Ординатура / Офтальмология / Английские материалы / Mastering theTechniques of Lens Based Refractive Surgery (Phakic IOLs)_Garg, Alio, Dementiev_2005

Figure 15.2: Type B toric Artisan

SURGICAL TECHNIQUE

The surgical technique of implantation of toric Artisan follows the same steps as spherical Artisan, except that is very important that the IOL is implanted in the correct axis. The routine surgery is as follows:

a.Mark the axis of cylinder

b.Constrict the pupil (1 drop of pilocarpine 15 minutes before surgery)

c.Peribulbar or general anesthesia (avoid Topical)

d.Two sideports

e.Main incision (5.2 mm)

f.Fill AC with viscoelastic (prefer low density cohesive)

g.Introduce Artisan and rotate it to position

h.Enclavate Artisan in both sides with needle (grasp sufficient amount of tissue)

i.Perform iridectomy/iridotomy

j.Clean the visco completely (passive irrigation or I/A)

k.Astigmatic free suture

As we see from these guidelines, points (a) and (k)

make all the difference if we want to be successful with toric Artisan. It is very important that the IOL is implanted in the correct axis. It is known, that if there is a misalignment of 15º, the effect will be reduced by 50 percent. So it is very important, prior to surgery to mark with precision the site of the iris where the IOL will be

implanted. There are three ways of doing it, depending mostly on the color of the iris and surgeon’s experience. The easiest is mark the limbus with a pen. The only drawback of this procedure is that, we must be sure that during cleaning procedures of the eye, the marks do not disappear. Another option is to mark the iris enclavation site with argon or YAG laser spots. It important to note that both limbal or iris laser marks must be done with the patient sitting to avoid the ciclotorsion induced when the patient is lying down. The third method to do it is the so-called cartography of the iris. In this method (easier in blue irises) a photograph of the iris is taken and some peculiarities of the iris tissue are noted in the enclavation site.

Another key issue for success with toric Artisan besides correct positioning of the IOL is to perform an astigmatic free suture. This is not always easy because as stated before we need a 5.2 mm incision. How to achieve an astigmatic neutral suture largely depends on the experience of the surgeon, but there are some useful tips like performing a more posterior incision (limbal or even with a small scleral tunnel, avoiding clear corneal incisions) and performing continuous suture instead of separate sutures. Figure 15.3 shows a toric Artisan successfully implanted.

Figure 15.3: Toric Artisan

RESULTS

The European Multicenter Study coordinated by Burkhard Dick (Germany) was conducted in 16 centers and included 70 eyes. In the myopic group the pre-op cylinder was –3.74 ± 1.09 and post-op was 0.63 ± 0.53. Similar results were found in the hyperopic group; pre-op cylinder was 3.70 ± 1.05 and post-op was 0.77 ± 0.64.

Our personal experience shows also very good results with several cases of correction of 7 diopters of cylinder, but with some cases of induced astigmatism. Better management of sutures is the key to avoid that.

COMPLICATIONS

The complications of toric Artisan are very few and not different from classical Artisan. Please refer to the chapter “Complications of Phakic IOLs”.

TORIC ARTISAN IN SPECIAL CASES

We have been using toric Artisan with high success, also in difficult and complicated cases. When selecting eyes for refractive surgery, we often come across with eyes with subclinical keratoconus or full keratoconus (with good visual acuity). These eyes are an absolute contraindication to corneal laser surgery. Sometimes there is an important spherical error,but most of the times we find a spherocylindrical ametropia. These cases are

a good indication for toric IOLs. Also we find patients that have been previously submitted to Lasik or PRK for high ametropias and still have residual spherocylindrical errors, bit with a thin cornea. Again in these cases toric Artisan is the solution.

A last comment about high astigmatism after penetrating keratoplasty. Lasik surgery has been performed with different degrees of success. In our hands the results have been erratic with important regression in many cases. On the other hand implantation of toric Artisan in these eyes showed very promising results with improvement in lines of BCVA in most patients.

CONCLUSIONS

Toric Artisan is a phakic IOL associated with few complications and good results in the correction of both spherical and cylindrical errors. However, two pitfalls can darken this bright picture. First it is very important, that the IOL is positioned correctly. One of the advantages of this IOL is that once in place it does NOT move. The other possible pitfall is that we can induce astigmatism. This problem will disappear in the future once we have available a Toric Artiflex (foldable) that will only need a 3.2 mm incision.

Nevertheless and despite its present limitations the Toric Artisan is a very useful and safe tool to solve the problem of spherocylindrical errors and specially in cases where bioptics is impossible.

BO Phillipson (Sweden)

INTRODUCTION

The PRLTM is made of a new silicone material with a high refractive index of 1.46 and low gravity of 0.99. The lens material is soft, elastic and hydrophobic. The width of the lens is 6 mm, for correction of myopia the length is 11.3 mm or 10.8 mm and for hyperopia the length is 10.6 mm. The optic diameter varies from 4.5 to 5 mm depending on the dioptric power for correction of myopia. The lens is very thin and easily foldable (Fig. 16.1). The curvature of the lens is similar to that of the crystalline lens preventing it touching the crystalline lens. The PRL floats over the crystalline lens letting aqueous humour easily pass under the PRL without interfering with the metabolism of the crystalline lens. The lens comes in powers from –3 to –20 for myopia. There is also a hyperopic lens with an optic diameter of 4.0 mm, and powers from +3 to +15. Both myopic and the hyperopic PRL lenses have power increments of 0.5 D.

The original idea of the lens was given by Drs V Zuev and S Fyodorov at the Moscow Research Eye Institute who proposed a new phakic silicone lens in 1986. This

lens has been improved in all aspects and was moved over to the United States and produced by Medennium Inc. and distributed by Ciba Vision Corp. This lens is easily implanted through a 3.0 mm incision. The implanting technique has been developed by Dr D Dementiev. The lens is implanted in the eye with Dementiev titanium forceps under the protection of a viscoelastic. The implant is grasped with the forceps in such a way that the leading part of the lens corresponds to the end of the forceps. The lens is self-folding and can be inserted through a 3 mm incision. The pupil should be dilated at least 5 mm wide. The lens should be slightly folded with the spatula maneuvered through a side port incision in order to be pushed under the iris (Figs 16.2 and 16.3). It is extremely important not to cause pressure on the crystalline lens or to cause pressure on the zonula. When both haptics are placed under the iris the viscoelastics should be irrigated out and acetylcholine solution injected. An iridectomy should be performed preferably at 12 o’clock. At the end of surgery 1 mg of cefuroxime is injected in the anterior chamber. As anesthesia is used I prefer subtenon or just topical anesthesia if the patient is cooperative.

Figure 16.2: Patients with iris tissue attached to the crystalline lens. The iris strand was cut before introducing the PRL lens in the eye. This resulted in a small remnant of approximately 0.5 mm iris tissue on the crystalline lens

Figure 16.3: The same eye as in Figure 16.2 with a PRL lens floating in the posterior chamber. On the crystalline lens surface a small iris remnant is present under the PRL showing that there is a space between the two lenses

INDICATIONS

The indication for this PRLTM lens is mainly myopia higher than –8 and for patients younger than 45 years old of age. If there is a concomitant astigmatism this has to be treated by arcuate incisions or by LASIK or with another lens with toric design. The patients should not have other eye pathology and the anterior chamber depth should be more than 2.5 mm. It is extremely important to make a careful refraction both with and without cycloplegia. The PRL power is then selected through a power calculation table. For hyperopia the power selection is less exact, mostly due to the big difference between the manifest and the cycloplegic refraction. The lens has so far been used in more than 5000 eyes and the general feeling is that it gives a very good correction and the patients are very pleased.

TRIAL

An Eleven Centre European trial has been performed where I have been one of the participating surgeons. Among the 186 myopic patients who underwent implantation of the lens for myopia we have the twelve months results. The lenses were implanted in patients with a myopia of –3.5 to –30 D and the mean myopia was –13.3 D. The preoperative best corrected visual

acuity was 0.73 and the mean postoperative uncorrected visual acuity after 1 year was 0.74. The postoperative best corrected visual acuity improved to 0.94 and 80 percent of the patients gained at least one line of vision why 50 percent of the patients gained two or more lines. We found that almost 70 percent of the eyes are within ±0.5 D and 90 percent of the patients were within ±1 D of the intended refraction. The relatively low preoperative visual acuity of these patients is due to the fact that a number of patients included in the study had amblyopia or lower visual acuity due to retinal degenerations.

COMPLICATIONS

The most common immediate postoperative complication is a rise in the intraocular pressure due to remnants of viscoleastic. An increase of IOP to greater than 25 mmHg occurred in 5.5 percent during the early postoperative period. A transient corneal edema occurred in 27.6 percent of the eyes during the first postoperative day. With a careful surgical technique the endothelial cell loss should be very low and in the European trial the endothelial cell loss was averaging 6.3 percent after one year.

The most severe complications except for endophthalmitis, which did not occur in the study, are cataract or luxation of the PRL into the vitreous body. In the 186 eyes of the myopes in the European study one case of traumatic cataract and one case of luxation of the

PRL into the vitreous body occurred. Optical complications included glare in 13 percent and halos in 39 percent. Thirteen percent noticed a difficulty in driving at night. Most of these patients learned to disregard these optical phenomena over time.

RESULTS

The patients are generally extremely satisfied with the visual performance and much more satisfied than patients who have undergone corneal refractive surgery. One advantage with using a refractive lens is that the procedure is reversible although the disadvantage is the risk for damaging the crystalline lens. There is a risk for cataract development in about 2 percent and then a cataract extraction could be necessary to perform. The most severe complications have been luxation in the vitreous cavity which has been reported in 8 cases of the 5500 PRLs implanted. It is thus very important to fold the lens and not push it against the zonula fibre. If this is done on healthy eyes the risk should be extremely low for this complication. A special caution should be taken if a laser iridectomy has been performed preoperatively as this could weaken the zonula.

Postoperatively if there is a remaining astigmatism I general perform arcuate incision. If there is some remaining myopia and astigmatism I have in a few cases performed LASIK. Generally the patients are extremely satisfied with their visual performance.

H Burkhard Dick

Mana Tehrani (Germany)

INTRODUCTION

Purpose: To evaluate safety, efficacy, predictability, stability, complications and patient satisfaction after implantation of TPIOLs for the correction of myopia or hyperopia with astigmatism.

Methods: We conducted a prospective, randomized (selfcontrolled) clinical trial of thirty-one eyes (22 myopic, 9 hyperopic) of seventeen patients with high ametropia and astigmatism. After a minimum of at least six months, all eyes were examined by measuring corrected visual acuity, uncorrected visual acuity, refraction, astigmatism, endothelial cell count, intraocular pressure, slit-lamp biomicroscopy, and indirect ophthalmoscopy.

Results: Mean best spectacle-corrected visual acuity (BSCVA) was 20/30 and improved postoperatively to 20/25 in both groups. In the myopic group 78 percent (17/22) of eyes gained one or more lines compared to their preoperative BSCVA. In the hyperopic group 44 percent (4/9) of eyes gained one or more lines of BSCVA postoperatively. In 29 of 31 eyes (93.5%), the postoperative residual refraction was within ± 1 diopter of the targeted refraction. The mean endothelial cell loss at six months was 4.3 percent. The refractive effect was stable for all eyes at six months postoperative.

Conclusion: The implantation of the iris-claw PTIOL allows accurate refractive outcomes in eyes with high ametropia and astigmatism with one procedure.

Conservative options such as spectacles and contact lenses are the safest method for correcting ametropia with astigmatism. Unfortunately, some patients cannot

tolerate contact lenses, and spectacles can cause picture minimization and visual field limitations. Corneal reshaping procedures, such as relaxing incisions, laser in situ keratomileusis (LASIK), or photorefractive keratectomy (PRK), are currently popular. However, especially in cases of high refractive error, keratorefractive techniques can be associated with an increased risk of corneal ectasia, decreased visual quality, and poor predictability.1 In addition, the correction of astigmatism is limited.

A recent alternative is the implantation of a toric phakic intraocular lens (TPIOL) that enables intraocular correction of ametropia with astigmatism. In 1986, Worst and Fercher modified the existing iris-claw lens into a negative biconcave lens with a convex concave optic shape. Since then, it has been successfully implanted as the Worst myopia claw lens. Its name was changed to Artisan lens in 1998.1-3 The Artisan lens, also named Verisyse (Ophtec, Groningen, Netherlands, Advanced Medical Optics official distributor of Ophtec phakic IOLs in the United States) is manufactured with a spherical anterior surface and a toric posterior surface. Two opposed haptics enable fixation on the iris. In recent years the spherical iris-claw lens has been implanted with good results.1-7

This prospective study was designed to evaluate the clinical and refractive results of this new iris-supported TPIOL model for the correction of ametropia and astigmatism.

PATIENTS AND METHODS

Thirty-one eyes of seventeen patients who underwent surgery at the University Hospital, Department of Ophthalmology, Mainz, Germany, from February 2000 to September 2001, were included in this prospective study. Eyes were divided into group M, myopia (n =22) and group H, hyperopia (n = 9). Patient age ranged from 21 to 47 years in the myopic, and 32 to 49 years in the hyperopic group. Nine patients were female, eight male. All eyes were examined six months after surgery.

Patients older than 18 years, with stable refraction for at least 1 year and astigmatism greater than 1.50 D,

who also had an otherwise normal ophthalmologic examination, and unsatisfactory correction with spectacles or contact lenses for medical, professional, or personal requirements, were included. All patients were fully informed about the details and possible risks of the procedure. Written informed consent was obtained from all patients before surgery in accordance with the Declaration of Helsinki. The study was approved by the local Ethics Committee.

Exclusion criteria were anisometropia, anterior segment pathology, inadequate eyelid closure, endothelial cell count of less than 1800 cells/mm2, anterior chamber depth less than 3.0 mm, abnormal iris or pupil function, fixed pupil size greater than 4.5 mm, recurrent or chronic uveitis, any form of cataract, previous corneal or intraocular surgery, intraocular pressure (IOP) greater than 21 mmHg, glaucoma or family history of glaucoma, retinal detachment or family history of retinal detachment, preexisting macular degeneration or macular pathology, systemic diseases, chronic treatment with corticosteroids or any immuno-suppressive treatment or state, and pregnancy.

The toric phakic one-piece compression-molded TPIOL consists of Perspex CQ-UV polymethylmethacrylate with Tinuvin 326, a benzotriazole exhibiting effective UV filtration up to approximately 400 nm. The optic diameter is 5.0 mm and the overall length is 8.5 mm. Available TPIOL powers were from –3 D to –23.5 D for myopia, and +2 D to +12 D for hyperopia, with a cylindrical correction from 1.0 D to 7.0 D in 0.5 D steps.

The TPIOL is available in two models depending on the axis ofastigmatism. In eyes with a preoperative cylinder axis between 0° and 45° or between 135° and 180°, an IOL with a torus at 0° is recommended (Model A). In eyes with a preoperative cylinder axis between 45° and 135°, a torus at 90° is recommended (Model B). Both models can be enclavate in the required position.1

IOL calculations were based on the van-der-Heijde formula8 using the mean corneal curvature (K), the adjusted anterior chamber depth [ACD-0.8 mm (distance between IOL and crystalline lens)], and the patient’s

spherical equivalent at a vertex distance of 12 mm. All power calculations were performed by Ophtec BV (Groningen, Netherlands).

Preoperative preparation was the same as for typical cataract surgery but included miotic drops (pilocarpine 1 to 2 %) in place of mydriatics to prepare the iris for lens fixation. In all eyes, a superior sclerocorneal selfsealing 5.1 to 5.3 mm incision and two paracenteses were created. After insertion of a cohesive ophthalmic viscoelastic (Healon, Pharmacia) through the paracenteses to maintain a sufficient anterior chamber depth and protect endothelial cells, the iris-claw lens, with a 5.0 mm optic diameter, was enclavated onto the iris. The precise cylindrical axial orientation was ensured using marks on the limbus or using natural structures such as iris crypts or vessels.

Preand postoperative visits at one week, and one, three and six months included: determination of uncorrected visual acuity (UCVA), best-spectacle corrected visual acuity (BSCVA), keratometry and/or computerized corneal topography, manifest and cycloplegic refraction (45 minutes after two drops of 1 percent cyclopentolate) to calculate the spherical equivalent (SE), slit-lamp biomicroscopy to determine TPIOL position and axis, evaluation of any crystalline lens changes after mydriasis, applanation tonometry, evaluation of the central corneal endothelial cell count using contact specular microscopy, measurement of the anterior chamber depth (optical biometry), and indirect

ophthalmoscopy. We adopted the standardized format for reporting refractive surgery results described by Koch et al.9

Finally a questionnaire was given to each patient to evaluate subjective postoperative satisfaction. The scale was from 1 to 10, 1 for not satisfied and 10 for very satisfied.

Descriptive statistics, multivariate analysis, and correlation analysis were conducted with StatView for Macintosh (Release 4.51; Abacus Concepts, Berkeley, CA). Continuous variables were described with mean, standard variation, median, minimum, and maximum values. The paired Student t-test was used to evaluate the significance of the within-group difference. A p-value of less than 0.05 was considered significant.

RESULTS

Refraction

Preoperative mean spherical equivalent refraction was –9.14 ± 4.95 D in the myopic (A) and +3.82 ± 1.53 D in the hyperopic group. Mean astigmatism was –3.57 ± 1.12 D (min: –5.50 D, max: –1.75 D) in group M and –3.50 ± 0.76 D (min: –4.25 D, max: –2.00 D) in group H. Mean preoperative anterior chamber depth was 3.78 ± 0.29 mm in group M and 3.36 ± 0.3 mm in group H (Table 17.1).

The mean postoperative best spectacle corrected visual acuity for all eyes was 20/25 after six months. The overall refractive safety index of the procedure (ratio

Figure 17.1: Gains and losses of BSCVA in latest postoperative visit

of mean BSCVA postoperative/mean BSCVA preoperative) assessed at six months was 130 percent. In group M three eyes of 31(14%) lost one line, two (9%) eyes remained unchanged, eight eyes (37%) gained more than one line and nine eyes (40%) gained more than two lines. Sixty-eight percent of eyes (17/22) had gained one or more lines compared to the preoperative BSCVA. In group H no eye lost one line, five (56 %) eyes remained unchanged, three eyes (33%) gained more than one line and one (11%) gained more than two lines. 44 percent of eyes (4/9) had gained one or more lines compared to the preoperative BSCVA (Fig. 17.1).

Uncorrected visual acuity (UCVA) was 20/32 or better for all eyes after six months (31 eyes). All eyes had a postoperative improvement in UCVA compared with preoperative values (Fig. 17.2). In group M 18 eyes (83%) had an UCVA of 20/40, or better, 13 eyes (60%) of 20/32 or better. In group H 7 eyes (73%) had an UCVA of 20/40 or better, 6(62%) of 20/32 or better. The overall efficacy index (mean postoperative UCVA/ mean preoperative BSCVA) was 1.0.

The deviation of the achieved spherical equivalent correction from the calculated refractive spherical equivalent correction was calculated. After six months, 29 of 31 eyes (93.5%) were within ± 1 D of the desired refraction (Figs 17.3A and B).

The mean spherical equivalent after six months was –0.36 ± 0.41 D (min: –1.50 D, max: 0.00 D) in group M (n = 22) and –0.21 ± 0.36 D (min: –0.63 D, max:

Figure 17.2: Postoperative uncorrected visual acuity

Figures 17.3A and B: A. Predictability of achieved spherical equivalents in the myopic group. B. Predictability of achieved spherical equivalents in the hyperopic group

0.50 D) in group H (n = 9). The change in refraction (stability) was in mean –0.18 D in group M and –0.32 D in group H.

Astigmatic Correction and Rotational Stability

In group M the mean cylinder decreased from –3.57

± 1.12 D (min: –5.50 D, max: –1.75 D), preoperatively to –0.5 ± 0.5 D (min: –1.75 D, max: 0.00 D) at six month. In group H, the mean cylinder decreased from –3.50 ± 0.76 D (min: –4.00 D, max: –3.00 D) to – 0.56 ± 1.2 D (min: –2.0 D, max: +2.25 D). This represents a mean reduction in astigmatism of 3.07 D in group M and 3.06 D in group H (Figs 17.4 and 17.5). The mean difference between intended and achieved cylinder axis, determined at the last visit, was 3.5° ± 3° (min: 0°, max: 13°).

Endothelial Cell Loss and Intraocular Pressure

The mean preoperative endothelial cell count was 3221

± 405 cells/mm2 (min: 1870 cells/mm2, max: 3900 cells/ mm2). The mean endothelial cell loss was 1.7 percent after one week, 4.9 percent after one month, 3.7 percent after three months and 4.5 percent after six months compared to preoperative values (Fig. 17.6).

Figure 17.5: Double-angle-plot (Holladay) at 6 month postoperatively

Figure 17.4: Double angle plot (Holladay23) before surgery, showing the wide distribuation of cylinder. The double angle plot presents a polar plot of the preoperative spectacle plane refractive astigmatism at a vertex of 12 mm using the value of the plus cylinder for the magnitude and the axis of the astigmatism for the angle1

Figure 17.6: Endothelial cell loss in the postoperative follow-up

Mean preoperative intraocular pressure (IOP) was 14.7 ± 1.8 mmHg (min: 10 mmHg, max: 18 mmHg). Six months postoperatively the mean IOP was 14.3 ± 2.3 mmHg (min: 9 mmHg, max: 19 mmHg). After 1 year, the mean IOP was 13.8 ± 3.2 mmHg (min: 9 mmHg, max: 21 mmHg)(Fig. 17.7).

COMPLICATIONS

A transient corneal edema occurred in one eye that disappeared completely after one week. In seven eyes, iris pigment precipitates of varying intensity were observed on the optic of the TPIOL. Two eyes had an increased intraocular pressure immediately after surgery that normalized without the need for local therapy. In one