Ординатура / Офтальмология / Английские материалы / Mastering Corneal Collagen Cross Linking Techniques (C3-R, CCL, CxL)_Garg_2009

Our experience showed us only alcohol application without epithelium removal, prove riboflavin penetration more. Under sterile conditions 20% alcohol is applied for 25 seconds similar with LASEK procedure. Initially 0.5% proparacaine and 2% pilocarpine eyedrops are administered every 2 minutes and 5 minutes, respectively for 30 minutes; for anesthesia, miosis in order to minimize exposure of the lens and decrease photosensitivity. Then, riboflavin drops (0.1% riboflavin-5-phosphate and 20% dextran) are administered every 3 minutes, for 30 minutes. Penetration of riboflavin to the corneal stroma and anterior chamber was confirmed by slit-lamp examination. Then, collagen CXL procedure is performed by exposing the central 7.0 mm cornea to UV-A light (3.0 mW/cm2, at 370 nm), for 30 minutes, This is combined with continued topical application of riboflavin solution (0.1% riboflavin-5-phosphate and dextran) every 3 minutes, without removal of epithelium (Figures 18.5A and B); similar to the technique described by Chan et al.24 Intact epithelium led to less patient discomfort after procedure. After treatment, artificial tears are used for a few days.

In this study25 twenty-five eyes of 17 patients had INTACS implantation and then underwent collagen CXL between June 2007 and December 2007. Initial and follow-up examinations, surgical procedures were performed. Collagen CXL was performed 3,98 ± 5,7

months after the INTACS implantation. The inclusion criteria were bilateral keratoconus without corneal scarring, contact lens intolerance, corneal thickness greater than 400 µm and endothelial cell count more than 3000/mm2. All patients were examined initially, 3 months after INTACS implantation, and 2 months after collagen CXL for uncorrected and best corrected visual acuity (UCVA and BCVA) using Standard Snellen chart. Corneal topography was performed using Pentacam (Oculus Opticgerate GMBH).

We retrospectively obtained the data from before INTACS implantation, after INTACS just prior to crosslinking (1st visit; mean time interval: 3,98 ± 5,7 months) and at 2 months after cross-linking (2nd visit; mean time interval : 2,67 ± 2,67 months). Results were compared from before INTACS to after INTACS and from after INTACS/before cross-linking to after crosslinking.

Surgical Technique

INTACS were inserted to 70% depth of cornea in all eyes using Intralase (Intralase Corporation, Irvine CA). Peripheral pachymetry was performed in all cases to ensure sufficient corneal thickness and placement of INTACS to the appropriate depth. The pulse duration was 600 femtoseconds, with the inner to outer diameter of the INTACS tunnel set from 6.7mm to 8.2 mm. Spot size was 1 micron and the energy was 6 microjoules. INTACS segments were implanted inferiorly and superiorly based on patients’ preoperative spherical equivalent and the location of the cone. A thicker segment was placed inferiorly, and a thinner segment was placed superiorly to preferentially flatten the inferior cornea in eyes with asymmetric cone.

All eyes underwent CXL procedure 3,98 ± 5,7 months after INTACS insertion (supplies obtained from Peschke Meditrade GmbH). Initially 0.5% proparacaine and 2% pilocarpine eye drops were administered every 2 minutes and 5 minutes, respectively for 30 minutes; for anesthesia, miosis in order to minimize exposure of the lens and decrease photosensitivity. Then, riboflavin drops (0.1% riboflavin-5-phosphate and 20% dextran) were administered every 3 minutes, for 30 minutes. Penetration of riboflavin to the corneal stroma and anterior chamber was confirmed by slit-lamp examination. Then, collagen CXL procedure was performed by exposing the central 7.0 mm cornea to UV-A light (3.0 mW/cm2, at 370 nm), for 30 minutes,

This was combined with continued topical application of riboflavin solution (0.1% riboflavin-5-phosphate and dextran) every 3 minutes, without removal of epithelium; similar to the technique described by Chan et al.24 Intact epithelium led to less patient discomfort after procedure. After treatment, artificial tears were used for a few days.

Statistical Analysis

Preoperative data were compared with data obtained 3,98 months after INTACS implantation and the latter was compared with data obtained 2,67 months after CXL. Paired sample T test was used to compare the parameters (UCVA, BCVA, spherical and cylinder values, steepest K value, mean-K value).

RESULTS

The mean-age of the patients was 25,14 ± 7,11 (range:16-39). Preoperative mean UCVA and BCVA were 1.61 ±1.23 (range: 0,1-4) and 4.18 ±2.09 (range:0,2-8) snellen lines respectively. Mean preoperative K values, spherical and cylindrical values were 49.9D ± 4.59 D (range: 40-58 D) ; -3.89 ±4.89 D (range: -12- 0) and -3.74 ± 1.90 D (range: -8- (-1)), respectively.

After INTACS treatment, mean UCVA and BCVA were 3,58 ± 2,29 D (range: 0,5-10) and 6,54 ±2.02 D (range:2-10) respectively. Mean preoperative K values, spherical and cylindrical values were 47.60 D ± 3.68

D (range: 39,4 - 54,8 D) ; -1,90 ± 2,87 D (range: -3- (-6)) and -3.52 ± 1.65 D (range: -1- (-8)), respectively. After cross-linking, mean UCVA and BCVA were 4.80

± 2.00 D (range: 1-10); 7.27 ± 2.02 D (range:3-10) respectively and mean K, spherical and cylindrical values were 47.46 ± 3.54 D (range:40-54), 1,68 ± 2.18 D (range:-5-(2)) and -3.11 ±2.32 D (range: -6 – (3)), respectively.

The preoperative, post-operative 1st visit (3,98 months after INTACS implantation) and post-operative 2nd visit (2,67 months after collagen CXL) parameters are shown in Table 18.1. The mean follow-up was 3.98 months after INTACS and 2.67 months after CXL. INTACS treatment was significantly effective on each parameter except the cylinder values. There was improvement in UCVA, BCVA, manifest refraction, steepest K value, mean-K values after CXL treatment; however it reached significance only for UCVA, BCVA and spherical values (p<0.05).

The mean changes in visual acuity, manifest refraction, and keratometry from before INTACS to 4 months after INTACS summarized in Table 18.2. The post-INTACS values served as the baseline for the CXL to 2 months after CXL are also presented INTACS alone resulted in an 2-line improvement in UCVA and BCVA. After CXL, an additional line of UCVA and BCVA was gained. The gain in BCVA was significant; whereas, the gain in UCVA was not. INTACS alone resulted in decrease in myopia with a 2 D decrease in sphere and nearly 0,5 D decrease in cylinder. CXL

resulted in another 0,50 D improvement in sphere and only a small (0,15 D) decrease in cylinder. Neither of these changes were significant. INTACS alone achieved a mean 2,22 D flattening of mean K values and -1,28 D flattening of the K steep values. Additional flattening of the keratometric values was observed after CXL, with mean K values decreasing significantly by an average of 0,35 D and K steep decreasing by 0,76 D (Figs 18.6 to 18.8).

CONCLUSION

There are many reports in keratoconus treatment using INTACS (6-9,23-26). We reported , the mean UCVA and BCVA increased significantly to 3.29 ± 2.64 (Snellen lines) and 6.02 ± 2.70 (Snellen lines) respectively after INTACS implantation. In this study, the mean K reading was 51.56 ± 5.22 D at the preoperative examination. At 1-year after implantation, the mean keratometry reading had decreased to 47.66

± 4.30 D.26

The first clinical study on the CXL treatment of keratoconus was performed by Wollensak.14 This new treatment is aimed at the pathogenic cause of keratoconus and changes intrinsic properties of corneal collagen. In this 3-year study, 22 patients with progressive keratoconus were treated with riboflavin and UVA. CXL had a favorable effect on all treated eyes. In 16 eyes (72%) , there was also a slight reversal and flattening of keratoconus by two diopters. Best

116 corrected visual acuity improved slightly in 15 eyes

(68%). According to the results of CXL treatment, regression of the disease was achieved in 70% of eyes, with a reduction of the maximal keratometry readings by 2.01 D and of the refractive error by 1.14 D.14 In our study, UCVA improved by 1.2 lines and mean K value decreased by 0.35 D, 2 months after CXL treatment. Caporossi et al,27 showed a mean K reduction of 2,1 D which is more than our result when we compare only CXL treatment change. Braun et al.22 reported stabilization of keratoconus in all 22 patients and 27 eyes, and regression by 2 D in 12 eyes (44%) after CXL treatment. In our study, when CXL was performed after INTACS implantation, UCVA improved by 1,2 lines and mean-K value decreased by 0,35 D, 2 months after CXL treatment. Pre-operative mean UCVA increased from 1.61 lines to 4.8 lines; and mean K value decreased from 49.8 D to 47.2 D after INTACS / CXL. Our improvement in refractive and topographic results with INTACS and CXL are not as favorable as those reported with CXL treatment alone.

Chan et al,24 reported the first study about combined treatment INTACS and CXL. They showed that the combination of CXL with INTACS led to better results than INTACS insertion alone, as proved by greater reductions in manifest refraction, steep K and average K. In their study, mean changes in UCVA, BCVA, sphere and mean-K values were 6.5 lines, 1 lines, 0.12 D and 1.34 D respectively after INTACS with CXL; and 9.5 lines, 1 line, 0.25 D and 0.21 D respectively after only INTACS treatment. They concluded that this might be the result of

biomechanical coupling from local collagen changes around the segments.

CXL with the epithelium removed versus transepithelial treatment is another controversial issue. Applied riboflavin must diffuse into the cornea stroma for treatment efficiency. The intact epithelium is barrier that slows the absorbtion of riboflavin into the cornea so it penetrates slowly and incompletely.27 CXL treatment without removing epithelium causes inadequate penetration of riboflavin and therefore enhances ultraviolet (UV) penetration and results in possible cell damage. Pinelli et al reported their 6 months’ CXL results and found comparable outcomes without removal of epithelium in terms of changes in keratometry, vision and endothelial cell count ( The Italian Refractive Surgery Society results using C3R, 2nd International Congress on CXL, Zurich 2006). Sharma and Boxer Wachler also reported similiar results after CXL without removing epithelium.(Corneal collagen CXL with riboflavin for corneal stabilization. American Academy of Ophthalmology Annual meeting October 2005).

Riboflavin absorbs UV and reduces penetration; the absorption then causes cytotoxic reaction. Riboflavin sensitizes the cornea to UV, by ten times. It would have been ideal, if the riboflavin penetration could be limited to the first 300 microns of the cornea, to spare the endothelium. Limited penetration of riboflavin in superior part of cornea, in eyes with intact epithelium may be actually safer in UV-A application. Podskochy et al,29 showed increased keratocyte damage with ultraviolet light when the epithelium was removed. This study reported that epithelium may play a significant role in absorbing UV-A and thus protect cornea and deeper structures from damage.

In our study, treating keratoconus with INTACS followed by CXL resulted in more regular topography with visual improvement. There was significant improvement in UCVA and BCVA values after CXL. On the other hand, mean-K values and BCVA were statistically better after initial INTACS treatment. In our hands, CXL treatment after INTACS was not as effective on mean-K values and on manifest refraction as compared to previous studies.24 On the other hand, other studies showed INTACS combined with CXL is a more effective strategy than CXL alone or INTACS alone

118 in respect to UCVA, BCVA30.

Recently Chan et al (Chan C, Hodge C, Sutton G. Collagen CXL with INTACS, WOC , Hong-Kong, 2008) compared outcomes of same day CXL and INTACS, INTACS alone and CXL 6 months after INTACS treatment. They showed that there was significant difference among 3 groups and same day CXL and INTACS treatment had better results.

In advanced cases of keratoconus, CXL may be considered after INTACS implantation as to provide slight improvement in refractive and visual results with possible stabilisation effect and without significant adverse consequences. This study is limited by the number of patients and short term follow-up; further controlled studies with longer follow-up are needed.

REFERENCES

1.Rabinowitz YS, Nesburn AB, McDonnell PJ. Videokeratography of the fellow eye in unilateral keratoconus. Ophthalmology 1993;100:181-86.

2.Li X, Rabinowitz YS, Rasheed K, Yang H. Longitudinal study of the normal eyes in unilateral keratoconus. Ophthalmology 2004;111(3):440-46.

3.Colin J, Cochner B, Savary G, et al. Correcting keratoconus with intracorneal rings. J Cataract Refract Surg 2000;26:1117-22.

4.Alio JL, Shabayek MH. Intracorneal ring segments (INTACS) for keratoconus correction: long term follow-up. J Cataract Refract Surg 2006;32:978-85.

5.Barraquer JI. Modification of refraction by means of intracorneal inclusion. Int Ophthalmol Clin 1966;6:5378.

6.Fleming JR, Reynolds Al, Kilmer L. The intrastromal corneal ring-two cases in rabbits. J Refract Surg 1987;3:227-32.

7.Andreassen TT, Simonsen AH, Oxlund H. Biomechanical properties of keratoconus and normal corneas. Exp Eye Res 1980;31:435-41.

8.Nash IS, Greene PR, Foster CS. Comparison of mechanical properties of keratoconus and normal corneas. Exp Eye Res 1982;35:413-24.

9.Roberts C. Biomechanics of INTACS in keratoconus. Intracorneal Ring Segments and Alternative Treatments for Corneal Ectatic Diseases. ed. Colin J, Ertan A Kudret Göz Yayýnlarý, Ankara 2007;159-66.

10.Ertan A, J. Colin. “Intracorneal rings for keratoconus and keratectasia,” J. Cataract Refract Surg 2007;33:1303-14.

11.Jester JV, Moller-Pedersen T, Huang J, et al. The cellular basis of corneal transparency evidence for “corneal cristallins”. J Cell Sci 1999;112:613-22.

12.Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984:28:293-322.

13.Rabinowitz YS. Keratoconus. Surv Ophthalmol 1998:42:217-319.

14.Wollensak G, Spoerl E, Seiler T. Riboflavin ultraviolet – A

– induced collagen cross-linking for the treatment of keratoconus. Am J Ophthalmol 2003;135:620-27.

15.Wollensak G, Sporl E, Seiler T. Treatment of keratoconus by collagen Cross-lýnkýng. Ophthalmology 2003;100:4449.

16.Wollensak G. Cross-lýnkýng treatment of progressive keratoconus: new hope. Curr Opin Ophthalmol 2006;17(4):356-60.

17.Sung H-W, Chang W-H, Ma C-Y, Lee M-H. Crosslýnkýng of biological tissues using genipin and/or carbodiimide. J Biomed Mater Res 2003;64A:427-38.

18.Krishna CM, Uppuluri S, Riesz P, et al. A study of the photodynamic efficiencies of some eye lens constituents. Photochem Photobiol 1991;54:51-58.

19.Lang JC. Ocular drug delivery: Conventional ocular formulations. Adv Drug Deliv Rev 1995;16;39.

20.Prausnitz MR, Noonan JS. Permeability of cornea, sclera and conjunctiva: a literature analysis for drug delivery to the eye. J Pharm Sci 1998;87(12):1479-88.

21.Kymionis GD, Portaliou DM, Bouzoukis DI, et al. Herpetic keratitis with iritis after corneal Cross-lýnkýng with riboflavin and ultraviolet A for keratoconus. J Cataract Refract Surg 2007;33:1982-84.

22.Spoerl E, Mrochen M, Sliney D, et al. Safety of UVARiboflavin Cross-linking of the Cornea. Cornea 2007;26:385-89.

23.Colin CKC, Wachler BSB. Corneal Collagen Cross-lýnkýng with Riboflavin and UVA. Intracorneal Ring Segments and Alternative Treatments for Corneal Ectatic Diseases. ed. Colin J, Ertan A, Kudret Göz Yayýnlarý, Ankara 2007;16787.

24.Chan CKC, Sharma M, Wachler BSB. Effect of inferiorsegment INTACS with and without C3-R on keratoconus. J Cataract Refract Surg 2007;33:75-80.

25.Ertan A, Karacal H, Kamburoglu G. Refractive and Topographic Results of Transepithelial Cross-linking Treatment in Eyes with INTACS. Cornea (in press).

26.Ertan A, Kamburoðlu G, Bahadýr M. INTACS insertion with the femtosecond laser for the management of keratoconus: One-year results. J Cataract Refract Surg 2006;32:2039-42.

27.Caporossi A, Baiocchi S, Mazzotta C, Traversi C, Caporossi T. Parasurgical therapy for keratoconus by riboflavinultraviolet type A rays induced cross-linking of corneal collagen. Preliminary refractive results in an Italian study. J Cataract Refract Surg 2006;32:837-45.

28.Krachmer JH, Feder RS, Belin MW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol 1984:28:293-322.

29.Podsckochy A, Gan L, Fagerholm P. Apoptosis in UVexposed rabbit corneas. Cornea 2000;19(1):99-103.

30.Wollensak G, Wilsch M, Spoerl E, Seiler T. Collagen fiber diameter in the rabbit cornea after collagen Cross-linking by riboflavin/UVA. Cornea 2004;23(5):503-507.

INTRODUCTION

Keratoconus is a bilateral, noninflammatory corneal disorder that leads to inferior paracentral corneal thinning, inferior corneal steepening, and irregular astigmatism.1 Although the etiology remains uncertain 14% of cases are associated with a genetic predisposition.

Keratoconic patients could present with complaints of decreased vision, glare, photophbia, and monocular diplopia. External clinical signs of keratoconus include Munson’s sign (protrusion of inferior lid on down gaze) and Rizutti’s sign (conical reflection on the nasal cornea when light is shone temporally). Slit lamp presentations of keratoconus include inferior paracentral corneal thinning, presence of an ectatic cone within the area of corneal thinning, inferior corneal steepening,Vogt striae (vertical stress lines in the posterior stroma), and a Fleischer ring (iron deposits in the basal layer of the corneal basal epithelium), linear scars can also be seen as result of breaks in Bowman’s layer. Breaks in Descemet’s membrane can lead to stromal edema and corneal hydrops with intrastromal clefts and vascularization. Resolution of corneal hydrops can lead to corneal scarring. Patients with Keratoconus also have scissoring on retinoscopy and the presence of Charleaux oil droplet reflex, a bright reflex from conical apex surrounded by a dark circular shadow produced by the corneal ectasia.

There are various methods for grading of keratoconus worldwide. The KISA%, created by Rabinowitz provides an algorithm to quantify results from computerized videokeratoscopy to classify whether a patient has keratoconus.2 McMahon and colleagues and the Collaborative Longitudinal Evaluation of Keratoconus (CLEK) have proposed a method called keratoconus severity score (KSS) for grading of the severity of kerraoconus.3 New Pentacam Technology (Oculus Inc.) provides parameters that can be further correlated and associated with related anatomy for a more descript diagnostic acumen along with a keratoconus detection software based on relative indices.4-5

In this chapter, I shall introduce my classification system that is used in my practice to apply Excimer Laser in a surface ablative (ASA/ PRK) mode for keratoconus and related ectatic disorders.6-7

GULANI CLASSIFICATION SYSTEM FOR LASER SURGERY IN KERATOCONUS

Laser as Primary Treatment

(In this subset, the patient is informed that we can strive for vision directly with the laser keeping the surgical interventions noted in Level II as back up plan to be applied in single or combined approaches to address any complication induced or progression of cone if needed)

Class I

Clear Cornea Class II Scarred Cornea

Laser as Staged Secondary Treatment

Class I

Following corneal surgery:

a.INTACS

b.Lamellar Keratoplasty

c.Penetrating Keratoplasty

d.C3-R cross-linking

e.Conductive Keratoplasty

Class II

Following intraocular surgery:

a.Phakic Implant

1.Anterior

2.Posterior

b.Cataract surgery with lens Implant

1.Monofocal

2.Toric

3.Presbyopia-corrective

Each case of keratoconus is unique. From their appearance to their topographies and even their refractions, optical effects and aberrations. Over years of numerous clinical and surgical encounters, I found one thing consistent in all of them- “Irregular Astigmatism.”

Since I am a firm believer in logic and clinical sense over market-hyped terminologies, I decided to personally approach every case of keratoconus as an asymmetric, high irregular astigmatism associated with other refractive errors ie. Myopia, hyperopia and or presbyopia.8-9

Lets first understand why we can or even should use Excimer Laser in a case of proven Keratoconus:

Patients with Keratoconus are frustrated with their vision and resultant life style (especially when they have exhausted their options with glasses and contact lenses). Once they have passed the stage of such nonsurgical options, they are facing surgery to rehabilitate their vision.

Among surgical options presented in the current times:

1.Corneal transplant (invasive surgery with long term adverse impact including life style restriction and also little ability to bring patients to uncorrected 20/20 vision).

2.INTACS: Excellent, reversible, less invasive surgery (may even delay or avoid transplant in many cases), but unpredictable in most cases and

majority of cases shall need contact lenses and or glasses after the surgery to help patients see.

Given that these patients in most cases are otherwise healthy young adults at the prime of their professional and personal stage in life, we must look at them as people rather than as an eyeball with a book diagnosis.

We must therefore want to provide them the best vision they are capable of and that too without dependence on glasses and contact lenses if possible. Remembering again that they are at their most productive stages of their life and just like our refractive patients must be encouraged to lead a visually independent life.

Here, we need to balance our desire to provide an enhanced lifestyle with our honest intention to keep safety for these patients utmost in our minds.

If selecting a choice of INTACS for these patients since compared to a corneal transplant it is less invasive and more promising visually, we are doing the right thing and explaining to patients that they will come close to 20/40 and also that they shall need contact lenses and or glasses. This is a fair choice for someone who despite a hard contact lens trial does not see better than 20/40 preoperatively.

But what about the keratoconic patient who has passed the non-surgical option (CLs and glasses) stage and yet sees 20/20 best corrected?

In such cases, how are we justified in doing an approved procedure like INTACS (since we have to do something now that this patient cannot function

122 with contact lenses or glasses) to make their vision

worse ie.20/40 from their preoperative potential of 20/20?

This is where I find a place for the Excimer Laser.

Using the Excimer Laser in a surface mode (no LASIK in any case or any flap cutting) we can address the Keratoconus as what I call “Astigmatism gone wild” to “Tame” it to a shape resulting in excellent unaided vision.

Yes, theoretically the Excimer Laser will remove tissue and so accelerate the Keratoconus but we also delivering 20/20 unaided vision (remember this 20/ 20 may not ever match the 20/20 of our simple Lasik cases but coming to unaided 20/20 from legal blindness for a Keratoconus patient is visibly, sheer ecstacy) to these very affected patients for the first time in their life.

Here is the discussion with the patient: This is an option because you do meet the criteria for Laser surgery. If after laser surgery (no one can guarantee the duration that this will last) your vision does drop from 20/20 to 20/40 or worse either by natural progression or by the Laser surgery that you had then you fit the criteria for INTACS surgery.

Again, keeping in synch with my corneoplastique concepts, all of the mentioned surgeries available out there can always be used a back up. The patient never loses candidacy for them.

This discussion underscores the honest desire to help keratoconic patients lead a productive life of visual freedom knowing that there are back up plans in place.

Also with the application of Collagen Cross-linking (C3-R) , we may be able to arrest these keratoconic corneas after Laser Surgery in the final shape created to prevent progression in the future.

So keeping the above discussion in mind lets see how to apply these concepts in everyday practice.

I have used technologies including Pentacam anterior segment analyzer, multiple types of corneal topographers, wavefront technologies, Optec6500 and Visual simulators that zero in on cases that are obvious. Nevertheless, the Keratometer, Refractive retinoscopy and hard contact lens trial are a very important adjunct forming the mainstay of detection, grading and treatment selection.10-11

Simply put, if we start approaching every keratoconus as a form irregular astigmatism, we can apply the methodology of thought process and surgical

planning towards excellent visual outcomes. The corneal surface can be recontoured with an excimer laser in cases of keratoconus. This approach of correcting corneal architecture and finally shaping the contour with an Excimer Laser falls under the realm of my concept of Corneoplastique™.12-15

Numerous studies in scientific literature have investigated the use of laser treatment for keratoconus to give patients better and more comfortable vision with and without glasses or soft contact lenses. In these studies, the authors hope to avoid or delay the need for corneal transplant in keratoconus eyes, giving these patients better vision with and without glasses or soft contact lenses.16 Further more, it was found that Excimer laser surgery can improve vision and the ability to wear contact lenses, and does not interfere with subsequent corneal transplantation surgery.17 The downside to PRK is that it is not a standard treatment for keratoconus.

Rather, it is controversial because the procedure thins out the cornea. In keratoconus, the cornea is already thin and unstable and additional tissue removal can cause further progressive distortion. However, the Excimer laser may have potential therapeutic benefit in removing certain corneal scars. Some studies suggest that PRK may have a role in very mild and stable sub clinical keratoconus. Regardless, Excimer treatment in these instances is done selectively on a case-by-case basis.

I have successfully treated all types of keratoconus (the grade of severity does not matter as much as the parameters listed below) with surface laser vision surgery (ASA/PRK) by simply approaching them as a case of assymteric irregular astigmatism.

We have devised a set of criteria for Excimer Laser PRK surgery for Keratoconus.

GulaniNordan criteria for Laser PRK in Keratoconus:

•Patient is symptomatic with poor visual acuity and double vision or glare and cannot tolerate contact lenses (meaning the options of gasses or contact lenses has run out for any number of reasons).

•Clinical examination and signs suggesting corneal shape irregularity.

•Best corrected visual acuity of 20/30-20 (even if with hard contact lens trial). Best corrected vision below 20/40 would indicate INTACS.

•Refraction is stable (with review of prior documented exams).

•Astigmatism Higher than Myopia/ Hyperopia preferred.

•Corneal thickness is more than 400 μm in the thinnest part and also after laser shall be preferably not less than 350.

•Corneal scar even if present is less than the anterior one third in depth.18

•Patient ‘s understanding that using the Excimer laser is an “off-label” use and that if for some reason (due to laser or natural progression) if their

keratoconus worsens then they would be candidates for INTACS/ LK/ PKP in that order of decreasing selection.

If these criteria are met, I design a plan to correct this corneal shape and surface irregularity with the Excimer laser.

Even though I have treated practically every grade and combination of keratoconus with or without associated surgeries in stages or previously done elsewhere, in this chapter I shall limit myself to a discussion for primary laser PRK on Keratoconus and briefly mention the spectrum of Laser applications in combination approaches for the full spectrum of Keratoconus surgical care.

DISCUSSION AND RESULTS

All the cases were confirmed Keratoconus with present day criteria inclusive of topography and we did not differentiate treatment based on stage. Rather, we used my consistent approach based on visual potential and corneoplastique approach along with the classification system.

In this study we included 14eyes of 10 patients (9 males and 5 females) ranging in age from 20-66 years old with follow-up ranging from 6 months to 3 years.

Each of these patients underwent Surface Excimer Lasr (PRK / ASA) using standard protocol. No variance from my PRK technique was used in any of these cases.19 Following a normal PRK postoperative course, 13 out of 14 eyes achieved uncorrected vision of 20/ 20, one of the fourteen eyes achieved uncorrected vision of 20/40 (which was her best corrected vision preoperatively due to amblyopia) and 6 eyes of the 13 eyes at 20/20 achieved uncorrected vision of 20/15 (Figs 19.1 and 19.2A and B).

The point I want to stress here is that the postoperative evaluation of success of this treatment is 123