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

Figure 12-18A. A comparison of the effect on image quality from induced spherical aberration observed with the ICL vs LASIK.

aberration is useful for a quantitative comparison of outcomes, the effect on image quality using image simulations provides a qualitative comparison that is useful. The results indicate that spherical aberration and coma are the major differences between post-LASIK and phakic IOL higherorder aberrations, and simulated retinal images can be used to visualize the effects of these differences on vision (Figure 12-18).

CONCLUSION

The recovery of visual acuity is rapid with the ICL and commonly the quality of vision is excellent just minutes after surgery. Many reports documenting the efficacy of the ICL have been published. Short-term results with the ICL have been encouraging, and collamer ICLs have been relatively free of complication. Anterior subcapsular opacities have been reported, primarily in patients with incorrectly sized implants, inadequate ICL vault, or silicone material. Bioptics, which combines LASIK and the ICL for extreme cases of myopia, has also shown promise.31 Established long-term safety and experience will ultimately influence the range of correction for which the ICL is offered. Provided the overall incidence of complications remains low, it seems likely that the ICL will gain increased acceptance as an alternative to corneal refractive procedures.

REFERENCES

1. Arne JL, Lesueur LC. Phakic posterior chamber lenses for high myopia: functional and anatomical outcomes.

J Cataract Refract Surg. 2000;26:369-374.

Figure 12-18B. A comparison of the effect on image quality from induced spherical aberration observed with the ICL vs LASIK.

2.Assetto V, Benedetti S, Pesando P. Collamer intraocular contact lens to correct high myopia. J Cataract Refract Surg. 1996;22(5):551-556.

3.BenEzra D, Cohen E, Karshai I. Phakic posterior chamber intraocular lens for the correction of anisometropia and treatment of amblyopia. Am J Ophthalmol. 2000;130:292296.

4.Fink AM, Gore C, Rosen E. Cataract development after implantation of the STAAR Collamer posterior chamber phakic lens. J Cataract Refract Surg. 1999;25(2):278-282.

5.Fink AM, Gore C, Rosen ES. Overcorrected radial keratotomy treated with posterior chamber phakic intraocular lens and laser thermal keratoplasty. J Refract Surg. 1999;15:683686.

6.Garcia-Feyod J, Alfaro IJ, Cuino-Sardina R, et al. Ultrasound biomicroscopy examination of posterior chamber phakic intraocular lens position. Ophthalmology. 2003;110:163-172.

7.Garcia M, Gonzalez C, Pascual I, et al. Magnification and visual acuity in highly myopic phakic eyes corrected with an anterior chamber intraocular lens versus by other methods.

J Cataract Refract Surg. 1996;22:1416-1422.

8.Gonvers M, Othenin-Girard P, Barnet C, et al. Implantable contact lens for moderate to high myopia: short-term fol- low-up of 2 models. J Cataract Refract Surg. 2001;27(3): 380-388.

9.Hsuan JD, Caesar RH, Rosen PH, Rosen ES, Gore CL. Correction of pseudophakic anisometropia with the STAAR Collamer implantable contact lens. J Refract Surg. 2002;28(1):44-49.

10.Jimenez-Alfaro I, Benitez del Castillo JM, Garcia-Feijoo J, et al. Safety of posterior chamber phakic intraocular lenses for the correction of high myopia: anterior segment changes after posterior chamber phakic intraocular lens implantation. Ophthalmology. 2001;108(1):90-99.

11.Kohnen T, Baumeister M, Magdowski G. Scanning electron microscopic characteristics of phakic intraocular lenses. Ophthalmology. 2000;107:934-939.

12.Lesueur LC, Arne JL. Phakic posterior chamber lens implantation in children with high myopia. J Cataract Refract Surg. 1999;25:1571-1575.

13.Lovisolo CF, Pessando PM. The Implantable Contact Lens (ICL) and Other Phakic IOLs. Belbo, Italy: Fabiano; 1999.

14.Menezo JL, Peris-Martinez C, Cisneros A, et al. Posterior chamber phakic intraocular lenses to correct high myopia: a comparative study between STAAR and Adatomed models. J Refract Surg. 2001;17(1):32-42.

15.Pesando PM, Ghiringhello MP, Tagliavacche P. Posterior chamber collamer phakic intraocular lens for myopia and hyperopia. J Refract Surg. 1999;15(4):415-423.

16.Rosen ES. Phakic intraocular lenses and patient consent.

J Cataract Refract Surg. 1999;25:153-155.

17.Rosen E, Gore C. STAAR Collamer posterior chamber pha-

kic intraocular lens to correct myopia and hyperopia.

J Cataract Refract Surg. 1998;24(5):596-606.

18.Sanders DR. Actual and theoretical risks of visual loss following use of the implantable contact lens (ICL) for moderate to high myopia. J Cataract Refract Surg. In press.

19.Sanders DR, Vukich JA. Comparison of implantable contact lens (ICL) and laser assisted in-situ keratomileusis (LASIK) for moderate to high myopia. Cornea. In press.

20.Sanders DR, Brown DC, Martin RG, et al. Implantable contact lens for moderate to high myopia: Phase I FDA clinical study with 6 month follow-up. J Cataract Refract Surg. 1998;24(5):607-661.

21.Sanders DR, Vukich JA. The Implantable Contact Lens in Treatment of Myopia (ITM) Study Group. US Food and Drug Administration clinical trial of the implantable contact lens for low myopia. J Refract Surg. In press.

22.Sarver EJ, Sanders DR, Vukich JA. Comparison of image quality for high myopes corrected with laser in-situ keratomileusis and phakic intraocular lens. J Refract Surg. In press.

23.The Implantable Contact Lens in Treatment of Myopia (ITM) Study Group. Incidence of lens opacities and clinically significant cataracts with the implantable contact lens (ICL): comparison of 2 lens designs. J Refract Surg. 2002;18:673-682.

24.The Implantable Contact Lens in Treatment of Myopia (ITM) Study Group. Postoperative inflammation following implantation of the implantable contact lens. Ophthalmology. In press.

25.The Implantable Contact Lens in Treatment of Myopia (ITM) Study Group. US Food and Drug Administration clinical trial of the implantable contact lens for moderate to high myopia. Ophthalmology. 2003;110:255-266.

26.Trindade F, Pereira F. Cataract formation after posterior chamber phakic intraocular lens implantation. J Cataract Refract Surg. 1999;24(12):1661-1663.

27.Trindade F, Pereira F. Exchange of a posterior chamber phakic intraocular lens in a highly myopic eye. J Cataract Refract Surg. 2000;26:773-776.

28.Trindade F, Pereira F, Cronemberger S. Ultrasound biomicroscopic imaging of posterior chamber intraocular lens. J Refract Surg. 1998;14(5):497-503.

29.Uusitalo RJ, Aine E, Sen NH, Laatikainen L. Implantable contact lens for high myopia (1). J Cataract Refract Surg. 2002;28(1):29-36.

30.Zadok D, Chayet A. Lens opacity after neodymium:YAG laser iridectomy for phakic intraocular lens implantation.

J Cataract Refract Surg. 1999;25:592-593.

31.Zaldivar R, Davidorf JM, Oscherow S, et al. Combined posterior chamber phakic intraocular lens and laser in-situ keratomileusis: bioptics for extreme myopia. J Refract Surg. 2000;15:299-308.

32.Zaldivar R, Davidorf JM, Oscherow S. Posterior chamber phakic intraocular lens for myopia of -8 to -19 diopters. J Refract Surg. 1998;14(3):294-305.

33.Zaldivar R, Rocha G. The current status of phakic intraocular lenses. Int Ophthalmol Clin. 1996;36:107-111.

34.Zaldivar R, Ricur G, Oscherow S. The phakic intraocular lens implant: in-depth focus on posterior chamber phakic IOLs. Curr Opin Ophthalmol. 2000;11(1):22-34.

35.Zaldivar R, Oscherow S, Ricur G. The STAAR posterior chamber phakic intraocular lens. Int Ophthalmol Clin. 2000;40:237-245.

The Artisan phakic intraocular lens (IOL) (Ophtec BV, Groningen, Netherlands) was first introduced for the correction of high myopia. The correction of patients with high myopia who are unhappy with spectacle or contact lens correction presents a challenge to refractive surgeons. Laser in-situ keratomileusis (LASIK) for the correction of myopia greater than 6 diopters (D) involves several issues. The accuracy and safety is less for high myopia than for low myopia. As more tissue is removed and the optical zone is smaller, glare and halos become more common in high myopia. Because of excessive corneal thinning, corneal ectasia has been reported.1 The Artisan phakic IOL is implanted surgically and is not dependent on corneal wound healing. Thus, the Artisan lens has the potential for a more accurate and stable refractive correction.2 For these reasons, phakic IOLs like the Artisan lens have presented a new and exciting alternative treatment for high myopia and hyperopia.

HISTORY

The first iris-claw lens was used in cataract surgery for the correction of aphakia. It has been implanted in approximately 3000 aphakic eyes worldwide. Fechner and Worst modified the iris-claw lens in 1986 into a negatively biconcave lens to correct high myopia. The optic design was changed into a convex-concave model in 1991 and was known as the Worst myopia claw lens. The optic diameter was also increased from 4.5 mm to 5 mm, and the somewhat prominent rim of the biconcave lens was lowered. These changes were made to decrease the risk of damage

to the endothelium and to reduce the incidence of glare. In 1998 the name of the Worst claw lens was changed to the Artisan lens without a change in lens design.

THE ARTISAN LENS

The Artisan phakic lens is an iris-supported IOL. The lens haptics attach to the midperipheral, immobile iris through a process called enclavation. In this technique, the surgeon draws small knuckles of peripheral iris into the pincer-like haptics. Thus, the optic lies just anterior to the iris plane.

The Artisan lens is manufactured from Perspex CQ-UV (ICI, London, England) polymethylmethacrylate (PMMA). It has a vaulted design (Figure 13-1) to provide optimal clearance between the IOL and the crystalline lens and between the IOL and the corneal endothelium. The overall size of the lens is 8.5 mm in length. The distance from the edge of the optic to the corneal endothelium is approximately 1.5 to 2.0 mm, depending on the anterior chamber depth and the dioptric power.

Several studies have measured the intraocular position of the Artisan lens using ultrasound biomicroscopy preoperatively and postoperatively. In three myopic eyes, the anterior chamber depth was found to decrease by 28% to 34% and the distance between the crystalline lens and the posterior surface of the IOL ranged from 0.78 to 0.93 mm.3 In four hyperopic eyes, the anterior chamber depth ranged from 2.70 to 3.25 mm preoperatively and from 2.03 to 2.54 mm postoperatively, a decrease of about 30%.4 The distance between the anterior lens and the pos-

134 Chapter 13

Figure 13-1. Illustration of the vaulted design of the Artisan phakic IOL.

Figure 13-2B. The 5-mm optic Artisan lens (courtesy of Ophtec USA Inc).

terior surface of the Artisan lens ranges from .35 to .79 mm. Therefore, there is a measurable space between the crystalline lens and IOL in both hyperopic and myopic eyes. As well, there is a decrease in the depth of the anterior chamber with implantation of a lens, but the significance of this change is not known.

There are two models of the Artisan lens. The 5-mm lens for myopia is available in -3.0 to -23.0 D (Figure 13- 2). A 6-mm optic lens was introduced in 1997 (Figure 13- 3) and is available in -3.0 to -15.50 D. Since 1997, the 6-mm optic and 5-mm optic lenses have been available in 0.5 D increments. Both lens designs are exactly the same and differ only in the diameter of the optic. The total height of either lens does not exceed 0.95 mm. Lenses with higher powers are thicker than those with lower powers and, therefore, come closer to the corneal endothelium. To avoid endangering the corneal endothelium, the 6-mm diameter optic lens is made only up to -15.50 D.

Indications

Indications for the Artisan IOL include patients 18 years or older with stabilized myopia or hyperopia, as demonstrated by a change of less than or equal to 1.0 D for at least 12 months prior to the preoperative examination. Patients should be in good general health and without eye disease.

Figure 13-2A. The 5-mm optic Artisan lens (courtesy of Ophtec USA Inc).

PATIENT SELECTION

The Artisan lens was first used in the treatment of patients with high myopia. Subsequently, an Artisan lens for high hyperopia was introduced, followed by a toric phakic IOL for high myopes and hyperopes with astigmatism. These patients may be unhappy with spectacle correction, as thick lenses are required and can produce magnification or minification of images, aberrations, and limitation of visual field. Contact lenses are also an option, but there are risks associated with contact lens wear. Additionally, some patients are contact lens intolerant.

LASIK has been used to successfully treat low and moderate myopia, but in high myopia several complications have been reported, including corneal ectasia, severe night glare, and significant loss of best spectacle-corrected visual acuity (BSCVA). Clear lens extraction (CLE) has been performed. However, eyes with high myopia have an increased risk of retinal detachment following CLE. Young patients undergoing CLE lose their ability to accommodate. For these reasons, studies have examined the Artisan lens as an alternative treatment for high myopia, hyperopia, and high myopia and hyperopia with astigmatism.

CONTRAINDICATIONS

There are several contraindications to the use of the Artisan lens, including uveitis, endothelial counts less than 2000 cells/mm2, anterior chamber depth less than 2.6 mm, and glaucoma (Table 13-1).

PREOPERATIVE EVALUATION

Every patient considering Artisan lens implantation should have a complete eye examination, including slit lamp biomicroscopy, manifest and cycloplegic refraction, gonioscopy, B-scan biometry, tonometry, corneal topography and keratometry, and retinal examination. The physician should look for evidence of glaucoma, uveitis, or retinal disease. Corneal endothelial cell density should be calculated.

Figure 13-3A. The 6-mm optic Artisan lens (courtesy of Ophtec USA Inc).

Figure 13-3B. The 6-mm optic Artisan lens (courtesy of Ophtec USA Inc).

SURGERY

The technique of Artisan implantation is similar to other types of intraocular surgery. However, the process of iris enclavation is a unique aspect of the surgery that requires practice.

Power Calculation

The power of the lens is calculated by the van der Heijde formula. The measurements used in this formula are independent of axial length and include the anterior chamber depth, the corneal curvature, and the refraction.

K is the keratometric value of the cornea (D), Ps is the equivalent spectacle power of the corneal place (D), d is the distance (mm) between the IOL plane and the corneal plane, and n is the refractive index of aqueous (1.336). In the formula, the anterior chamber depth is the distance from the anterior corneal surface to the anterior surface of the IOL. This distance is approximately 0.8 mm in front of the crystalline lens. It is, therefore, necessary to subtract

0.8 mm from the anterior chamber depth as measured preoperatively using ultrasound.

The most commonly used method to calculate the IOL power is the van der Heijde nomogram (Table 13-2).

Surgical Technique

The pupil should be constricted preoperatively with 1% pilocarpine to reduce pupil size and prevent damage to the crystalline lens. General, local, or topical anesthesia may be used. The eye should be prepped with povidoneiodine solution. Two paracentesis sites are made at the 9:30 and 2:30 positions. These sites are needed to allow an entry site for enclavation of the iris to secure the lens. Therefore, the site is directed toward the midperipheral iris instead of the center of the lens as would be done in cataract surgery. The anterior chamber is then filled with viscoelastic.

The axis of astigmatism should be taken into consideration in choosing a wound location. The most common wound site is superior, but the technique is the same temporally. Several incision types are used: clear corneal, limbal, corneoscleral, and scleral. Good wound construction will minimize the possibility of induced astigmatism or wound leak. A 5.0- to 5.5-mm incision is needed for insertion of 5-mm optic lens, and a 6.0- to 6.5-mm incision is needed for the 6-mm lens. After the wound is made, additional viscoelastic is instilled. The surgeon should be careful not to dilate the pupil, allow viscoelastic under the iris, or push the iris too far posteriorly, making enclavation of the iris difficult.5

The implant is then advanced into the eye using longangled forceps and rotated 90 degrees to a horizontal position in the center of the anterior chamber with a Sinskey or Kuglan hook (Katena, Denville, NJ). The lens should be

Figure 13-4. The Artisan enclavation needle (courtesy of Ophtec USA Inc).

centered on the pupil and held in position with the Artisan implantation forceps during the enclavation process. An enclavation needle (Figure 13-4) or fine iris forceps are then used to catch a small fold of iris and engage it in the claw of the implant (Figure 13-5). The needle or iris forceps hold the fold of iris while the Artisan lens is depressed slightly with the implantation forceps so that the claws will automatically grasp the iris. The second haptic is then secured to the iris in a similar fashion.

Centration of the optic should be noted. If the lens is not well-centered, the iris can be released by pushing in the central portion of the claw with the needle. Repositioning and enclavation can then be performed. One advantage of the Artisan lens over angle-fixated or sulcus-fixated lenses is that it can be centered on the pupil, even if the pupil is not perfectly centered in relationship to the limbus.5

A peripheral iridotomy is performed to prevent pupillary block. Alternatively, a neodymium:yttrium-aluminum- garnet (Nd:YAG) peripheral iridotomy can be performed postoperatively. The wound is then sutured. Postoperatively, topical antibiotic is given, as well as steroid and/or nonsteroidal drops.

RESULTS

Phase III US Food and Drug Administration Trial for Myopia

The Phase III Interim Report for the Food and Drug Administration (FDA) trial for the Artisan lens for myopia was compiled by Ophtec in December 2002.6 This multicenter FDA trial evaluated data from 536 eyes implanted with the Artisan lens for myopia.

Study Population

Five hundred thirty-six eyes of 536 patients were implanted with the Artisan lens for myopia. The mean age of the patients was 39 years. The anterior chamber depth ranged from 3.02 to 4.67 mm with a mean of 3.71 mm. The incision created by the surgeon was approximately one-third corneal, one-third scleral, and one-third limbal. Sixty-nine percent of surgeons chose a superior location for the wound, while 31% chose a temporal approach. Four hundred sixteen eyes received the 6-mm optic lens,

The Artisan Phakic Intraocular Lens 137

Figure 13-5. The enclavation process. The Artisan lens is held in place with lens forceps while the iris is engaged in the claw of the haptic (courtesy of Ophtec USA Inc).

and 120 eyes received the 5-mm optic lens. The power of the implants used ranged from -5.00 D to -20.0 D with a mean power of -12.68 D.

Results

Patients were seen postoperatively up to 36 months. Four hundred sixteen of 536 eyes were seen in follow-up at 6 months postoperatively. Uncorrected visual acuity (UCVA) at 6 months was 20/40 or better in 86.8% of patients. Three hundred fifty-seven patients were seen 12 months postoperatively, where 87.3% of eyes had UCVA of 20/40 or better. At 6 months, 99.8% of eyes had BSCVA of 20/40 or better, compared to 99.3% preoperatively.

Additional Studies

Maloney et al2 published results from patients who received Artisan implants as part of the Phase I, II, or III FDA trial (Table 13-3). One hundred fifty-five eyes were included, with a mean refraction of -12.69 -3.80 D with a range of -5 D to -22.5 D. At 6 months, 85% of eyes had UCVA of 20/40 or better, and 90% of eyes were within 1.0 D of intended correction. At 6 months, no eye had lost two or more lines of BSCVA.

A European multicenter study included data from 518 patients implanted with the Artisan lens for myopia.7 The mean spherical equivalent preoperatively was -12.95 4.35 D. An UCVA of 20/40 or better was observed in 76.8% of patients. The BSCVA remained the same or improved in 95.8% of eyes, while three eyes lost two or more lines of acuity. One eye was due to cataract, and two involved macular myopic degeneration. In the group with high myopia (120 eyes, -11 to -15 D), 43.7% gained two or more lines of BSCVA. In the group with extremely high myopia (60 eyes, >-15 D), 63.3% or eyes gained two or more lines of BSCVA.

Menezo et al8 compiled data from 48 eyes receiving the original biconcave model and 46 eyes receiving the con- cave-convex model now used. The mean preoperative spherical equivalent was -14.73 4.31 D. At 3 years postoperatively, 94.6% of eyes were found to have UCVA of 20/40 or better. No eyes lost two or more lines of BSCVA, and 81.9% of eyes gained two or more lines of BSCVA. At

BSCVA imEndothelial cell loss

Mean -16.60 Mean 18.3 76.5

Perez-Santonja Worst bicon32

+ 6.29 D months

cave lens

17 alet

127

Worstcave -biconlens

18 alet

Fechner

Artisan lens 518

7 alet

Budo

lensArtisan 67

9 alet

Landesz

Implant power Up to 36 UCVA 20/40 BSCVA imGlare and halos 9.1%

Phase III Interim Artisan lens 536

6 Results