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

160 Chapter 15

a good postoperative vision. If the patient is too demanding and wishes the same vision after surgery, it is necessary to persuade him or her against this sort of device.

To conclude, this first series of phakic implants to correct presbyopia shows that the technique is effective and that it is reversible because the implant can be removed if an error has been made or if the patient is not satisfied. In the future, it can be hoped that optical engineering will be able to produce better quality optics and that we can perhaps adjust or exchange the implants used today. In some cases, unilateral correction was well tolerated if the dominant eye of the emmetropic patient is operated on. With an ametropic patient, it is necessary to treat the anisometropia by operating on the second eye using either a conventional refractive surgery technique or with a presbyopic implant adapted to his or her refraction.

REFERENCES

1.Baïkoff G, Arne JL, Bokobza Y, et al. Angle-fixated anterior chamber phakic intraocular lens for myopia of -7 to -19 diopters. J Refract Surg. 1998;14(3):282-293.

2.Baïkoff G. Phakic anterior chamber intraocular lenses. Int Ophthalmol Clin. 1991;7:277-281.

3.Mimouni F, Colin J, Koffi V, Bonnet P. Damage to the corneal endothelium from anterior chamber intraocular lenses in phakic myopic eyes. Refract Corneal Surg. 1991; 7:277-281.

4.Saragoussi JJ, Cotinat J, Renard G, Savoldelli M, Abenhaim A, Pouliquen Y. Damage to the corneal endothelium by minus power anterior chamber intraocular lenses. Refract Corneal Surg. 1991;7:282-285.

5.Baïkoff G, Colin J. Intraocular lenses in phakic patients.

Ophthalmol Clin North Am. 1992;5:789-795.

6.Werblin TP. The long-term endothelial cell loss following phacoemulsification. Refract Corneal Surgery. 1993;9:2935.

7.Baïkoff G, Samaha A. Phakic intraocular lenses. In: Azar D, ed. Refractive Surgery. Stamford, Conn: Appleton & Lange; 1997:545-560.

8.Baïkoff G. Refractive phakic intraocular lenses. In: Elander R, Rich L, Robin J, et al, eds. Principles & Practice of Refractive Surgery. Philadelphia, Pa: WB Saunders & Company; 1997:435-447.

9.Baïkoff G. Phakic myopic intraocular lenses. In: Serdarevic O, ed. Refractive Surgery—Current Techniques & Management. New York, NY: Igaku-Shoin; 1997:165-173.

10.Baïkoff G, David J. Phakic intraocular lenses. In: Azar D, ed.

Intraocular Lenses in Cataract & Refractive Surgery. Philadelphia, Pa: WB Saunders; 2001:245-255.

11.Baïkoff G. Phakic anterior chamber lenses. In: Gimbel H, ed. Refractive Surgery: A Manual of Principles and Practice.

Thorofare, NJ: SLACK Incorporated; 2000:218-229.

This publication was supported in part by an unrestricted research grant from Research to Prevent Blindness, New York, NY.

INTRODUCTION

The Phakic 6H2 (Ophthalmic Innovations International, Ontario, Canada) is the most recent phakic intraocular lens (IOL) designed for the treatment of moderate to high myopia. The Phakic 6H2 lens has evolved from the anterior chamber lenses pioneered by Strampelli,1 Barraquer,2,3 and Choyce4-7 for the treatment of aphakic refractive error, and further refined by the studies of Fechner,8,9 Praeger,10 Baïkoff,11-14 and Kelman1 for the treatment of phakic refractive error.

The evolution of phakic myopic IOL design over the last several decades has led to the unique Phakic 6H2 lens. The unique features of the Phakic 6H2 lens include a large 6.0- mm optic diameter; optic edge thinning to increase corneal clearance; a forward convex anterior lens face that has an antireflective coating; and advanced footplate and angular support features that minimize iris capture, iris irritation, and compression of the anterior chamber angle.15 The lenses are also coated with heparin to reduce inflammation.

In this chapter, we report the initial experience with the Phakic 6H2 lens in the United States. These cases are part of the ongoing US Food and Drug Administration (FDA) clinical trial that was initiated in 2001 to test the safety and efficacy of this lens for the treatment of myopia. This multicenter trial was conducted at four clinical sites and includes 6-month data from 28 patients.

PATIENTS AND METHODS

Patients were enrolled at four clinical sites according to a prospective protocol. The multicenter trial was developed utilizing the guidelines recommended by US FDA for the investigation of new anterior chamber IOL implants. All investigational sites obtained Institutional Review Board (IRB) approval for the study, and all patients gave informed consent. The investigators for this initial series of patients included Jay McDonald, MD (Fayetteville, Alaska); Daniel Tran, MD (Irvine, Calif); Tom Clinch, MD (Washington, DC); and David J. Schanzlin, MD (San Diego, Calif). The aim of the study was to show that correction of myopia (-4.0 diopters [D] to -20 D with up to 3.0 D of astigmatism) in human phakic eyes with the Phakic 6H2 heparinized anterior chamber IOL is safe and effective.

INCLUSION CRITERIA

To be enrolled in the study, subjects had to be adults between the ages of 21 to 55 years old, with myopia ranging from -4 to -20 D and less than 3 D of astigmatism. A stable correction (within 0.5 D by mean refractive spherical equivalent [MRSE]) was needed for at least 12 months prior to surgery. Soft contact lens wearers stopped wearing lenses 2 to 3 days prior to initial refraction, while hard or gas permeable lens wearers stopped at least 2 weeks prior to refraction. The spherical manifest and spherical cycloplegic refractions differed by no more than 0.75 D. Subjects needed to have two normal, healthy eyes with best spectacle-corrected vision of 20/40 or better. The

164 Chapter 16

patient’s anterior chamber depth had to be sufficient to accommodate the IOL, which in general meant that the anterior chamber depth needed to be greater than 2.9 mm. The patient’s white-to-white limbal dimensions needed to be between 11.0 and 13.0 mm. Patients could not have a history of previous intraocular surgical procedures. Patients between the ages of 21 and 45 had to have central endothelial cell count densities of at least 2500 cells/mm2, while patients over 45 had had to have a minimum central endothelial cell count density of 2000 cells/mm2. All patients had to agree to participate in the study and sign the IRB-approved Phakic 6H2 informed consent form.

EXCLUSION CRITERIA

Patients could not have prior intraocular or corneal surgery in the study eye. Patients with retinal vascular disease, hypercoagulability, autoimmune disease, connective tissue disease, diabetes, or an immunocompromised state were also excluded. Pregnant or nursing women were excluded from the study. Patients using ocular medications other than artificial tears or patients using systemic medications with known ocular side effects were also excluded from entry into the study.

DETERMINATION OF

ANTERIOR CHAMBER LENS POWER

The Phakic 6H2 lens power was calculated using the formula reported by Holladay.16 The formula is for determination of intraocular refractive implant power equivalent to the patient’s spectacle correction. The calculation for emmetropia can be altered to achieve any postoperative refraction. A series of tables that assist in these calculations may be obtained from the lens manufacturer.15

Definition of Variables:

Diol = Refractive power of IOL (D)

b = Distance between IOL and cornea (mm) Dc = Refractive power of cornea (D)

a = Distance between cornea and spectacle lens (mm) Ds = Refractive power of spectacle (D)

SURGICAL PROCEDURE

the usual sterile manner for ocular surgery and a lid speculum was introduced. A 7-mm corneal incision site was measured with a caliper and marked. Most cases had a clear corneal temporal incision. A paracentesis port was created 90 degrees from the incision site. Miochol was injected to bring down the pupil, and a small amount of viscoelastic was injected to maintain a stable anterior chamber throughout the surgical procedure. Care was taken not to overfill the anterior chamber nor to inject viscoelastic behind the iris. A self-sealing 7-mm corneal incision was made 0.5 mm inside the limbal margin. A 7-mm lens glide was then introduced with care to avoid contact between the lens glide, iris, endothelium, and crystalline lens. The lens was then introduced into the anterior chamber, using the lens glide as the path for insertion until the full optic was inside the anterior chamber and only the trailing haptic protruded from the incision. Then, the lens glide was gently withdrawn from the anterior chamber using viscoelastic to maintain the anterior chamber. The trailing haptic was then positioned into the angle beneath the corneal shelf using a tapered “pusher.” If an iris tuck was suspected, the angle was inspected using a Thorpe gonioprism (Ocular Instruments Inc, Bellevue, Wash). The incision site was closed with either a 10-0 nylon continuous or interrupted suture(s), and the suture knots were buried. Finally, continuous irrigation was applied to remove the viscoelastic. An antibiotic-steroid drop was applied to the eye at the close of the procedure, and then the speculum was removed. A clear shield was placed over the eye and was worn at bedtime for 1 week.15

POSTOPERATIVE PROTOCOL

Patients were examined on day 1, day 7, day 14, month 1, month 3, month 6, month 12, and month 24 according to the protocol (Figures 16-1 and 16-2). At each visit, an eye examination and visual testing were performed. Topical corticosteroid and antibiotic drops were continued for the first postoperative week. The intraocular pressure was monitored closely, and significant rises in pressure were treated with ocular antihypertensive agents. The nylon sutures were removed 2 to 6 weeks postoperatively if they induced postoperative astigmatism.

RESULTS

Demographics

One week prior to surgery, one or two laser iridotomies were performed. Preoperative measures also included administration of 4% pilocarpine drops to the operative eye 30 and 15 minutes prior to surgery. Topical anesthesia was the preferred method, but in select cases a peribulbar injection was used. Patients were prepped and draped in

Twenty-eight subjects were enrolled at all four sites as of December 2002, with 21 (75%) female and 7 (25%) male. The majority of patients were Caucasian (67.9%). The right and left eyes were operated on with equal frequency. The age range was 24 to 55 years (mean = 39.3 years) (Table 16-1).

Visual Acuity Outcomes

At 1 month, 66.7% of patients (16/24) had an uncorrected visual acuity (UCVA) of 20/40 or better. At month 3, 82% of patients maintained 20/40 or better (18/22). At the 6-month visit, 87.5% (14/16) maintained 20/40 or better unaided visual acuity. This is above the specified efficacy endpoint of 85% for postoperative UCVA for this study. At month 1, 12.5% (3/24) of patients were at 20/20. At month 3, 36.4% (6/22) of patients were at 20/20, while at month 6, 18.8% were at 20/20 (3/16) (Table 16-2).

At month 1, 37.5% of patients had a MRSE 0.50 D that increased to 59.1% (13/22) at month 3 and finally to 75.0% (12/16) at month 6. Overall, 93.8% of patients (15/16) had a MRSE -1 D at month 6 (see Table 16-2). These results are also above the specified efficacy endpoint for this criteria (75% of patients have MRSE 1.00 D of intended correction and 50% of patients have MRSE0.5 D of intended correction) (see Table 16-2).

Maintenance or Loss of Best Spectacle-Corrected Visual Acuity

In terms of safety, no patient lost >2 lines of best spec- tacle-corrected visual acuity (BSCVA). In addition, no patient had BSCVA worse than 20/40 or had >2 D of increased cylinder (see Table 16-2). Safety endpoints specified in this study for loss of BSCVA <2 lines should be less than 5%, BSCVA worse than 20/40 was not to exceed 1%, and increased cylinder of >2 D should be less than 1%.

Best-corrected visual acuity (BCVA) for distance showed 41.7% (10/24) of patients at month 1 to have 20/20 acuity. Fifty-nine percent (13/22) of patients at month 3 had 20/20 acuity, and finally 50% (8/16) maintained 20/20 visual acuity (Table 16-3).

One patient exhibited raised intraocular pressure immediately postoperatively that was not seen at the 3 or 6 month visit. No other complications or adverse reactions were reported in any other study patient.

DISCUSSION

The history of phakic IOLs for the correction of myopia goes back 50 years. In 1953, Strampelli1 implanted the first anterior chamber IOL in an aphakic eye to correct myopia. As early as 1959, Barraquer2,3,17 reported on 239 implantations, and Choyce4-7,18 reported his experience with 12 cases in 1964. Several complications were reported in these early series, including corneal decompensation. In these early reports, approximately 60% of the lenses were explanted.19-22

In 1983 to 1984, Kelman introduced his anterior chamber IOL implant design. Although introduced for the correction of aphakic refractive errors, the design was soon adapted for myopic correction.1,23 In 1986, Dvali1 reported his experience with the phakic anterior chamber IOL to correct myopia. Later that year Fechner,8,9 Baïkoff,11-14 and Fyodorov1 became interested in IOLs in the phakic eye. The ZB implant (Bausch & Lomb Surgical, Rochester, NY) was born from their work and is considered one of the first modern refractive implants with angular support.

In 1988, Baïkoff and Joly11-14 presented the initial results obtained with the ZB phakic anterior chamber lenses for high myopia. Though results initially were promising, severe endothelial cell loss caused by the thick-edged optic appeared within the first 2 years.11,13 Because of this complication, the clinical investigation of the ZB lens was suspended.

In 1990, Baïkoff11-14 introduced the ZB 5M. The ZB 5M myopic IOL had optic dimensions of 5-mm diameter, an effective optical zone of 4 mm, thinned edges, and reduced lens curvature produced by moving the optic posterior 0.6 mm. The initial reports of the clinical results with this lens were good.11-14 With further follow-up, however, pupillary ovalization was seen in 16.38% to 22.6% of eyes after a mean follow-up of 35.8 and 58.6

months, respectively. This had no clinical significance in the majority of cases but did lead to severe iris atrophy in one of the eyes. Similarly, later reports11-14 suggested continued endothelial cell loss as high as 14.8%.

Following the ZB 5M (Bausch & Lomb Surgical, Rochester, NY), Baïkoff11-14 introduced the NuVita MA20 (Bausch & Lomb Surgical, Rochester, NY) myopic implant, which had an effective optical zone of 4.5 mm, a forward convex anterior lens face of the lens, and antireflective edges. The optical results were similar to those of the ZB implants; however, the pupillary ovalization was considerably reduced to less than 4% to 5%.

In 1991, Worst introduced the myopia claw lens.24 The first design had a 4.5-mm optic diameter and a negatively powered biconcave lens for myopic phakic eyes. Later, the optic was altered into a convex-concave shape and the optical diameter increased to 5.0 mm to reduce halos and glare. In 1998, the lens was renamed the Artisan myopia lens (Ophtec BV, Groningen, Netherlands)25-29 and the design changed to a 6-mm optical diameter for all powers up to -15.50 D.

Alio et al30,31 have helped to summarize the complications associated with angle-supported phakic anterior chamber IOL implantation. They prospectively studied 263 eyes of 160 patients implanted with the Baïkoff ZB 5M and the ZSAL-4 (Morcher GmbH, Stuttgart, Germany). Follow-up was from 1 to 7 years. Postoperative iritis overall was reported at 4.56%. Night halos and glare were reported, but the larger optic size with the Phakic 6H2 has substantially reduced this complication. High intraocular pressure was noted in 7.2% of cases, likely related to incomplete viscoelastic removal. Perhaps the most critical factor reported was endothelial cell loss. At month 3, there was 1.83% cell loss reported. At year 1, it was 3.86% loss. At 7 years, the total cumulative loss of central endothelial cells was 8.3%. Pupil ovalization

168 Chapter 16

occurred in 5.9%. Retinal detachment was observed in 3% of cases.30,31

With respect to endothelial cell loss, earlier models of both angle-fixated and iris-fixated lenses were associated with higher endothelial cell loss for reasons previously mentioned.11,20,21,30-32

The latest design change in the evolution of angle-fix- ated IOLs for the treatment of myopia is the Phakic 6H2 lens.15 This lens has a 6-mm optic to minimize halos and glare, and the footplates have a novel “ski tip” design that helps to prevent iris capture in the angle. In the Phakic 6H2 lens, the haptics are extremely flexible, which prevents the anterior displacement of the lens with peripheral compression. It is hoped that these design changes will significantly reduce the problems seen with anterior chamber phakic myopic lenses. Specifically, the flexible haptic design and the thinner optic are designed to minimize any progressive endothelial cell loss. The novel “ski tip” haptics and the heparin coating are designed to minimize the possibility of iris capture and iris inflammation, both factors which can lead to pupil ovalization.15

The results from this preliminary study demonstrate the safety and efficacy of the Phakic 6H2 myopic IOL. Specifically, we found the nomogram to be accurate. In addition, there was no prolonged high intraocular pressure, iris inflammation, or pupil ovalization. Further longterm studies are ongoing and essential to examining the endothelial cell loss.

SUMMARY

The Phakic 6H2 lens has a design that may reduce the complications that have plagued previous myopic phakic IOLs. Phakic anterior chamber lens designs have been successively modified, leading to the development of the Phakic 6H2 design. The results to date are promising, but further long-term studies are needed to ensure the safety and efficacy in the moderate to high myopic population.

REFERENCES

1.Werner L, Apple D, Izak A, et al. Phakic anterior chamber intraocular lenses. Int Ophthalmol Clin. 2001;41(3):133151.

2.Barraquer J. Modification of refraction by means of intracorneal inclusions. Int Ophthalmol Clin. 1966;6(1):53-78.

3.Drews RC. The Barraquer experience with intraocular lenses, 20 years later. Ophthalmology. 1982;89:386-393.

4.Choyce DP. Intraocular lenses and Implants. London: HK Lewis; 1964:153-155.

5.Choyce DP. Comparison of Choyce lenses. J Cataract Refract Surg. 1987;13:344-345.

6.Choyce DP. The correction of high myopia. Refractive & Corneal Surgery. 1992;8(3):242-245.

7.Horgan S, Fraser, S, Choyce, DP. Twelve year follow-up of unfenestrated polysulfone intracorneal lenses in human sighted eyes. J Cataract Refract Surg. 1996;22:1045-1051.

8.Fechner P, van der Heijde G, Worst J. The correction of myopia by lens implantation into phakic eyes. Am J Ophthalmol. 1989;107:659-663.

9.Fechner P, Strobel J, Wichmann W. Correction of myopia by implantation of a concave Worst iris-claw lens into phakic eyes. Refractive & Corneal Surgery. 1991;7:286-298.

10.Praeger DL, Momose A, Muroff L. Thirty-six month followup of a contemporary phakic intraocular lens for the surgical correction of myopia. Ann Ophthalmology. 1991;23:6- 10.

11.Baïkoff G, Colin J. Damage to the corneal endothelium using anterior chamber intraocular lenses for myopia.

Refractive & Corneal Surgery. 1990;6(5):383.

12.Baïkoff G. Phakic anterior chamber intraocular lenses. Int Ophthalmol Clin. 1991;31(1):75-86.

13.Baïkoff G, Arne J, Bokobza Y, et al. Angle-fixated anterior chamber phakic intraocular lens for myopia of -7 to -19 diopters. J Refract Surg. 1998;14(3):282-293.

14.Baïkoff G. Intraocular phakic implants in the anterior chamber. Int Ophthalmol Clin. 2000;40:223-235.

15.Galin MA, Hirschman H. A Surgical Protocol for Implantation of Phakic 6H2. Ontario, Canada: Ophthalmic Innovations International, Inc; 2001.

16.Holladay JT. Refractive power calculations for intraocular lenses in the phakic eye. Am J Ophthalmol. 1993;16:63-66.

17.Werblin TP. Barraquer Lecture 1998. Why should refractive surgeons be looking beyond the cornea? J Refract Surg. 1999;15(3):357-376.

18.Downing J, Parrish C. Long-term results with Choyce-

Tennant anterior chamber intraocular lens implants.

J Cataract Refract Surg. 1986;12:493-498.

19.Perez-Santonja J, Iradier M. Chronic subclinical inflammation in phakic eyes with intraocular lenses to correct myopia. J Cataract Refract Surg. 1996;22:183-187.

20.Perez-Santonja J, Iradier M, et al. Endothelial changes in phakic eyes with anterior chamber intraocular lenses to correct high myopia. J Cataract Refract Surg. 1996;22:10171022.

21.Mimouni F, Colin J, Koffi V, et al. Damage to the corneal endothelium from anterior chamber intraocular lenses in phakic myopic eyes. Refractive & Corneal Surgery. 1991;7:277-281.

22.Saragoussi JJ, Cotinat J, Renard G, et al. Damage to the corneal endothelium by minus power anterior chamber intraocular lenses. Refractive & Corneal Surgery.

1991;7:282-285.

23.Kaufman H, Kaufman SC, Beuerman RW. In defense of phakic anterior chamber lenses. J Cataract Refract Surg. 1997;23:815-817.

24.Landesz M, Worst J, van Rij G. Long-term results of correction of high myopia with an iris-claw phakic intraocular lens. J Refract Surg. 2000;16:310-316.

25.Maloney, RK, Nguyen LH, John M. Artisan phakic intraocular lens for myopia. Ophthalmology. 2002;109(9):16311641.

26.Malecaze F, Hulin H, Pascal B, Fournié P. A randomized paired eye comparison of two techniques for treating moderately high myopia. Ophthalmology. 2002;109(9):16221630.

27.Perez-Santonja J, Alio J, Jiminez-Alfaro I, Zato M. Surgical correction of severe myopia with an angle-supported phakic intraocular lens. J Cataract Refract Surg. 2000;26:12881302.

28.Gimbel H, Ziemba S. Management of myopic astigmatism with phakic intraocular lens implantation. J Cataract Refract Surg. 2002;28:883-886.

29.O’Brien T, Awwad S. Phakic intraocular lenses and refractory lensectomy for myopia. Current Opin Ophthalmol. 2002;13:264-270.

30.Alio JL, de la Hoz F, Perez-Santonja JJ, et al. Phakic anterior chamber lenses for the correction of myopia, a 7-year cumulative analysis of complications in 263 cases. Ophthalmology. 1999;106(3):458-466.

31.Landesz M, Worst JG, Van Rig G, et al. Long-term results

of correction of high myopia with an iris-claw PCIOL. J Refract Surg. 2000;16:310-316.

32.Waring, G. Phakic intraocular lenses for the correction of myopia—where do we go from here? Refractive & Corneal Surgery. 1991;7:275-276.