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

Figure 20-1. STAAR Surgical ICL (reprinted with permission from Zaldivar R, Oscherow S, Ricur G. The STAAR posterior chamber phakic intraocular lens. Int Ophthalmol Clin. 2000; 40(3):237-244).

Implantation of supplementary lenses is another alternative for the treatment of high refractive errors as well as pseudophakic ametropia. Gayton was the first to describe a technique of implanting two IOLs in a microphthalmic eye in 1993.19 Since then, the piggyback method of implanting two IOLs in one eye has expanded to address pseudophakic refractive error in normal eyes and eyes that have undergone postpenetrating keratoplasty. Piggyback implantation has been combined with the use of minus-power lenses to provide appropriate power for a cataract patient with keratoconus, as well as to correct pseudophakic myopia.20,21 Despite its success, the late complication of interlenticular cellular growth with resultant hyperopic shift, opacification, and loss of vision has recently become a concern.22,23

In search of a better alternative for the treatment of pseudophakic ametropia, the use of phakic IOLs in pseudophakic patients has been recently described. Chiou et al24 reported the use of a posterior chamber phakic Implantable Contact Lens (ICL) (STAAR Surgical AG, Nidau, Switzerland) in patients who had developed ametropia and anisometropia after unilateral phacoemulsification and in the bag IOL implantation. The STAAR Surgical ICL was originally designed for the correction of myopia and hyperopia in phakic patients (Figure 20-1). The ICL is constructed of a hydrophilic collagen/hydroxyethyl methacrylate copolymer collamer with a refractive index of 1.45 at body temperature. It is highly flexible and only 60 µm thick, which is approximately 10 to 20 times thinner than traditional IOLs (depending on the refractive index and power). It has the same advantages of successful IOL piggybacking, but is minimally invasive and may avoid interface opacities.18,25

In their report, Chiou et al treated two patients who had undergone traditional cataract phacoemulsification and in the bag IOL placement who subsequently complained of intolerable anisometropia.24 The manifest

Figure 20-2. Baïkoff or NuVita anterior chamber lens (reprinted with permission from Baïkoff G. Intraocular phakic implants in the anterior chamber. Int Ophthalmol Clin. 2000;40(3):223235).

refraction was - 6.00 - 0.50 x 50 in the first patient and +4.50 -1.00 x 15 in the second. Postoperatively, after ICL implantation in the ciliary sulcus, uncorrected visual acuity had improved from 20/400 to 20/30 in the first patient and from 20/200 to 20/40 in the second with manifest refractions of - 0.50 - 0.75 x 55 and + 1.50 - 1.50 x 30, respectively, after 1 year. They reported no complications.

Hsuan et al obtained similar results after implantation of the ICL in six eyes of pseudophakic patients to correct anisometropia. The preoperative range of anisometropia was 2.0 to 7.9 diopters (D). This was reduced to 0.0 to 3.5 D, with symptomatic resolution of the anisometropia in all patients.18

Currently, there are several different types of phakic IOLs for the treatment of myopia and hyperopia in clinical use: anterior chamber angle-fixated IOLs, posterior chamber sulcus-fixated IOLs, posterior chamber free-float- ing IOLs, and iris-supported IOLs. Anterior chamber lenses such as the Baïkoff or NuVita lens (Figure 20-2) (Bausch & Lomb Surgical, Rochester, NY),26 offer the advantage of easy insertion using a technique with which most cataract surgeons are familiar. Potential disadvantages include pupillary ovalization from fibrosis around the footplate in the anterior chamber angle or chronic compromise of the anterior chamber angle, leading to glaucoma.26-28 Posterior chamber sulcus-fixated IOLs, such as the ICL and the phakic refractive lens (PRL) (CIBA Vision, Duluth, Ga),29,30 which are foldable, offering the advantage of insertion through a small incision. They are placed far from the anterior chamber angle and the corneal endothelium. Potential disadvantages include angle closure from forward displacement of the iris, pigment dispersion from chafing, and cataract because of contact with the crys-

Figure 20-3. The Artisan phakic IOL (courtesy of Ophtec, Groningen, Netherlands).

talline lens.31 The third category of phakic IOL includes the anterior chamber iris-fixated lens or Worst-Fechner claw lens. This lens attaches to the peripheral iris through two pincer-like haptics. The only commercially available lens in the United States is the Artisan phakic IOL (Ophtec BV, Groningen, Netherlands) (Figure 20-3).32-34

To date, there have been no published reports of the placement of other phakic IOLs in pseudophakic eyes. Given the excellent outcomes of the Artisan lens in the treatment of high myopia in phakic eyes,34 we could speculate that this would be a reasonable alternative in those patients with pseudophakic ametropia. In theory, the risk of endothelial cell loss might be decreased considering the increased anterior chamber depth (ACD) in pseudophakic eyes. Placement of an anterior chamber-supported phakic IOL, such as the Baïkoff lens, might also be an alternative in the treatment of pseudophakic ametropia. Even though some reports of iris retraction and long-term endothelial loss have been reported with the Artisan lens, this lens may be promising as an alternative in the treatment of pseudophakic ametropia, especially with the newer foldable version that avoids the larger incision of the rigid style.35,36

As compared to other phakic IOLs, the ICL might offer several advantages. Because it was originally designed for use in phakic patients, it has a vaulted optic, which may decrease axial touch and reduce the incidence of interface opacities when used in piggyback implantation. In the pseudophakic eye, there is obviously no risk of cataract formation, which is the greatest risk in the phakic eye. Its posterior chamber position minimizes endothelial cell loss and trauma to the iris while preserving the advantage of the smallest possible incision.18 The ICL also offers the advantage of being reversible and not affecting the corneal refractive power. Sanders et al37 reported the predictability of the final refraction as well as the uncorrected and best-corrected visual acuities to be better in a series of myopic phakic patients given an ICL than in those treated

with PRK or LASIK. Despite its advantages, the ICL has other known risks, including the development of pupillary block (from inadequate iridectomies), increased intraocular pressure, and case reports of neovascularization of the angle and pigment deposition.38,39 Safe use of ICL requires the formation of patent iridotomies as well as correct sizing of the ICL based on the white-to-white distance.

Phakic IOLs may also have a role in the management of other eye conditions. Eyes with poor capsular support after phacoemulsification may benefit from the placement of angleor iris-supported IOLs offering a technically less demanding and time-consuming surgery than sutured sulcus fixated IOLs. Gabor obtained good results in 15 eyes of 12 patients with subluxated lenses in whom he implanted an Artisan lens after phacoemulsification.40

In pseudophakic eyes with high astigmatism and unsatisfactory correction with spectacles or contact lenses for medical, professional, or personal requirements, the new toric phakic IOLs may become a future alternative in addition to the current surgical options of keratorefractive procedures such as LASIK, PRK, or astigmatic keratotomy.41-43 In a recent European 6-month clinical trial by Dick et al,44 the implantation of the Artisan toric phakic IOL was demonstrated to be safe, predictable, and effective in reducing or eliminating high ametropia and astigmatism with one procedure in phakic patients.

SUMMARY

The use of phakic IOLs in pseudophakic patients may be a safe and effective alternative in the management of pseudophakic anisometropia. This technique may offer the advantage of a minimally invasive and reversible procedure. It may also be useful in introducing multifocal optics into the pseudophakic eye for correction of presbyopia. Only reports using the ICL are presently available. Similar success may be obtained with the use of other phakic intraocular lenses.

REFERENCES

1.Kershner RM. Refractive cataract surgery. Curr Opin Ophthalmol. 1998;9(1):46-54.

2.Koch DD, Liu JF, Hyde LL, et al. Refractive complications of cataract surgery after radial keratotomy. Am J Ophthalmol. 1989;108:676-682.

3.Lyle WA, Jin GJC. Intraocular lens power prediction in patients who undergo cataract surgery following previous radial keratotomy. Arch Ophthalmol. 1997;115:457-461.

4.Hamilton DR, Hardten DR. Cataract surgery in patients with prior refractive surgery. Curr Opinion Ophthalmol. 2003;14(1).

5.Sinskey RM, Amin P, Stoppel JO. Indications for and results of a large series of intraocular lens exchanges. J Cataract Refract Surg. 1993;19(1):68-71.

6.Oshika T, Yoshitomi F, Fukuyama M, et al. Radial keratotomy to treat myopic refractive error after cataract surgery.

J Cataract Refract Surg. 1999;25(1):50-55.

7.Helmy SA, Salah A, Badawy TT, Sidky AN. Photorefractive keratectomy and laser in situ keratomileusis for myopia between 6.00 and 10.00 diopters. J Refract Surg. 1996;12(3):417-421.

8.Sher NA, Hardten DR, Fundingsland B, et al. 193-nm excimer photorefractive keratectomy in high myopia. Ophthalmology. 1994;101(9):1575-1582.

9.Kremer FB, Dufek M. Excimer laser in situ keratomileusis. J Refract Surg. 1995;11(3 Suppl):S244-S247.

10.Hamilton DR, Hardten DR, Lindstrom RL. Conductive and thermal keratoplasty. In: Krachmer J, Holland EJ, eds. Cornea. St. Louis, Mo: Mosby Inc; 2003.

11.Filatov V, Vidaurri-Leal JS, Talamo JH. Selected complications of radial keratotomy, photorefractive keratectomy, and laser in situ keratomileusis. Int Ophthalmol Clin. 1997;37:123-148.

12.Maguen E, Machatt JJ. Complications of photorefractive keratectomy, primarily with the VISX Excimer Laser. In: Salz JJ, ed. Corneal Laser Surgery. St Louis, Mo: Mosby; 1995.

13.Davis EA, Hardten DR, Lindstrom RL. LASIK complications. Int Ophthalmol Clin. 2000;40(3):67-75.

14.Lin RT, Maloney RK. Flap complications associated with lamellar refractive surgery. Am J Ophthalmol. 1999;127(2):129-136.

15.Yu AK, Ng AS. Complications and clinical outcomes of intraocular lens exchange in patients with calcified hydrogel lenses. J Cataract Refract Surg. 2002;28(7):1217-1222.

16.Doren GS, Stern GA, Driebe WT. Indications for and results of intraocular lens explantation. J Cataract Refract Surg. 1992;18(1):79-85.

17.Lyle WA, Jin JC. An analysis of intraocular lens exchange. Ophthalmic Surg. 1992;23(7):453-458.

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

19.Gayton JL, Sanders VN. Implanting two posterior chamber intraocular lenses in a case of microphthalmos. J Cataract Refract Surg. 1993;19(6):776-777.

20.Fenzl RE, Gills JP 3rd, Gills JP. Piggyback intraocular lens implantation. Curr Opin Ophthalmol. 2000;11(1):73-76.

21.Gills JP, Fenzl RE. Minus-power intraocular lenses to correct refractive errors in myopic pseudophakia. J Cataract Refract Surg. 1999;25(9):1205-1208.

22.Gayton JL, Apple DJ, Peng Q, et al. Interlenticular opacification: clinicopathological correlation of a complication of posterior chamber piggyback intraocular lenses. J Cataract Refract Surg. 2000;26(3):330-336.

23 Werner L, Shugar JK, Apple DJ, et al. Opacification of piggyback IOLs associated with an amorphous material attached to interlenticular surfaces. J Cataract Refract Surg. 2000;26(11):1612-1619.

24.Chiou AG, Bovet J, de Courten C. Pseudophakic ametropia managed with a phakic posterior chamber intraocular lens. J Cataract Refract Surg. 2001;27(9):1516-1518.

25.Shugar JK, Schwartz T. Interpseudophakos Elschnig pearls associated with late hyperopic shift: a complication of pig-

26.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(5):282-293.

27.Baïkoff G, Joly P. Comparison of minus power anterior chamber intraocular lenses and myopic epikeratoplasty in phakic eyes. Refract Corneal Surg. 1990;6:252.

28.Baïkoff G. Intraocular phakic implants in the anterior chamber. Int Ophthalmol Clin. 2000;40(3):223-235.

29.Sanders DR, Brown DC, Martin RG, et al. Implantable contact lens for moderate to high myopia: phase 1 FDA clinical study with 6 month follow-up. J Cataract Refract Surg. 1998;24(5):607-611.

30.CIBA phakic IOLs show promising results for myopia and hyperopia. Presented at the ESCRS meeting; September 2002; Nice, France.

31.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.

32.Fechner PU, Haubitz I, Wichmann W, et al. Worst-Fechner biconcave minus power phakic iris-claw lens. J Refract Surg. 1999;15(2):93-105.

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

34.Maloney RK, Nguyen LH, John ME. Artisan phakic intraocular lens for myopia: short-term results of a prospective, multicenter study. Ophthalmology. 2002;109(9):16311641.

35.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. 2000;16(3):310-316.

36.Allerman N, Chamon W, Tanaka HM, et al. Myopic anglesupported intraocular lenses: two-year follow-up. Ophthalmology. 2000;107(8):1549-1554.

37.Sanders DR, Brown DC, Martin RG, et al. Implantable contact lens for moderate to high myopia: phase 1 FDA clinical study with 6 month follow-up. J Cataract Refract Surg. 1998;24(5):607-611.

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

39.Gonvers M, Othenin-Girard P, Bornet 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.

40.Gobor R. Artisan IOL after phacoemulsification in subluxated lenses. J Cataract Refract Surg. 2002;28(11):2064.

41.Davis EA, Lindstrom RL. Astigmatism management: ablation patterns. Curr Opin Ophthalmol. 2001;12(4):300-303.

42.Lindstrom RL, Agapitos PJ, Koch DD. Cataract surgery and astigmatic keratotomy. Int Ophthalmol Clin. 1994;34(2): 145-164.

43.The surgical correction of astigmatism: a clinician’s perspective. Refract Corneal Surg. 1990;6(6):441-454.

44.Dick HB, Alio J, Bianchetti M, et al. Toric phakic intraocular lens: European multicenter study. Ophthalmology. 2003;110(1):150-162.

INTRODUCTION

Future developments in phakic intraocular lenses (IOLs) will focus on optimizing lens designs to decrease long-term anterior segment complications; afford easier, less invasive surgical techniques; and expand clinical indications. We have already seen some of the design improvements in angle-fixated anterior chamber phakic IOLs to decrease endothelial cell loss and improve visual function (see Chapter 17). Similar design improvements will likely be required to reduce incidence of cataract formation from implant/natural lens touch with posterior chamber phakic IOLs.1,2 A recent report by Sanders et al compares the incidence of anterior subcapsular opacities, poor lens vault, and clinically significant cataracts between the now discontinued V3 design (87 eyes) and the newer V4 design (523 eyes) of the Implantable Contact Lens (ICL) (STAAR Surgical, Nidau, Switzerland). The V4 design has an additional 0.13 to 0.21 mm of anterior vault, depending on the dioptric power of the lens (Figure 21-1). The study reports a statistically significant reduction in the incidence of late anterior subcapsular opacities (9.2% V3 vs 0.6% V4) and clinically significant cataracts (9.2% V3 vs 0.8% V4).3

This chapter will examine foldable, toric anterior chamber phakic IOLs, ultrathin lenses, light-adjustable IOLs, and the exciting new frontier of accommodative IOLs. In addition to new lens designs, this chapter will discuss a new indication for IOLs: the treatment of severe anisometropic amblyopia.

NEW APPLICATION:

ANISOMETROPIC AMBLYOPIA

Anisometropia is a significant risk factor for the development of amblyopia, particularly in high unilateral myopia. In addition, the condition is difficult to treat using the conventional technique of spectacle or contact lens correction with occlusion, particularly when the anisometropia is greater than 3.00 diopters (D).4,5 Refractive surgery has been used recently to treat anisometropic amblyopia with encouraging results.6-9 The healing process of the pediatric cornea, however, is not wellunderstood, as evidenced by higher incidence of postoperative haze in these studies, even in cases in which laser in-situ keratomileusis (LASIK) was used. In addition, the refractive status of the pediatric patient changes frequently. Techniques that remove corneal tissue may be suboptimal under such dynamic circumstances, ultimately limiting future enhanceability. Lastly, very young pediatric patients may not be able to cooperate with the fixation required during keratorefractive procedures.

The use of phakic IOLs may afford a more appropriate solution for the treatment of anisometropic amblyopia.10 A recent study by Lesueur and Arne examined the use of the ICL and postoperative patching to treat 12 eyes in patients ranging from age 3 to 16 with high myopic amblyopia (preoperative mean spherical equivalent: -12.70 D, range: -8.00 to -18.00 D).11 With a mean follow-up of 20.5 months, all eyes except one gained lines of best corrected acuity with 70% of eyes gaining more than two

Figure 21-1. Schematic demonstrating the difference in vaulting characteristics between the V3 and V4 designs of the ICL. In this -14.50 D ICL sectioned along its long axis, the V4 design demonstrates 0.17 mm more vault compared to the V3 design (reprinted with permission from Sanders DR, Vukich JA, ICL in Treatment of Myopia Study Group. Incidence of lens opacities and clinically significant cataracts with the ICL: comparison of two designs. J Refract Surg. 2002;18:674).

Figure 21-2. Artisan phakic toric intraocular lens (courtesy of Ophtec).

lines of best corrected acuity. A trend toward lower increase in axial length of operated eyes compared to unoperated eyes was noted. Strabismus improved in all patients following surgery, with four exotropic patients recovering orthophoria postoperatively without strabismus surgery and six patients recovering binocular vision. There were significant gains in the quality of life reported among all patients. No significant complications were reported.

TORIC PHAKIC INTRAOCULAR LENSES

While the intraocular correction of astigmatism in the phakic eye is currently in its infancy, there may be distinct advantages of this method over keratorefractive techniques. Current LASIK and surface ablation techniques alter the corneal curvature from the ideal prolate shape to a less optically ideal oblate shape. A toric phakic IOL, by contrast, maintains natural corneal asphericity. In addition, IOL implantation is reversible while ablative keratorefractive techniques are “enhanceable” but not truly reversible, as corneal tissue is removed with each treatment.

The Toric Implantable Contact Lens

At the time of publication, there are several phakic IOLs being investigated for the treatment of myopic astigmatism. The first toric posterior chamber phakic IOL was implanted by Thomas Neuhann, MD in Munich, Germany in 1999 (unpublished data). The first implantation in North America, a toric version of the STAAR ICL, was recently reported by Gimbel and Ziemba.12 The 48-year- old patient had a manifest refraction of -11.50 +2.25 x 008. Preoperative laser peripheral iridotomies were performed at 11:00, 12:00, and 1:00 positions. The ICL (-16.00 +3.50 x 002) was implanted through a 3.0-mm

clear corneal temporal incision and rotated to align with a mark at 180 degrees placed on the sclera preoperatively at the slit lamp. Uncorrected visual acuity was 20/15-3 at 1 day and 20/15 at 5 months with a manifest refraction of plano +0.25 x 150. There were no early or late complications seen. The STAAR toric ICL, based on the V4 design, recently received marketing approval in Europe after demonstrating rotational stability in eyes followed for 1 year.13 Clinical trials are ongoing in the United States. The PRL does not have a toric version implanted to date, as there is no rotational fixation of this posterior chamber phakic IOL.

The Artisan Phakic

Toric Intraocular Lens

Artisan phakic toric IOLs, currently custom made by Ophtec BV (Groningen, Netherlands), are designed for the correction of regular astigmatism in combination with myopia or hyperopia. Ophtec provides a recommendation for the lens power and a special drawing indicating the proper axes in which the lens should be implanted for each individual case. The one-piece compression molded phakic toric IOL is made of polymethylmethacrylate (PMMA) and benzotriazole featuring a 5.0-mm, convex-concave optic and overall length of 8.5 mm (Figure 21-2). The anterior surface is spherical while the posterior surface is spherocylindrical. The lenses are available from -3.0 to -23.5 D for myopia and from +2 to +12 D for hyperopia with cylindrical correction from 1.0 to 7.0 D.

Most surgeons implanting the spherical Artisan lens prefer to position the IOL horizontally through a 12:00 incision. In keeping with this surgical technique, the Artisan phakic toric IOL has been designed in two models to allow the lens to be positioned in an oblique horizontal position, regardless of the axis of astigmatism (Figure 21-

Figure 21-3A. Two models of Artisan phakic toric IOL. Model A has the torus axis oriented along the long axis of the lens and is designed for eyes with refractive astigmatic axis from 0 to 45 degrees or 135 to 180 degrees. In this example, the lens is enclavated 15 degrees counterclockwise from the horizontal to treat -15.0 -5.0 x 015 (courtesy of Ophtec).

Figure 21-3B. Two models of Artisan phakic toric IOL. Model B has the torus axis oriented along the vertical axis of the lens and is designed for eyes with refractive astigmatic axis between 45 and 135 degrees. In this example, the lens is enclavated 10 degrees clockwise from the horizontal to treat +4.0 -6.0 x 080 (courtesy of Ophtec).

3). Model A is a negative cylinder lens that has the torus axis running through the horizontal axis (ie, at 0 degrees). It is intended for implantation in eyes with astigmatic axes between 0 and 45 degrees or between 135 and 180 degrees. Model B is a negative cylinder lens that has the torus axis running through the vertical axis (ie, 90 degrees from the long axis of the lens). It is intended for implantation in eyes with astigmatic axes between 45 and 135 degrees. Positive and negative cylinder lenses are available. The axis of enclavation has to be exact. Consequently, marking the axis on the iris with argon laser or on the sclera at the slit lamp preoperatively is essential.

The results of a large prospective, multicentral trial from 15 centers examining the efficacy and safety of the Artisan phakic toric IOL in 70 eyes of 53 patients with 6-month follow-up was recently reported.14 The study looked at both myopic astigmatism (group A: N = 48, mean preoperative spherical equivalent [SE] = -8.90 D) and hyperopic astigmatism (group B: N = 22, mean preop SE = +3.25 D) with an overall range of SE from +6.50 to -21.25 D and cylinder ranging from 1.50 to 7.50 D. Safety results were excellent at 6 months with no eye losing a line of best corrected acuity. Sixty-nine percent and 59% of myopic and hyperopic eyes, respectively, gained at least one line of best corrected acuity. Eighty-five percent and 96% of myopic and hyperopic eyes, respectively, had uncorrected acuity of 20/40 or better 6 months postoperatively. All eyes in both groups were within 1.0 D of the desired refraction at 6 months. There was a 4.5% mean endothelial cell loss during the 6-month follow-up, the majority of which

appeared at the 1 week visit. Subjective patient satisfaction was very high, with a mean rating of 9.0 out of 10.0 at 6 months. Overall, this lens may offer an excellent option to selected patients with high myopia or hyperopia with astigmatism vs bioptics, which carries with it risks associated with the flap, including epithelial ingrowth (see Chapter 18).15 Careful patient selection, including accurate measurement of anterior chamber depth (Dick et al14 recommend anterior chamber depth >3.0 mm) and pupil size (scotopic pupil ideally less than optic size), precise refraction, preoperative determination, and marking of the cylinder axis are essential for a successful result. Decentration of the lens in hyperopic eyes may be necessary, as the visual axis may not lie in the middle of the pupil.

This lens may also provide an efficacious option for the correction of phakic, postpenetrating keratoplasty ametropia with astigmatism. A recent case series of 12 eyes reports a two or more line improvement of best-corrected visual acuity in 50% of eyes.16

FOLDABLE PHAKIC

INTRAOCULAR LENSES

The major posterior chamber phakic IOLs (ie, ICL and PRL [Medennium, Irvine, Calif]) are already foldable and, as a result, may be inserted through small, clear corneal incisions (see Chapters 12 and 14). Bausch & Lomb Surgical (Rochester, NY) is testing a foldable version of the NuVita anterior chamber, angle-fixated phakic IOL.

208 Chapter 21

Figure 21-4. Artiflex flexible phakic IOL. The silicone optic flexes along its long axis and may be inserted through a 3.6-mm incision using the specially designed lens insertion system shown (courtesy of Ophtec).

Figure 21-6. ThinOptx Ultrachoice 1.0 lens optic design. The lens power is determined by the difference in curvature of the anterior and posterior surfaces. While one surface retains a continuous curvature, the second surface is lathe cut to maintain optical power while minimizing thickness. Each step or ring on the second surface has a different curvature so as to minimize spherical aberration and maintain a single focal point (courtesy of ThinOptx, Inc).

This foldable lens features an optic made of hydrogel that will go through a 3-mm incision, approximately half the size of the incision required for the current NuVita MA20 that is popular in Europe, Asia, and South America (see Chapter 15).

The Foldable Artisan

Phakic Intraocular Lens (Artiflex)

A foldable version of the major iris-fixated anterior chamber phakic IOL (the Artisan, which is to be marketed as the Verisyse in the United States [Advanced Medical Optics, Irvine, Calif]) has recently been introduced and is undergoing clinical trials in Europe. The rigid optic of the original design has been replaced by a flexible silicone optic, while the PMMA haptic design remains. The lens “flexes” along its long axis and may be inserted through a 3.6-mm incision using a specially designed insertion sys-

Figure 21-5. ThinOptx Ultrachoice 1.0 IOL. A. Packaged, rolled up form. B. Unrolled, plate form (courtesy of ThinOptx, Inc).

A.

B.

tem (Figure 21-4). Once inside the anterior chamber, the claw fixation mechanism is spread open with a double arm grasping technique or with a single arm fixation forceps.17 Early trials have shown promising results.18

ULTRATHIN INTRAOCULAR LENSES

The size of clear corneal incisions has continually decreased since the introduction of phacoemulsification. Recent advances in surgical technology, including laser and low energy, pulsed phaco techniques coupled with bimanual instruments, have allowed incision sizes to decrease below 1.5 mm. The inability to insert a lens through such a small incision, however, has limited the use of these new techniques. Several new ultrathin lenses that may provide additional options for the phakic IOL patient are now on the horizon.

ThinOptx Ultrathin Intraocular Lenses

The Ultrachoice 1.0 lens (ThinOptx, Abingdon, Va), manufactured using nano-scale precision technology, is an ultrathin, rollable IOL with dioptric powers ranging from -25 D to +30 D in 0.125 D increments and lens thickness ranging from 30 to 350 m, depending on dioptric power (Figure 21-5). The posterior surface of the optic is one continuous curve, while the anterior surface is lathe cut with a series of steps, 50 m in height, in a concentric pattern (Figure 21-6). This design allows the lens to remain extremely thin, even with large dioptric powers. Unlike a Fresnel lens, in which each concentric section has a different focal point, each concentric section in the Ultrachoice 1.0 has a different radius of curvature to create one focal point for the entire lens, thus reducing spherical aberration (Figure 21-7). The lens may be inserted through a 1.5-mm incision in a rolled configuration (Figure 21-8). The lens then unrolls into a posteriorly vaulted plate configuration

Figure 21-7. Ultrachoice 1.0 thin lens is not a Fresnel lens. A Fresnel lens (left) has multiple focal points. The Ultrachoice lens is designed such that all light rays focus at a single point (courtesy of ThinOptx, Inc).

Figure 21-9. Ultrachoice 1.0 thin lens in-vivo configuration. A. The lens unfolds in the capsular bag into a plate configuration. B. Eyelets in the plate haptic should point in a clockwise direction, ensuring

A. proper front/back orientation. In-vivo, the lens rests in a posterior vaulted orientation as shown (courtesy of ThinOptx, Inc).

B.

and fixates in the capsular bag (Figure 21-9). ThinOptx has also developed an anterior chamber, angle-fixated phakic version of the Ultrachoice 1.0 featuring the same type of ultrathin optic (Figure 21-10). A high-resolution ultrasound shows the position of the phakic IOL relative to the corneal endothelium and natural lens (Figure 2111). Eight implants have been placed with good efficacy and safety to date.19

The Future of Phakic Intraocular Lenses 209

Figure 21-8. Implantation of the Ultrachoice 1.0 Thin lens. A. The lens is inserted in rolled up form through a sub- 2.0-mm clear corneal incision. B. The lens is inserted into the capsular bag (courtesy of

A. ThinOptx, Inc).

B.

Figure 21-10. ThinOptx angle-supported anterior chamber phakic IOL (courtesy of ThinOptx, Inc).

The Vision Membrane

This 200- m thick, angle-fixated, anterior chamber lens (Vision Membrane Technologies, Carlsbad, Calif) makes use of diffractive optics to correct myopia from - 2.00 to -15.00 D and hyperopia from +2.00 to +6.00 D. The foldable lens may be implanted through a sub-2.0 mm incision. In addition to its extremely thin design, which may offer advantages with regard to endothelial cell loss, intraocular inflammation, and cataract formation, the lens features a large 6.5-mm optic. Particularly with myopic patients, this large optic size may be more forgiving relative to decentration and subsequent aberrations with large