultant; I don’t have any interest in this product, but I do know that we are able to look at different layers of the cornea. One of the things I am doing now in these form fruste suspects is getting confocal microscopy on them.

What you can find in early keratoconus patients are what are classically late keratoconus Vogt’s striae, we are picking them up early, so many of the patients who just don’t seem quite right, and you are looking at the OrbScan or they have normal pachymetry when they come in, and now clinically we are seeing these fine little striae by confocal microscopy and making the correct diagnosis. You are going to be seeing more and more of these. The company is now starting to sell more of them and I think it is going to be a tool that we will be able to use pretty soon as well.

Steve Schallhorn, tell us about CAP. Where is CAP, and are we using custom ablation profiles with VisX or not?

Dr Schallhorn: CAP was recently approved. It is a way of doing a customized ablation where you can modify the diameter and the power of the correction and also the XY direction, where you want to put it on the cornea. It really allows flexibility for treating things like central islands. This is what it was really more geared up for. As far as its application goes, I’m kind of at a crossroads at this point with therapeutic wavefrontguided ablations perhaps around the corner. By around the corner I mean in the next year or two. They are certainly doing clinical trials now, but whether that would be a better option than a CAP... But I think CAP is available now, and the primary benefit would probably be an isolated central island that you would want to treat now and that perhaps can’t wait.

Dr Slade: Wasn’t the actual approval for decentrations? The CAP? We did about 200 topographically based ablations for various things, and the decentrations worked out pretty well. These were computer-guided where it would actually generate a treatment based on the topography with the CAP technique. I think it’s a real plus for that laser, but it is still guided by the surgeon. It just allows you to pick an ellipse or a sphere, and then pick where you want to put it and pick the depth and diameter of that ellipse or sphere. But it is probably the best thing right now B it’s the only thing right now that is approved to be done.

Dr Schallhorn: It is the only thing approved right now, but the real thought is if you have a patient who needs something like that who has an aberration, whether or not you would want to do CAP or wait for a therapeutic wavefront-guided, which could perhaps do a much better job of guiding a treatment, that’s really up in the air right now.

Dr Stonecipher: I’m part of the BioMask treatment trials, which Ioannis alluded to, and I’d like Ioannis and Paola to comment because they have access to the technology. Our problem with BioMask was that, unfortunately, many times BioMask stuck to the contact lens much better than it did to the cornea. So Ioannis has figured out ways of trying to prevent that, and he showed you that just now. But, could you guys comment on, if you have a central island, if you have a decentration, and you don’t think the patient is appropriate for a wavefront (I’m going to talk about that in just a little bit), who you are treating with BioMask, on whom you are trying other things like CAP technology, or something of that nature? Ioannis or Paolo?

Ioannis G. Pallikaris, MD: Except for the Palm or smoothing approach with regard to the eccentric ablation profile problem, I am now using more and more... it depends on

the refraction of the patient. If I have a hyperopic case or a myopic case, it’s different, but if it is a hyperopic case, I am using the radiofrequency more and more in the way that I am also using a relaxing incision. It’s the same principle. Either you can use relaxing incisions or radiofrequencies, or you can also use ICR. So, in some cases, I use ICR to decenter the ablation and it works very nicely. Everything depends on how the refraction was before. Again, if this case has a lot of striae, for example, you want to treat the central cornea, you are going to use the expanding peripheral keratoplasty style procedures much more often. If it is very small, you will probably use an ICR or relaxing incision, but it is the only way I try to treat very eccentric cases, by the way.

Dr Stonecipher: Dan, can you expand on where we are with Intacs? I know Brian S. Boxer Wachler is doing a lot of neat things with ectasia and keratoconus with the Intacs. For those of us who have ectasia, and we are trying to figure out what to do with their ectatic patient cornea, is the Intacs an answer right now?

Dr Durrie: I have done about 20 patients who either have keratoconus or some kind of inferior asymmetry, and I have done them by just putting an Intacs above, I’ve put them in both above and below, and in varied sizes. And I think that all it does is kind of stretch it and lower the bump. It doesn’t really cure the asymmetry, it just stretches it this way. The data that Joseph Calin have shown and Brian Boxer Wachler is looking at, is if you have a keratoconus patient who is heading toward a transplant, you can stabilize them and sometimes improve their best-corrected spectacle vision. In a lot of the patients we’re talking about, that is not what they are looking for at all. If you do an Intacs on someone, you had better make sure that it is the right patient, because if they are thinking that they are going to be 20/20 and perfect and you are thinking that you are just going to stabilize their keratoconus, you have to get your things aligned. I just looked at Joseph Calin’s three-year data now and these matched his one-year data, so that is as long as we have, that first done three years ago. So we really don’t know. I think that the clinical study being done on this, people pooling their data, is very important because adding some tissue to the cornea would be kind of nice in some cases. The other thing I have been thinking about is that I have worked with Dr Mendez with the CK, the Refractec device down in Mexico, and he uses it to shrink the cornea down below, which I am interested in, because if you have patients who have a high spot down below, maybe putting in a couple of radiofrequency spots outside that to pull it down might work just as well as trying to pick it up on the superior area. Once this is an approved device, we can do some off-label treatments in these patients and see what happens.

Dr Stonecipher: I don’t know if any of you have had the opportunity to work with the contact lenses. Dr Phil Busremi, who is in Greensboro, has access to a lot of the Italian contact lenses, and Paolo knows that well. We’re using non-wavefront made contact lenses and Saturn style lenses with soft skirts and hard centers, and are seeing success in some of these patients who aren’t seeing what they want. Paolo, could you comment on special wavefront-based contact lenses? The question is basically, for the unhappy LASIK patient, can we make a contact lens today using their wavefront map to help them see better?

Paolo Vinciguerra MD: I don’t have the experience.

Dr Stonecipher: Does anyone on the panel have any experience with wavefront-guided contact lenses?

Panel: No.

Dr Vinciguerra: Do we really need wavefront contact lenses?

Dr Stonecipher: I don’t know. I’m just saying that maybe it’s a bandage until we get the approval. Marguerite?

Marguerite McDonald, MD: There are two companies pursuing this option. Polyvue TechnologiesofCaliforniaisjuststartingaclinicaltrialwheretheywillputthewavefront corrective pattern on a soft lens. They are just about to start this and their laboratory experiments look good, but they haven’t started yet. There is another company making radially asymmetric soft and hard lenses. Right now they have hard, within a week or two they will have soft. The Scout system is what it is called. So basically, a hand-held topographer is used to snap a picture and that is sent to a laboratory and a custom lens is generated. They can do symmetrical or radially asymmetrical lenses. And about 150 optometrists in the USA have this system right now. Ophthalmology is just starting to get into it. In almost every community, there is someone who has the system, and these have a high success rate.

Dr Stonecipher: That is exactly what Phil is using. We’re taking topography pictures and sending them to the company and they make a lens. A lot of these guys came into the picture saying, “I want to get rid of my contact lenses and glasses”, but at least, if they can get them back to point one and seeing again, that will sometimes help with who Steve alluded to, the angry patient.

Laser treatment of irregular astigmatism

Karl G. Stonecipher, MD, moderator

I brought Marc Michelson up here to the table as well because there are several techniques out there, good and bad, but Gilles Lafond has talked about this laser treatment of irregular astigmatism, and basically, the patient comes in, they are referred, they have monocular diplopia. Do we do wavefront? What do we do with these people?

What is your answer to this patient?

•Sorry, but there is nothing to do.

•Wait, it will get better with time.

•Too bad for you, you should have consulted me the first time. I am the only good LASIK surgeon in the country.

•I can suggest a good lawyer.

•You can pray, miracles still occur nowadays.

•In the near future, wavefront technology will be available to correct your problem.

•Retreatment is possible to improve your vision.

I have used Gilles’ technique, and I am not going to steal his thunder, but basically what you try to do is to map out a game plan. I am going to let Marc Michelson talk a little bit about the way in which he maps out these game plans to where you try to do a surgeon-guided customized ablation. I wouldn’t say that, in my hands, it has been the panacea, but I have had a lot of patients who were extremely unhappy turn into 50 or 60% happier and made what they considered late-night problems, functional problems in terms of driving and they work third shift, or something like that, at least got them back to square one where they were more comfortable. Mark, what are your comments?

Marc Michelson, MD: I guess one of the reasons I can do this is because I have the technology to do it, it’s the old Summit Apex Plus laser. It is sort of a back-up laser system and I am going to give the talk tomorrow morning. I started thinking about this about two years ago, and I decided to use a PTK modality and narrow the beam size down to a 2-mm spot size, and to do a random spotted ablation in areas that I thought were topographically related to the abnormalities. What is interesting in the patients I’ve seen who come in with specific refractive errors where they may have a specific axis of cylinder that refractively doesn’t totally correspond to anything that you see topographically, is that it’s obvious that you cannot treat these patients based on the refractive data. You have to look at something beyond that. I have done selected treatments in the high spots, so to speak, and fortunately have been very successful in the small number of patients I am going to report on tomorrow. They have been a mixture of central islands, irregular astigmatisms, non-homogenous ablations is the best way I can place it because they are certainly not decentered ablations, and certainly incongruous refractions to topography. None of the patients we treated lost lines of vision. We have had significant improvements mainly in symptomatology and in eliminating the ghosts, the night vision disturbances, and things like that. I caution you, this is only a selective number of patients, what I would call my collection of severe visual dysfunction patients who have been improved. It is basically a limited application of PTK in selected areas randomly applied to the high spots, in a brief synopsis of how the technique is used.

Dr Stonecipher: Paolo, they want to know what your pearls are for treating unhappy patients: is it always to re-treat them, and what happens when you don’t have a wavefront machine? What are you using other than wavefront to help you make some of these diagnoses?

Dr Vinciguerra: I have intraoperative topography in cases like this. Basically, it is relatively easy to treat them by focal treatment, try without masking fluids, try to normalize this. This is a patient who was treated for B16.00 (Fig. 3).

This is the instantaneous map before and after the re-treatment (Fig. 4), the keratoscopic view is more impressive. You see here before, this is intraoperatively, the change. So you can see that what we basically did in this case is to use the mask that we developed together with Midsolar. With seven masks, you can progressively expose the opposite side and then you can re-center and we remove a few microns here, so that, by the calculation, you remove one-third of the original ablation, so it’s not very

much. Here is another example. I think that in most of these cases that, with a few microns of additional ablation, you can solve everything. Because when you do the calculation in the elevation map, it is not very much... it is like a spherical aberration. Usually the red ring that is showing the spherical aberration is basically 10 µm, not very much. So it is easy to solve this and raise the optical zone size.

Dr Stonecipher: I have a couple more questions that we are going to answer here in just a second. Ron Krueger has a couple of patients who we don’t really have examples of, but I’d at least like to tell you how, with his wavefront machine, he is perhaps able to make some changes that we could apply now.

Dr Krueger: Actually, I mentioned this to Karl earlier, and it is just one particular patient I had who had some complications requiring a secondary flap to be made, at which point there were some splices of tissue there. This is always very difficult when you have an interruption of the first pass when you do a second pass. With some subsequent laser treatments we got his vision much better, but he still had some distortion, some double vision, some glare, that he wasn’t really completely happy about. We measured some coma on his wavefront that happened to be along an axis of a very small amount of astigmatism, something of the order of three-quarters of a diopter of cylinder, or so, and he had coma along one particular orientation. So, I decided to do a one-incision AK along that area, and he came back afterwards and said his symptoms had decreased by at least 50% and he was much happier just from that one-incision AK. So it is kind of interesting, if you start thinking about looking at aberrations and figuring out creative ways of trying to correct some of those subtle aberrations, maybe an asymmetric AK pattern could correct coma with a little cylinder at the same time.

Dr Stonecipher: Who on the panel who has had refractive surgery? We know Dan has. But how many people in the audience have had some type of RK, LASIK, PRK, just raiseyourhands.IknowDickLindstromhassuggestedthatthepenetranceforrefractive surgery is extremely high among ophthalmologists and optometrists; I don’t know about the panel, but I have operated on masses of physicians in the field of eyes. I don’t know about outside the country. Do you guys operate on a lot?

Dr Vinciguerra: Yes, I operate on many ophthalmologists in my country.

Round Table

LASIK complications: new approaches

Steven Schallhorn, MD, moderator

DrSchallhorn:IthoughtIwouldgooversomecommonandmaybesomenot-so-common complications from LASIK and query the panel as to their current treatment modality. As Karl mentioned, these are often best avoided. But sometimes they can’t be avoided, and here is the first example. Despite your best efforts at trying to determine preoperatively if the patient has loose epithelium, basement membrane dystrophy, you end up with a large epithelial defect afterwards. I find that to be an extremely frustrating problem. I’d like to hear from the panel regarding management of large epithelial defects after the microkeratome pass.

Karl G. Stonecipher, MD: I’m almost mimicking Dan’s numbers exactly. He presented thisattheAutonomousUsersMeetingawhilebackintermsofgradinglooseepithelium, and about one in every 350 eyes (and I don’t know, Dan, if your numbers have changed since I last saw that), the grade 4 where it just falls off and they have no basement membrane. They can be young, they can be old. I did a study a while back and looked at the use of Muro 128 in these patients to try to help. I think it does, and I have the data to prove that. So in my 50 and above population for the week before surgery, I have been putting them on Muro 128. It didn’t make a huge difference. It reduced my incidence by about 10-15%, but still that is 10-15% fewer headaches associated with them.

Ronald R. Krueger, MD, MSE: How long do you do that?

Dr Stonecipher: For a week four times a day. I had one on Thursday. The guy was 29 years old, healthy, and I did his first eye and the epithelium was just gone. And you just kind of sit there like you’ve just wrecked your car and you say to the guy, “Okay, we can still do your ablation and you are going to see. Obviously you don’t want to do the other eye.” I put a contact lens in him and let the epithelium heal and usually I will put plugs in them too. I will just go ahead and plug them and let them tear and keep the surface nice and moist and go with it from that approach.

Daniel S. Durrie, MD: One thing we have found is that if you have those patients that either have a third of the cornea or the whole epithelium moves, if you just try to pile the epithelium back and kind of hope it is going to go okay, their course is very stormy

Wavefront and Emerging Refractive Technologies, pp. 97–105

Proceedings of the 51st Annual Symposium of the New Orleans Academy of Ophthalmology, New Orleans, LA, USA, February 22-24, 2002

edited by Jill B. Koury

© 2003 Kugler Publications, The Hague, The Netherlands

and will take a long time. I found that if you have those pieces that are moving or a flap tear, just take them off. If you haven’t tried that, it really helps you a lot. Then you can smooth the flap out and make sure of the edges, and you are less likely to get an ingrowth. You will get a little localized DLK and now you have some inflammation and you also have an epithelial defect. So I try to not put them on a lot of steroids. I think that, if you have a big flap epithelium, sometimes it is better to take it off rather than just kind of piling it back and hoping it sticks.

Steve G. Slade, MD, FACS: If you have a large epithelial flap, if it is hanging down like a filament, you can certainly remove it, but I would be cautious. It is almost like a LASIK. Any epithelium that you think will stay at all I would leave, especially over the edge, at the edge of the keratectomy. I am not worried about epithelium that goes from the flap itself, but I am worried about epithelium right at the edge of the flap. There are two other things as far as prevention or avoidance of these is concerned. One is that the keratome virtually never compresses the cornea as it goes in. Some keratomes are now being designed with zero compression heads where it doesn’t actually compress that and rub off the epithelium. I think that is an advantage. And this is also one of the things that a femtosecond keratome might have a role in. When we have one of those to do the first eye with and we have an epithelial abrasion, and it is always in the exact same place in the second eye (I think it’s embryological), we will do the second eye with a femtosecond laser because there is no motion across the cornea.

Ioannis G. Pallikaris, MD: I’d like to make a comment. I have done several thousand cases in the past ten years, and I have never had this kind of epithelial loss. And I am not saying that I am a very good surgeon, but I’d like to point out here that it is very much related to the way you are doing the cut in order to avoid this problem. It is probably a hydration problem, as you hydrate the cornea, what kind of keratome, but using several different kinds of keratomes, I probably had this problem once. It was a central epithelial defect. I often have peripheral ones, which is another issue, but not this one. And probably you have to avoid giving a lot of anesthetic, but something has happened here with this losing epithelium for sure.

Dr Schallhorn: One thing that Steve Brint told me early on, and which I found helped a bit, was that we give Refresh Tears or some kind of non-preservative tears every five minutes for the first twenty minutes or half hour before the procedure, and that seems to just keep the epithelium more moistened and smooth and not drying out. I think some of the anesthetic drops and then drying out a little bit makes it more prone to sloughing.

Marc Michelson, MD: One thing we look at very critically is that the moment when the epithelium comes off is usually on the reverse pass of the microkeratome. And I make sure that my nurse has lowered the suction or eliminated the suction on the machine, and we are constantly hydrating during that back pass. It’s a small thing, but it tends to help and we tend to not see as many epithelial defects.

Dr Schallhorn: The next complication can be related to patients who have an intraoperative epithelial defect, and that is epithelial ingrowth. We have probably all seen ingrowth, but it can be benign, not progressive, or it can be progressive, melting

the flap. I would like the panel to discuss the different management techniques for patients who have epithelial ingrowth.

Dr Slade: I have a comment and then a question to the panel. I don’t remove epithelium if it’s just a little bit and it’s not progressive. When I remove it: if it’s progressive, if it’s blocking vision, if it’s creating astigmatism (it can create a lot of astigmatism), or if you are getting corneal melt B those four reasons. Otherwise I think you can leave it. Someone came up to me who was using a scanning laser with a large blend zone or a large treatment zone such that it was occasionally treating the epithelium at the edge of the keratectomy when you lay the flap back, and they felt they were getting increased epithelial ingrowth. So this was not laser-specific; this applied to any laser. And lots of times we do, if you have a smaller bed, you are treating the epithelium with the blend. Theysaidtheythoughtthiswascausingthemtohaveanincreasedincidenceofepithelial ingrowth. Has anyone seen this?

Dr Stonecipher: I have had several people who have reported it to me. I have never seen it personally. But when I went back and looked at the specific cases, what they were doing was mostly hyperopic ablations, large treatment zones, making smaller flaps, and what was in and up was that they were getting edge ingrowth really because they were ablating deeper than the thickness of the epithelium. So, say your epithelium is 50-60 µm and they were doing treatments greater than that. I have never seen one in which you had like a 14 or 15 µm treatment, but when they went below the level of what would theoretically be your thickness of epithelium, I have seen that.

Dr Schallhorn: Any comment on techniques, if you determine that you want to remove that epithelium?

Dr Pallikaris: I remove, as Steve mentioned, in cases in which I have some problems, but in peripheral cases, I don’t remove it. But what I observe every time I am removing this epithelial growth is that the melting part of the epithelium is only a small space, but when you try to remove the epithelial cells you realize that there is a huge area around that is full of epithelium. So when you want to remove it, it does not stay on the melting part of the epithelium, but goes around and then you realize that you have a wide area with epithelium that is very nice, transparent. Once at the beginning of my career, I had done a very nice LASIK. A week later, the patient goes from B1.00 up to +8.00, a very clear cornea, and I could not understand why I had this change in the dioptrics within a week. So I decided to open up the flap and I realized that in between the flap I had a very nice layer of epithelium, and then when I looked at it with electron microscopy I found that it was very nicely located like the normal epithelium on the surface, so I had like an interface normal transparent epithelial layer not seen on the slit lamp. So think about it. Very often you have epithelial growth which you do not see, by the way.

Dr Schallhorn: It certainly is a lot larger than you think, and it is important to try to remove the epithelium from the back side of the flap, and also to look and see if there is a small area, perhaps a buttonhole, irregularities in the flap that may have caused this, in correcting it. How about another relatively common complication, DLK? Management modalities B do you change your management modality if you see DLK? I

know it is rarer now. It certainly can be related to microkeratome or sterilization issues, but if you see a DLK, what are your current management techniques?

Dr Durrie: The DLK we talked about was an interface contaminant, whether it was an endotoxin or poor sterilization, or those things, I think it is kind of going away. Actually, I have never seen a case of that in all the years I have been doing this, but I do these in a sterile operating room and use regular sterilization techniques. No, I have never seen a DLK of that contamination type. I think you can get rid of them if you make sure you don’t have contaminants on your instruments. What we all have is interface inflammation that can be from a localized epithelial defect or an area where someone had a previous peripheral inflammatory disease and they get some white cells there. And I think we need to differentiate those, at least on our little things we call interface inflammation something different than DLK, just so that we’re saying, “This is a contaminant, and this is just interface inflammation”. The secondary ones, they just go away, and maybe you increase the steroids slightly. But if you have something in your interface, that is bad. You may have to take it out and figure out how to not do that again. Fortunately, the incidence, I think, has dropped way down since people have become better at cleaning.

Dr Slade: One other caveat, if the DLK doesn’t follow the normal, typical course, which is resolving after a few days on heavy steroids, consider something else. I have seen three cases now that were referred in with mycobacterium, and they were treated for months as DLK, and then finally they started melting the cornea, and whatever. So be aware, it’s not always DLK.

Dr Durrie: On the way over here, Marc, another thing that can masquerade is steroidinduced intraocular pressure rises. I saw this on a physician, an ophthalmologist, who came in on whom I did an enhancement, and he went back and his partner measured him and he said he had some haze in the interface one day postop, so we increased his steroids, and I called him back and said, “Make sure you measure his pressure”. His pressure,measuringitperipherally,was60,andhetookhimoffthesteroidsandlowered his pressure and immediately it went away. So you can have an interface edema that can mask as DLK that you certainly don’t want to dump steroids on.

Dr Michelson: I’d like to mention a case I had just this year which I think might also be relatively rare. A patient who was about eight months out of postop LASIK and developed EKC and who was about three days into a rather acute EKC course, developed not only severe DLK, but also an infiltrate in the interlamellar space, and it reduced his vision rather significantly. Fortunately it reversed and he regained 20/20, but he was a late postop EKC patient who developed severe DLK.

Dr Krueger: Just a final comment. I think a lot of docs are sometimes afraid to lift a flap and irrigate, so they tend to follow it, and give lots of drops and stuff. If you see something that is lingering after about three days or thereabouts and it seems to be a grade II to III, you might as well just take them and irrigate underneath. Those steroids will help to stop more cells from coming in, but some of the existing cells, there can have been lytic enzyme effects, and it is much better to get rid of them than to have sequelaeofslightmeltingandsomehazedeveloping.Withthat,too,ifyouseesomething early on, the first postop day, and there are little bits of cells there, don’t have the

patient come back a week later, because they may come back with an incredible number of cells. We have seen a case in which it changed the whole topography to where it looked like a giant cone afterwards, and it was melting in a peripheral fashion just because of a DLK that wasn’t monitored and watched.

Dr Schallhorn: The next one, kind of a broad category, is the dry eye patient after LASIK, which is relatively common. From the panel’s standpoint, I am wondering about the managementofthis,punctalplugs,whenareyouapttoputapunctalplugintosomeone, or do you want to put it in preop, and kind of the management of dry eyes. How do you currently manage the dry eye patient?

Paolo Vinciguerra, MD: We see a tremendous improvement in patients treated with amino acid pills which promotes the number of keratocytes inside and then it seems most of the regrowth of the nerve inside by the confocal microscopy study. So the denervation induced by the cut and by the ablation can be improved in some way by amino acid.

Dr Stonecipher: I was going to say something along those lines. I have been doing dry eye research since 1984-1985, and have been involved in everything, and I think that obviously everyone does the punctal occlusion thing, and everyone puts them on nonpreserved tears and all that, but we have also been looking at lactoferrin levels and, in some of these patients, there are different ways to go, based on what their lactoferrin levels are, in treating them associated with that, and how you can differentiate things. We are now seeing that some of these patients will benefit from cyclosporin. Almost everywhere across this great country you can now get someone to make you a cyclosporin. Every now and then, you will get a postmenopausal female on whom you have operated, and it is November or December, and it is 20% humidity outside, and you have tried the steroid thing, and they are punctally occluded upper and lower. You might want to try cyclosporin being made up in like a 1% concentration and, in addition, these hydro-vitamins. The problem with these vitamins is they have a lot of fatty acids and a lot of things like cod liver oil in them, and a lot of your patients don’t like that, it causes them problems. But it is still something that is at least worth looking into. Finally, everyone always asks, where is Allergan in terms of the cyclosporin study. I was part of that. There were a few things that have been put on the front burner in front of that, and they are hoping that the cyclosporin preparation that we proved to do better will be available in early 2003. That is where they are now. So we will see.

Dr Slade: Dry eyes is really very climate-related. I think the best thing would be for any prospective LASIK patients to move to more humid climates, such as New Orleans or Houston. I think everyone would agree with that.

Dr Durrie: I don’t think Paolo is going to give this lecture here, so I want to kind of tell you a little bit more of what he said. The hydro eyes and the Omega 3 oils are one direction. What Paolo is really looking at is the high-dose mega amino acids that body builders use. As a matter of fact, his lecture is really good. Plus, he has shown with confocal microscopy and other things that it is really having an effect. I think we need to pay attention to a lot of these nutritional things. I was very impressed when I heard Paolo’s talk on that. It showed that we don’t understand nutrition at all. I asked him, “Well, what is the pill?” and it’s actually called ‘The Big One’. That is what the pill is

made up of, and it is just this great big amino acid horse pill that you get at the bodybuilder’s shop.

Dr Viniciguerra: Many things have changed. That was a preliminary study and the number of pills was too high. Nowadays, the solution is soluble in water that they take twice a day, Trium is the name. It is very easy to take. We also carried out some histological studies on eye bank corneas and just giving this to a different medium of storage, we see the epithelium regrow even in corneas preserved for graft. It was so impressive that we started doing it on patients and, after two months, most of the cases never complained any more about dry eyes. They have immediate improvement, progress improvement after suspension of the therapy at one month, and after they stop all complaints. It seems to be very easy to do.

Dr Schallhorn: From the panel’s standpoint, how many have used cyclosporin? How about flaxseed oil?

Dr Durrie: Flaxseed is an Omega 3 oil and it really does cause diarrhea, especially at this level. But if you use the straight Omega 3 fish oil tablets, they don’t give you nearly as many problems. I think those work extremely well. Joe Chalber has done some work on this, and we have seen that just taking the Omega 3 oils is quite helpful, and they are good for your arteries and help avoid strokes and everything else, and are not too hard to take.

Dr Stonecipher: One more simple thing on this that I forgot to say when I was talking about lactoferrin levels. Literally, doxycycline is a great drug and most people can tolerate it. For those people who have an evaporative dry eye because their lipid layer is bad, and we are talking about trying to supplement their lipid layer, a two-week course of doxycycline works really well in some of these patients and it is worth trying. It is just a simple old medicine that we forget about sometimes.

Dr Schallhorn: I am going to wrap it up with the flap striae and then we will go over a couple of other things. Postop striae in the flap B how would you decide whether to correct that surgically, and if so, techniques?

Dr Michelson: I decide to operate when the patients are complaining and you see them. What I find works best in my hands is to actually remove the epithelium and to put sterile water on the surface, use a smoothing technique, and you can actually see the striae evaporate over a course of about one to two minutes. One thing I’ve seen that rather surprised me is that, in a sector area of the corneal flap that may have striae, many times these flaps are not adherent to the underlying stroma. And you can actually see when you manipulate the cornea or the corneal flap that that segment is not adherent to the underlying stroma, even months later, and this is the origin or source of the flap striae.

Dr Stonecipher: I differ just a little. I define striae and folds and I think that everyone knows the difference in terms of striae versus folds, and the striae are those high myopes in whom you made this big divot in the cornea and you are trying to lay a curved flap in a valley now, and that is what I call a stria, which can or cannot be visually significant by our measurement techniques. Folds, I think you have to treat. I think that if you

have folds of any kind, and that is simply putting fluorescein in and you see folds, you have to treat them. We will probably all differ on how you treat these folds and what you do with them, but I think the time course is what is important too. So simply, if it’s the first postoperative day and you have a slipped flap or a moved flap, you may do one thing, whereas if you get a little longer in the course and someone refers one to you that is three or four weeks out or maybe months out, we may get into compression sutures and some other things that you have to try to stretch the flap back into place.

DrPallikaris:Iwouldliketomakeacommenthererelatingtomicrostriae,andifsomeone tries to remove the epithelium in any LASIK patient, he will realize that the surface of Bowman is not smooth any more. It looks like a desert, very fine lines. So any LASIK patient potentially has a microstria for sure. So how does this affect the optical quality? I don’t know, that’s another issue. But clinically we see that. When I have to retreat specificpatientswhohaveectasia,forexample,ortheyareundercorrectedforhyperopia using the stretching techniques B I mentioned this yesterday too B either a thermal keratoplasty approach or ICRs, with those kinds of techniques to stretch the cornea, I realize that the patient does have improvement in visual quality. This is very, very impressive. Even if we do not see striae on the slit lamp.

Dr Schallhorn: The last thing I’d like to do is to ask the panel to list one, two, or perhaps three things that they have done different surgically over the past year to reduce complications. What are the things they are now doing to reduce those complications? What are they doing differently now than they were a year ago?

Dr Pallikaris: Spending more time evaluating patients. This is something I have learned in the last 10 years. I note that every year I operate on fewer and fewer patients, and I try to find other techniques.

Dr Stonecipher: The one thing I want to say that I am doing a lot more of is in my postoperative regimen. You have people who come in and you evaluate them preoperatively and some of the postmenopausal females who have dry eyes, in North Carolinawhereitis20%humidityinFebruary,willwaituntilthesummertobeoperated on when it is more like 80 or 90%. That’s not the operative scene. My operating room is 70° and 50% humidity all the time. It is what they are living in and doing. I have discovered this because I operated on my brother, and he was sitting in there talking to a little lady preoperatively and she told him what to do and how to do it. He comes home and says, “Well, what am I supposed to do?” You have given him a little handout, you’ve given him everything. But I have now made out a little sheet suggesting four times a day for the tears and suggesting the drops (I use Pred Forte and Ocuflox now) four times a day, and I suggest the times. I hand it to the sponsor as well as to the patient. It is amazing that the sponsor is now beating them over the head and saying, “Hey, you have to use these drops”. Think about it. When you are sitting in there, the only thing you are worried about is whether this guy is going to make you blind. So you are not listening to anything the person is saying to you preoperatively, and then postoperatively, they don’t ever get it. These are people like us, lawyers, doctors, they should be able to listen. So I think handouts giving them suggested times, instead of just saying use the drops four times a day, really works.

Dr Vinciguerra: My suggestion is to do intraoperative topography. We now have a system that lies on the patient, and that gives some advantage. First of all, you can detect minor problems immediately and you can differentiate a problem coming from the healing process. So you can immediately define whether your laser is demonstrating some aging, some defects, and you can fix this immediately. It is totally different from making a refinement immediately, instead of asking the patient to let you do it after one week or two weeks. Then you can immediately detect the LASIK striae with these intraoperative controls, with Scheimflug, instead of refloating the postoperative day. So I am increasing the number of intraoperative controls.

Dr Durrie: I’d just like to echo operating on the correct patients. I have really changed the way I do the whole evaluation of the patient, as I now look for a reason not to do surgery on every patient who comes in, and I talk to them that way. I get more referrals from the people I tell not to do surgery than I do from the ones I do surgery on now. Because if I come in and say, “You should wait for new technology” or “Your eyes are too dry”, or as Karl said, “We need to do you in the summer, not now, because the humidity is going to be better”, or “You need to clean your eyelashes and you need to go on these nutritional things”. I would probably sign up 50-55% of the people I see now. I used to sign up 80% of the patients I saw, and I think that caused more expectations and problems than putting them off a bit longer. So, I think we are all heading toward becoming more conservative.

Dr Krueger: One thing I have actually done this past year, in addition to what Dan is saying, is spending time and actually telling people no, that brings more patients in. But I measure flap thickness in every patient I do. So, I measure right at the time of surgery, the central pachymetry, then I make the flap, then I measure the residual stromal bed, and my tech does a quick calculation and reads off and tells me what the flap thickness is. So I know what the residual bed is and I know how thick my flap was, and I have a good idea about whether my microkeratome is working properly. This is very helpful because, if I get a very thin flap on the first pass or first eye, I change the blade when I go to the second eye, because it is sort of a trend and it has been seen that second eyes are often thinner. And I don’t want to take the chance of getting a very thin flap that could be a buttonhole or something like that.

Dr Slade: The one thing I’ve changed, the best thing I’ve done in the past year, and probably a lot of you do this, is that I carefully slit lamp every single patient, like 15, 20, 30 minutes after surgery. I do the preop on the patient getting ready to operate, then I do the surgery, and then come back and see the patient I’ve just operated on. How many people do that? Okay, good news, fine. Ahead of the curve here. I always used to see them just at one day postop, but seeing them in the first 30 minutes, you can find fibers, all sorts of stuff. It is very helpful.

Dr Schallhorn: From my own perspective, I think the couple of things I am doing differently is that I’m always doing intraoperative pachymetry now, probably over the last year and a half, and am writing that down so that I know exactly what the bed is. I find this very useful for anyone pushing the limit of stromal bed remaining. It is also great to know if you want to do an enhancement. I carefully adjust nomograms for the different optical zone sizes. I certainly do that now. I find that I am more apt to do

PRK on patients who were maybe questionable LASIK, or is that a little bit of basement membrane dystrophy? or thin cornea? Am I pushing the edge of the envelope? Yes, I will have 250 remaining, but there is not enough for an enhancement with the thinnest blade. I have a tendency, I think, over the past year or so to do more PRK in that setting.