Ординатура / Офтальмология / Английские материалы / Phakic Intraocular Lenses_Hardten, Lindstrom, Davis_2004

Figure 13-6A. The Artisan lens for hyperopia (courtesy of Ophtec USA Inc).

3 years, 79.8% of eyes had a spherical equivalent within 1 D of the attempted correction. Twelve eyes had presented with myopia greater than -20 D with no IOLs of such power available. When these were excluded, 91.4% of eyes were within 1 D of attempted correction.

Landesz et al9 examined 78 eyes implanted with the Artisan lens, 10 of which received the 6.0-mm optic lens. Mean follow-up was 10 months. The preoperative spherical equivalent ranged from -6 to -28 D. A little over 67% of eyes were within 1 D of emmetropia. UCVA was 20/40 or better in 88.6% of eyes. Two eyes lost two lines of BSCVA, while most eyes had an improvement in BSCVA.

A group of 67 eyes implanted with the 5-mm optic Artisan lens and followed for 3 years was analyzed by Landesz et al10 Preoperative refraction ranged from -5.40 D to -28.0 D. A little over 67% of eyes had a postoperative spherical equivalent within 1 D of emmetropia. UCVA was 20/40 or better in 40.9% of eyes. Change in BSCVA showed an increase of one line or more in the majority of eyes. Three eyes lost two or more lines of BSCVA.

ARTISAN LENS FOR HYPEROPIA

An Artisan hyperopia lens was developed and first implanted in 1992 (Figure 13-6). The Phase III Interim Report of the FDA trial revealed data from 59 eyes from 38 subjects.11 All eyes received the 5-mm optic Artisan lens for hyperopia. The mean implant power was +7.18 D with a range of +4.0 D to +11.0 D. UCVA was 20/40 or better in 88.2% of eyes at 6 months and 82.4% of eyes at 2 years. At 6 months, 1 year, and 2 years, 100% of eyes had BSCVA of 20/40 or better

Surgery-related complications were observed, such as flare in 20.4% of eyes on postoperative day 1 but not at 3 months. Glare was reported by one patient at 1 week but resolved. No significant endothelial cell loss was seen at

Figure 13-6B. The Artisan lens for hyperopia (courtesy of Ophtec USA Inc).

3 years. Three patients experienced posterior synechiae. It was found that these eyes did not initially meet the inclusion criteria for the study due to peaked pupils.

Alio et al12 looked at 57 eyes of 32 patients implanted with the Artisan lens for hyperopia. Twenty-nine of the 57 eyes had primary hyperopia (mean spherical equivalent +6.06 1.26 D), while 28 eyes had secondary hyperopia induced or residual following a previous corneal refractive procedure (mean spherical equivalent +5.99 1.88 D). In the primary hyperopia group, the mean spherical equivalent postoperatively was +0.10 0.57 D. The mean UCVA improved to a mean of 20/40. No eye lost two or more lines of BSCVA. In the secondary hyperopia group, the mean spherical equivalent postoperatively was +.55 1.49 D. The mean UCVA improved to a mean of 20/50. One eye lost three lines of BSCVA, and one eye lost two lines. Of the six eyes that lost one line of BSCVA or more, three eyes were associated with an increase in irregular astigmatism and three eyes experienced acute iritis with pigment deposits on the lens surface. An acute anterior iritis was observed in three eyes, which were successfully treated with topical corticosteroids. Endothelial cell loss was measured as 6.8% at 6 months, and 9.4% at 1 year. Halos and glare were reported in four eyes (7%). Two eyes showed mild decentration less than 1 mm.

TORIC ARTISAN LENS

An Artisan toric phakic IOL was developed in 1999 for the correction of myopia or hyperopia with astigmatism (Figure 13-7). It is available in powers from -3 to -23.5 for myopia and from +2 to +12 for hyperopia, with cylindrical correction from 1.0 to 7.0 D.

Most surgeons prefer to position the Artisan lens horizontally; therefore, to accommodate this positioning technique, there are two models of toric Artisan lenses available. In model A (Figure 13-8), the torus axis runs through the claw at 0 degrees compared to the torus axis in model B, which is perpendicular to the line that runs through the claws.13 For eyes with a preoperative cylinder axis between 0 and 45 degrees or between 135 and 180 degrees, a toric lens with the axis at 0 (model A) is recommended. For eyes with a cylinder axis between 45 and 135 degrees, model B is recommended. Marking the enclavation sites on the iris with an argon laser before surgery or

marking the limbus at the site of the incisions to allow introduction of the enclavation forceps has been recommended.13

Figure 13-8. The Artisan Toric lens (model A) with torus axis running through the claw at 0 degrees (courtesy of Ophtec USA Inc).

Results

A European multicenter study was published with data on eyes implanted with the toric phakic Artisan IOL.13 Seventy eyes of 53 patients were studied in a prospective fashion. Two groups were analyzed: Group A with myopia (average preoperative spherical equivalent of -8.9 4.52 D) and Group B with hyperopia (average preoperative spherical equivalent of +3.25 1.98 D). At 6 months, UCVA was 20/40 or better in 88.6% of eyes. No eyes lost lines of BSCVA. Forty-six eyes (65.7%) gained one or more lines of BSCVA compared to preoperative BSCVA. In all eyes, the postoperative spherical equivalent at 6 months was within 1 D of attempted correction.

Complications

Two eyes required a secondary surgery. One eye had a wound leak, while the other required a repositioning of the lens because of a deviation of 15 degrees from the target axis. In one eye, pigment precipitates on the optic were seen. Four patients reported mild or moderate glare. Mean endothelial cell loss was 4.5% at 6 months.

COMBINATION OF LASER IN-SITU

KERATOMILEUSIS AND ARTISAN FOR

THE TREATMENT OF HIGH MYOPIA

One of the challenges of correcting high myopia with LASIK is that it is difficult to maintain a large optical zone when attempting to correct high myopia because of excessive ablation. The concept of adjustable refractive surgery combining Artisan lens implantation with LASIK was evaluated by Guell et al.14 In this technique, the lamellar cut for LASIK was made prior to implantation of the Artisan

lens to avoid any possible contact between the corneal endothelium and the anterior chamber during the microkeratome pass. A standard -15.00 D, 6-mm optic Artisan lens was used in all patients followed by LASIK with a 6.5- mm optical zone. LASIK was performed between 2 to 4 months after IOL implantation once all sutures had been removed and the cylinder power was stable for at least 4 weeks. Twenty-six eyes of 18 patients were enrolled, with a mean preoperative refractive error of -18.42 2.73 D, ranging from -16.0 to -23.0 Ds.

The mean postoperative spherical equivalent refraction before LASIK was -3.42 1.62 and after LASIK was -0.380.65 D at 12 months. Seventy-seven percent of eyes achieved UCVA of 20/40 or better at 1 and 2 years. All eyes were within 1 D of emmetropia at 2 years and 80% of eyes were within 0.5 D. No eyes lost two or more lines of BSCVA, and 72% of eyes gained one or more lines of BSCVA at 1 year. No statistically significant difference in endothelial cell counts was found throughout the followup period. There were a few flap complications, including one free cap, one traumatic flap dislocation, and one short flap. Only two patients reported visual disturbances at night.

LASER IN-SITU KERATOMILEUSIS

COMPARED TO THE

ARTISAN LENS FOR HIGH MYOPIA

Some investigators have compared the safety and efficacy of LASIK with Artisan lens implantation for the treatment of high myopia. Malecaze et al15 enrolled 25 patients with moderate high myopia ranging from -8 to -12 D in a prospective trial in which one eye received

142 Chapter 13

LASIK and the other received Artisan IOL implantation. All eyes that underwent Artisan lens placement received the 6-mm optic lens. The mean spherical equivalent at 1 year postoperatively was -0.74 0.67 D in the LASIK treated eyes and -0.95 0.45 D in the Artisan treated eyes. Sixty-four percent of the LASIK treated eyes and 60% of Artisan treated eyes were within 1 D of intended correction at 1 year. In the LASIK eyes, the mean cylinder power was corrected from +0.83 0.75 D to +0.42 0.55 D at 1 year. There was no correction of astigmatism in the Artisan treated eyes. At 1 year, 80% of the LASIK treated eyes and 60% of the Artisan treated eyes had UCVA of 20/40 or better. This difference was not statistically significant (p = .13). Three eyes treated with LASIK lost two or more lines of BSCVA, while no Artisan treated eyes lost two lines. As well, six Artisan cases had improvement of BSCVA, while only two LASIK cases had improvement. The endothelial cell loss was 0.42 11.95% for LASIK and 1.76 12.05% at 1 year, a difference that was not statistically significant. No significant difference was seen in reported halos and glare and in reported satisfaction level between the two groups. However, when patients were asked which eye they preferred, most patients showed a preference for the Artisan treated eye.

Another study comparing LASIK with Artisan was conducted by El Danasoury et al.16 Ninety-one eyes of 61 patients were prospectively randomized for either LASIK or an Artisan implant for the correction of myopia ranging from -9.00 to -19.50 D. In 18 patients, one eye received Artisan and one eye underwent LASIK. Between months 3 and 6, seven LASIK eyes and one Artisan eye underwent enhancement procedures. At 1 year, there was no statistically significant difference between the mean spherical equivalent of each group: -0.64 0.8 D in Artisan eyes and -0.87 0.8 D in LASIK eyes. A little over 65% of Artisan eyes and 58.5% of LASIK eyes were within 1 D of emmetropia. There was a statistically significant change in mean refractive cylinder power in the LASIK eyes (1.2 0.87) compared to the Artisan eyes (0.60 0.81). At 1 year, 88.4 % of Artisan eyes and 58.5% of LASIK eyes had UCVA of 20/40 or better. No Artisan eyes and five LASIK lost two or more lines of BSCVA. Seven Artisan eyes and one LASIK eye gained two or more lines of BSCVA. There was no significant difference in the mean endothelial cell loss in the two groups (0.7% 1.1 for the Artisan group and 0.3% 0.9 for the LASIK group). Fourteen percent of patients reported symptomatic night glare. One eye in the Artisan group who reported severe night glare had exchange of a 5-mm optic lens for a 6-mm optic lens and reported a reduction of the glare. Seven eyes treated with LASIK reported severe night glare.

The subgroup of 18 patients who had one eye treated with LASIK and the other with the Artisan lens complet-

ed questionnaires postoperatively with questions regarding satisfaction and preference. Thirteen of 18 (72.2%) patients preferred the Artisan procedure, and the reason given was the better quality of vision.

In conclusion, Artisan lens implantation has favorable results when compared to LASIK for high or moderately high myopia. No Artisan eyes lost two or more lines of BSCVA, and more Artisan eyes gained lines in BSCVA. Though there was no correction for astigmatism with the Artisan lens for myopia, the patients preferred the eye that had received the Artisan lens.

COMPLICATIONS

There are several potential complications with implantation of an Artisan lens, including effect on the corneal endothelium, anterior chamber inflammation, and crystalline lens changes.

The Phase III FDA trial data for the Artisan lens for myopia6 showed that in the early postoperative period, some eyes experienced complications related to surgically induced trauma (see Table 13-3). Anterior chamber flare was seen in 23.7% of eyes on postoperative day 1, but in only 5.1% at 2 weeks. Corneal edema was seen in 13.5% of eyes in the immediate postoperative period, but in only 1.4% of eyes at 2 weeks. One eye experienced pupillary block. No eyes at 6 months showed signs of iritis, secondary glaucoma, or iris atrophy. There was a mean change in endothelial cell counts of -1.11% at 12 months and -3.1% at 24 months. Thirty-five eyes were seen at 3 years with a mean change of +0.3%. Glare and halos were reported by 9.1% of patients at 12 months and were attributed by the authors to decentered lenses or pupils larger than the optic size in low light conditions.

The European Multicenter Trial7 showed endothelial cell loss of 4.8% at 6 months, 2.4% at 2 years, and 0.7% at 3 years. Patients reported halos more frequently in the very high myopia group (10%) compared to the moderate myopia group (7%). Five eyes (2%) underwent repositioning of a decentered lens, and eight eyes (3.2%) had a lens exchange performed.

Menezo et al8 reported glare symptoms in 4.25% of eyes and halos in 23.4% of eyes. Halos were twice as common in eyes receiving the biconcave model IOL, which is no longer used. Endothelial cell loss was measured as 5.8% at 6 months, 7.9% at 1 year, and 10.8% at 2 years. No retinal detachment or cataract was seen. Maloney et al2 reported no change in endothelial cell counts at 6 months compared to preoperative count. No eyes developed glaucoma, angle closure, or chronic inflammation.

Landesz et al10 reported mean endothelial cell loss of 5.5 % at 6 months, 7.2% at 1 year, and 9.1% at 2 years. One lens was recentered due to distorted images. One eye showed a severe inflammatory reaction in the anterior

chamber, which cleared with medical treatment. One eye developed a nuclear cataract in both eyes. Twenty-two percent of patients reported halos.

Landesz et al9 reported a gain in endothelial cell count postoperatively at each interval follow-up. The authors attributed this finding to the large variation in measuring cell density with the specular microscope used. Twelve percent of eyes experienced halos and glare. Three eyes were found to have anterior uveitis that resolved with treatment. Four eyes underwent replacement of lenses: two due to undercorrection and two due to halos with the 5-mm optic lens.

Perez-Santonja et al17 used a laser flare cell photometer to show that flare values were significantly higher for eyes implanted with the biconcave 5-mm lens. Halos were reported in 56% of eyes. They also showed a decentration greater than 0.5 mm in 43% of eyes. It is unclear how much decentration is necessary to be visually significant.

CONCLUSION

There are many advantages of Artisan lens implantation for high myopia. The lens is removable, and can be exchanged if needed. The optic of the lens has better pupil coverage than many eyes that receive LASIK treatment with less than ideal optical zones. The use of the 6-mm optic lens has reduced the incidence of glare compared to patients who received the 5-mm optic lens. However, the 6-mm lens is offered only up to -15.50 D; therefore, residual myopia will need to be addressed through subsequent corneal refractive procedures.16 Though surgeons must currently make a 6.0- to 6.5-mm wound for insertion of the lens, in the future a foldable Artisan lens, Artiflex, will be available that will allow a smaller surgical wound for lens placement.

Patients tend to prefer the quality of the vision that Artisan implantation affords compared to LASIK and more eyes gain BSCVA compared to LASIK.15,16 Randomized trials have shown predictability, safety, stability, and accuracy in the correction of myopia by Artisan lens implantation. Concerns of postoperative loss of endothelial cell counts and increased incidence of cataract will need to be addressed in further long-term examination of the Artisan lens.

REFERENCES

1.Seiler T, Koufala K, Richter G. Iatrogenic keratectasia after laser in situ keratomileusis. J Refract Surg. 1998;14:312-317.

2.Maloney RK, Nguyen LH, John ME. Artisan phakic intraocular lens for myopia; short term results of a prospective multicenter study. Ophthalmology. 2002;109(9):1631-1641.

The Artisan Phakic Intraocular Lens 143

3. Pop M, Mansour M, Payette Y. Ultrasound biomicroscopy of the iris-claw phakic intraocular lens for high myopia. J Refract Surg. 1999;15(6):632-635.

4.Pop M, Payette Y, Mansour M. Ultrasound biomicroscopy of the Artisan phakic intraocular lens in hyperopic eyes.

J Cataract Refract Surg. 2002;28:1799-1803.

5.Hardten DR. Phakic iris-claw artisan intraocular lens for correction of high myopia and hyperopia. Int Ophthalmol Clin. 2000;40(3):209-221.

6.2002 Artisan Myopia Lens Annual Progress Report. Phase III Interim Report. Groningen, Netherlands: Ophtec; 2002.

7.Budo C, Hessloehl JC, Isak M, et al. Multicenter study of the Artisan phakic intraocular lens. J Cataract Refract Surg. 2000;26:1163-1171.

8.Menezo JL, Avino JA, Cisneros A, et al. Iris-claw phakic intraocular lens for high myopia. J Refract Surg. 1997;13: 545-555.

9.Landesz M, van Rij G, Luyten G. Iris-claw phakic intraocular lens for high myopia. J Refract Surg. 2001;17(6):634640.

10.Landesz M, Worst JG, van Rij G. Long-term results of correction of high myopia with an iris-claw phakic intraocular lens. J Refract Surg. 2002;16(3):310-316.

11.2002 Artisan Hyperopia Lens Annual Progress Report. Phase III Interim Report. Groningen, Netherlands: Ophtec; 2002.

12.Alio JL, Mulet ME, Shalaby AM. Artisan phakic iris-claw intraocular lens for high primary and secondary hyperopia. J Refract Surg. 2002;18(6):697-707.

13.Dick HB, Alio J, Bianchetti M, et al. Toric phakic intraocular lens: European multicenter study. Ophthalmology. 2002;110(1):150-162.

14.Guell JL, Vazquez M, Gris O. Adjustable refractive surgery: 6-mm Artisan lens plus laser in situ keratomileusis for the correction of high myopia. Ophthalmology. 2001;108(5): 945-951.

15.Malecaze FJ, Hulin H, Bierer P, et al. A randomized paired eye comparison of two techniques for treating moderately high myopia: LASIK and Artisan phakic lens. Ophthalmology. 2002;109(9):1623-1630.

16.El Danasoury MA, El Maghraby A, Gamali TO. Comparison of iris-fixed Artisan lens implantation with excimer laser in situ keratomileusis in correcting myopia between -9.00 and -19.50 Ds. Ophthalmology. 2002;109(5):955-964.

17.Perez-Santonja JJ, Bueno JL, Zato MA. Surgical correction of high myopia in phakic eyes with Worst-Fechner myopia intraocular lenses. J Refract Surg. 1997;13:268-284.

18.Fechner PU, Haubitz I, Wichmann W, Wulff K. Worst-

Fechner biconcave minus power phakic iris-claw lens. J Refract Surg. 1999;15:93-105.

The Phakic Refractive Lens (PRL) has been in development since 1987.1 It was designed and initially manufactured by Medennium, Inc (Irvine, Calif) and distributed by CIBA Vision (Duluth, Ga). In February 2003, Medennium, Inc transferred full ownership of the PRL technology to CIBA Vision. The PRL is currently going through Phase III clinical trials for the US Food and Drug Administration (FDA).

The PRL is a plate-haptic style posterior chamber phakic intraocular lens (IOL). It is made of a medical-grade high-index silicone that is soft, elastic, and hydrophobic. The refractive index is 1.46. The material, one-piece design, and manufacturing process are all proprietary (Figure 14-1).

The lens is designed to float in the posterior chamber (Figure 14-2). The footplates are not designed to support the lens by putting pressure on the zonules or ciliary sulcus in a way that causes the optic to vault over the crystalline lens. Rather, this free-floating lens stays in position by being gently pushed against the posterior surface of the iris by hydrostatic forces. In this way, a layer of fluid is always maintained between the PRL and the crystalline lens. Pupillary block is avoided by the placement of two peripheral iridotomies or iridectomies. The lens is selfcentering by the action of the iris sphincter on the peripheral ridge of the optic, which is molded onto the anterior surface of the lens.

Because the PRL floats in the posterior chamber and the footplates are not anchored in the sulcus, it does not have to be sized as carefully as other lenses. Currently, only two sizes exist: one for myopic and one for hyperopic powered lenses. However, because the lens is not anchored, its

position is probably not as stable as other posterior chamber phakic IOLs that “vault” over the crystalline lens. The PRL has been reported to rotate over time. For this reason, it is possible that this particular lens will not lend itself to a toric design.

Two models of PRL are being implanted: one for myopes and one for hyperopes. The myopic PRL is 11.3 mm in length and 6.0 mm in width. The thickness of the lens is dependent upon the power, with a maximum thickness of 0.6 mm. The lens power range is -3 diopters

(D) to -20 D in half-diopter steps, which allows for correction of myopia up to -23.0 D. The optic diameter ranges from 4.5 mm to 5.0 mm depending on the power. An older myopic model (PRL 100) had an overall length of 10.8 mm. This model has been discontinued because of problems related to decentration.1

The hyperopic PRL is 10.6 mm in diameter. The range of lens power is +3 D to +15 D in half-diopter steps. Using this lens, hyperopia of up to +11.0 can be corrected. The optic diameter is 4.5 mm for all hyperopic PRL lenses.

Lens power calculation is based on the Russian method of converting to the corneal plane from a vertex distance of 12.0 mm. The PRL does not come in a toric design, and, therefore, cannot be used to treat astigmatism. In patients with astigmatism, the spherical equivalent is used in determining the power of the PRL to be implanted.

PREOPERATIVE CONSIDERATIONS

The range of correction of the PRL is from -23.0 D to +11 D. Rotation is common because there is no fixation of

Figure 14-1. Photograph of the CIBA Vision PRL. Note the curved plate haptic design. The lens is made from a proprietary soft, elastic, hydrophobic high-index silicone polymer.

Figure 14-2. Slit lamp photograph of the PRL properly positioned. The long axis of the lens is oriented horizontally following implantation through a temporal incision. Note that the 4.5-mm optic is molded onto the anterior surface of the 6.0-mm wide haptic of this myopic PRL.

this lens, making a toric version of this lens untenable. Patients with significant astigmatism will, therefore, not benefit as much as those without astigmatism if PRL insertion is performed as a sole procedure. Hoyos et al1 described success in alleviating high amounts of toric refractive error by pairing PRL implantation with astigmatic laser in-situ keratomileusis (LASIK).

Aside from refractive error, eyes undergoing implantation of PRL should have no pathology. As with any patient undergoing an elective refractive procedure, most clinicians agree that surgery should not be recommended on patients in whom the best-corrected visual acuity of the fellow eye is decreased below 20/40 or so. It is recommended that patients, especially high myopes, should undergo a rigorous peripheral retinal examination, including scleral depression, prior to implantation of the lens. Any suspicious retinal lesions should be treated with photocoagulation or cryotherapy prior to consideration of the PRL procedure.

Patients should not have a history of glaucoma or uveitis. They should not have a history of cataract, as there is concern that any phakic IOL may lead to increased opacification of the crystalline lens. In addition, patients should not have significant iris abnormalities, such as aniridia, correctropia, or angle recession.

Corneal thickness and topography have no bearing on either safety or tolerance of the PRL. In fact, phakic IOLs such as the PRL are likely the safer choice for patients with thin corneas or suspicious topography who desire refractive surgery. There is a concern that these patients have a higher likelihood of developing corneal ectasia following LASIK.2 Therefore, it may be safer to do surgery that spares the cornea in patients with thin corneas or topography consistent with forme fruste keratoconus.

Because of technical difficulties associated with implantation of all phakic IOLs, it is safer to implant the PRL in patients with greater anterior chamber depths. Most patients receiving a PRL are high myopes with increased axial lengths; therefore, the majority have anterior chamber depths greater than average. However, high hyperopes will often have shorter than average eyes and shallower than normal anterior chambers. Great care must be taken in these patients when inserting a PRL to ensure that damage to either the crystalline lens or corneal endothelium occurs. In order to be enrolled in the FDA Phase III trial, patients had to have an anterior chamber depth of at least 3.0 mm.

There is debate over the weight that pupil size should be given when considering implantation of the PRL. The optic diameter for the myopic PRL ranges from 4.5 to 5.0 mm, and for the hyperopic PRL, it is 4.5 mm. The overwhelming majority of articles evaluating pupil size in refractive surgery patients have looked only at cohorts of patients undergoing LASIK or photorefractive keratectomy (PRK).3 Because of the nature of corneorefractive technology, one would expect these results to be different from those seen with phakic IOLs.

It is conceivable that patients with high refractive errors, as a group, will have better results with phakic IOLs than LASIK, and it is this group for which the PRL will initially be recommended. Many practitioners have stopped performing LASIK for hyperopes with more than 4 D of hyperopia because of concerns with regression and postoperative quality of vision. Highly myopic corrections carry the increased risk of both ectasia secondary to excessive corneal thinning,2 and decreased quality of vision from increased spherical aberration and abnormally flat

postoperative keratometry. For these reasons, it is likely that the risk of intraocular surgery will be less than that of corneal laser refractive procedures for patients with significantly high refractive errors.

HISTORY

The PRL has been in development since 1987. In 2000, Dementiev et al presented their results with this lens in Agarwal’s Refractive Surgery.4 They specifically demonstrated their good results in implanting the PRL in Russia and Italy over a 10-year period.

In 2002, Hoyos and coworkers reported their results implanting the PRL in Spain between 1997 and 2000.1 Two surgeons implanted PRL in a total of 31 eyes of 17 patients. Seventeen eyes were myopic and 14 were hyperopic. All patients either had severe refractive errors (greater than -15.00 or +5.00) or had thin corneas. Minimal anterior chamber depth for inclusion was set at 2.8 mm.

Six eyes (two myopic and four hyperopic) underwent additional, planned LASIK because of greater than 2 D of preoperative cylinder. In these patients, the corneal flap was created 2 weeks prior to PRL implantation. The flap was lifted and the laser ablation was performed 1 to 2 months after implantation of the PRL.

All hyperopic eyes received the same model lens (PRL 200). This model is the one described above and has an overall length of 10.6 mm and an optic diameter of 4.5 mm. Some myopic patients received the PRL 100 model, which has an overall length of 10.8 mm, while others received the PRL 101 model, which has an overall length of 11.3 mm. Three eyes that received the PRL 100 model lens developed visually significant decentration diagnosed postoperatively. All three had the PRL 100 exchanged for PRL 101 and have done well. Because of this, the PRL 100 model is no longer available, and all myopic patients receive a PRL with an 11.3 mm overall length.

Refractive error improved considerably in this group of patients. Using log MAR analysis, the mean preoperative best-corrected visual acuity was 20/32. The mean postoperative uncorrected visual acuity was 20/39. A total of 12 eyes gained at least one line of visual acuity, and one hyperopic eye lost one line of best-corrected visual acuity. In the myopic group, 53% of eyes were within 0.5 D and 82% were within 1 D of the desired refraction. Of the hyperopes, 50% were within 0.5 D, and 79% were within 1 D of emmetropia. Of the six patients who had LASIK following PRL implantation, four were plano, one had a spherical equivalent of -0.50, and the sixth had a spherical equivalent of -0.75.

Complications were few and manageable. Two patients in the hyperopic group developed pupillary block. One of these occurred in the immediate postoperative period and

CIBA Vision Phakic Refractive Lens 147

was felt to be a result of an incomplete iridectomy. The second occurred 1.5 years after PRL implantation. The PRL had rotated 90 degrees and was positioned to block the single iridectomy. The pupillary block resolved after two peripheral iridotomies were placed using a neodymi- um:yttrium-aluminum-garnet (Nd:YAG) laser. One hyperopic eye developed pigment dispersion without evidence of elevated intraocular pressure.

One myopic patient developed steroid-induced elevated intraocular pressure that subsided after discontinuation of topical corticosteroids. One eye developed a small anterior subcapsular peripheral opacity in the crystalline lens that was felt to be secondary to lens touch with the insertion forceps during surgery. This opacity did not progress during the ensuing 2 years. A total of four patients reported an increase in halos and glare despite well-centered lenses.

A Phase II US FDA trial evaluated 100 myopic PRLs implanted by four surgeons. These data have not been published in the peer-reviewed literature and will not be discussed in detail here. However, results were similar to those demonstrated by Hoyos and coworkers in their work in Spain as described above.1 The Phase III US FDA trial for this lens is currently underway.

SURGICAL TECHNIQUE

The PRL is made of a soft, foldable, silicone material that can be implanted through a self-sealing clear corneal incision. Although the plate haptic shape will be familiar to many cataract/IOL surgeons, the material is much softer and more pliable than that of standard silicone IOLs. When handling this lens, the surgeon is reminded more of a thin, disposable, soft contact lens than of a silicone IOL.

Two peripheral iridectomies (PIs) must be performed four clock hours apart. In patients in the Spanish study described above, only one iridectomy was made. It was felt that the late angle closure that developed in that study would not have occurred if two PIs had been created instead of one. For this reason, it is recommended that all patients receive two PIs. The PIs are positioned at the 10:00 and 2:00 positions. In this way, if the PRL rotates so as to block one of the PIs, the other one will still be patent.

Some surgeons prefer to make these PIs using a Nd:YAG laser. In these cases, Nd:YAG peripheral iridotomy should be performed at least 1 to 2 weeks prior to the PRL implantation procedure. Other surgeons prefer to accomplish this through a surgical peripheral iridectomy.5 In these cases, PIs should be made during the PRL implantation procedure.

Implantation of the PRL should be performed under retrobulbar anesthesia. Care must be taken in performing retrobulbar blocks in high myopes, as many of these patients will have axial lengths of 30 mm or more and are

Figure 14-3. Ultrasound of the PRL positioned in the posterior chamber. Note that that footplates are not anchored in the ciliary sulcus. The lens is gently pushed anteriorly by the natural movement of aqueous humor within the eye. The lens optic is molded onto the anterior surface of the lens and is centered in the pupil by natural action of the iris sphincter.

more susceptible to posterior scleral injury from the retrobulbar needle. However, because retrobulbar anesthesia provides better anesthesia, amaurosis, and akinesia, it is felt that the benefit of retrobulbar anesthesia overrides the increased risk.

The patient is dilated per routine cataract surgery protocol. After the placement of the retrobulbar block, a honan balloon is applied at 30 mmHg, and the patient is brought to an operating room equipped for intraocular surgery. Standard phacoemulsification and a pseudophakic IOL should be available in the rare situation that trauma to the crystalline lens during PRL implantation necessitates emergent cataract extraction and intraocular lens implantation.

The eye is prepped and draped using the usual sterile fashion for intraocular surgery. A standard 3.0- to 3.5-mm clear corneal cataract incision is created with a diamond or metal knife, whichever the surgeon prefers. One millimeter paracentesis port incisions are made three clock hours to the left and right of the temporal incision. The anterior chamber is filled with a mildly cohesive viscoelastic, such as Biolon (Bio-Technology General Corp, East Brunswick, NJ).

The PRL is then inserted through the temporal incision (Figure 14-3). A special injector has been developed for this purpose (Figure 14-4). However, as of the writing of this text, the injector has not been approved for use in the FDA Phase III trial. Patients enrolled in the FDA Phase II trial and those reported by Hoyos and coworkers1 had implantation of the PRL with Dementiev forceps (Rumex International, Miami, Fla). These forceps open in an anteroposterior (vertical) fashion and are designed to grasp the haptic while avoiding the optic of the PRL. It is also designed to avoid both the crystalline lens and corneal epithelium upon opening. Most surgeons agree that safely and effectively inserting the PRL into the anterior chamber with forceps is the most technically challenging part of the procedure. The injector should make this aspect of the surgery significantly easier.

Once the PRL is placed into the anterior chamber, it is important for the surgeon to ensure that it is not inverted.

Figure 14-4. The PRL injector.

Because the optic is molded onto the anterior surface of the lens, the surgeon merely has to feel for its edge with a spatula to ensure that the lens is positioned appropriately. The four corners of the haptic are then merely tucked under the iris with a Dementiev PRL spatula (Rumex International, Miami, Fla) or similar instrument. Great care must be taken to ensure that neither the crystalline lens nor the corneal endothelium is damaged during surgical manipulation.

Once all four corners of the plate haptic are tucked under the iris, the cohesive viscoelastic is exchanged with Miochol (CIBA Vision, Duluth, Ga), which is instilled through a blunt-tipped cannula. Mechanical irrigationaspiration normally does not have to be performed. As the pupil comes down, the surgeon must ensure that the haptics stay posterior to the iris and the optic is centered in the pupil.

The wounds are tested for water-tightness and can be hydrated or sutured if any are found to leak. Topical antibiotic and corticosteroid are placed on the cornea, and the patient is given oral acetazolamide 250 mg immediately postoperatively. A fox shield is taped over the eye for the first day. The patient takes a second oral acetazolamide 250 mg at bedtime and begins topical antibiotic and corticosteroid four times daily on the first postoperative day. The patient is typically examined at postoperative days 1, 3, and 7, then postoperative months 1, 3, 6, and 12.

SUMMARY

The CIBA Vision PRL is proving itself a safe and effective alternative to laser vision correction. It is especially beneficial for patients with high spherical refractive errors or those who are not suitable candidates for keratorefractive procedures. Surgeons familiar with techniques of cataract extraction and posterior chamber lens implantation will find most techniques associated with implantation of this lens familiar. The fact that the lens floats in the posterior chamber makes it easier to size and will possibly lead to less cases of IOL-induced lens opacification than other posterior chamber phakic IOLs. However, this aspect of the lens will hinder the likelihood that a toric version of this lens will be developed.

As of the writing of this text, the PRL is going through US FDA Phase III trials. It has been used in Italy, Spain, and Russia with significant safety and efficacy.

REFERENCES

1.Hoyos JE, Dementiev DD, Cigales M. Phakic refractive lens experience in Spain. J Cataract Refract Surg.

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2.Randleman JB, Russell B, Ward MA. Risk factors and prognosis for corneal ectasia after LASIK. Ophthalmology. 2003;110(2):267-275.

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3.Haw WW, Manche EE. Effect of preoperative pupil measurements on glare, halos, and visual function after photoastigmatic refractive keratectomy. J Cataract Refract Surg. 2001;27(6):907-916.

4.Dementiev DD, Hoffer KJ, Sborgia G, et al. Phakic refractive lens for correction of myopia and hyperopia. In: Agarwal S, Agarwal A, Pallikaris IG, et al, eds. Refractive Surgery. New Delhi: Jaypee Brothers; 2000:440-461.

5.Hoffer KJ. Pigment vacuum iridectomy for phakic refractive lens implantation. J Cataract Refract Surg. 2001;27(8):11661168.