Ординатура / Офтальмология / Английские материалы / Modern Cataract Surgery_Kohnen_2002

use a self-sealing scleral-tunnel incision in these cases, but if the anterior chamber is a normal size, a clear-corneal incision is possible. If PMMA lenses are used, then a scleral-tunnel incision is necessary, as the incision length must accommodate the 5.5-mm optic, and a 5.5-mm clear-corneal incision would have an increased risk of infection. If we are able to perform a clear-corneal incision, we use a 2.5-mm incision length and implant the silicone IOLs.

The incision is placed in the steep meridian to correct pre-existing astigmatism. In some cases limbal or corneal relaxing incisions are also performed to correct pre-existing astigmatism [8]. One IOL is bag fixated with the secondary IOL in the sulcus to prevent interlenticular opacification that can be seen with both IOLs bag fixated.

Phacoemulsification is more challenging in a short eye. One of the challenges that may arise during phacoemulsification is pupillary block. Increased IOP from choroidal effusion or fluid misdirection is more common in hyperopic eyes and can cause a progressive shallowing of the anterior chamber as the eye hardens. Short eyes are at greater risk for expulsive hemorrhage. Another complication associated with a short eye is iris prolapse when the phaco tip is inserted.

Secondary Piggyback Implantation for Overor

Underpowered Pseudophakes

If the patient is pseudophakic and underor overpowered in the contralateral eye, a second IOL can be implanted under topical anesthesia to provide the needed corrective power. There is no need for a removal/exchange, which would be traumatic and increases the risk for retinal tears, cystoid macular edema, and cyclodialysis, and is associated with posterior or anterior capsule rupture, decreasing capsular support. Also, since the original IOL is fixed, there is no concern over the possibility that the IOL will change position as can happen after an exchange and there is no need to determine why the power is wrong (calculation mistake, IOL power incorrectly marked, etc.).

The necessary corrective power is provided by implanting a second IOL of appropriate power with haptics fixated in the sulcus. Underpowered cases can have a low-power lens implanted, while in overpowered cases, a minus-powered lens can be used. The refraction is used to determine the power requirement. For secondary piggyback implantation, we use the Holladay II software for calculating the power; however, we have found that for overpowered pseudophakes, the appropriate IOL is approximately equal in power to the spherical equivalent.

Table 1. Our lens choices for secondary piggybacks

Underpowered pseudophakes lenses

STAAR AQ5010

Silicone, convex/plano, 6.3-mm optic, three-piece IOL Diopter range: plano to 4 (1-D steps)

STAAR AQ2010V

Silicone, biconvex, 6.3-mm optic, three-piece IOL

Diopter range: 5 to 9 (1-D steps); 9.5 to 30.5 (0.5-D steps) Storz P547UV

PMMA, equiconvex, 6.0-mm optic, sulcus, one-piece IOL Diopter range: plano to 34.0 (0.5-D steps)

Storz P359UV

PMMA, equiconvex, 5.5-mm optic, one-piece IOL Diopter range: plano to 45 (0.5-D steps)

Overpowered pseudophakes lenses

STAAR AQ5010

Silicone, convex/plano, 6.3-mm optic, three-piece IOL

Diopter range: –1.0 to –4.0 (1-D steps)

Storz P547 UV

PMMA, equiconvex, 6.0-mm optic, one-piece IOL

Diopter range: 1.0 to 18.0 (1-D steps)

Our lens choices for secondary cases are presented in table 1. The availability of the STAAR AQ5010 silicone IOL in low-powered and minus-powered lenses allows for secondary piggyback implantation through a 2.5-mm clearcorneal incision.

Intralenticular Opacification

Intralenticular opacification (ILO), a long-term complication of piggyback lenses has recently been reported [14–17]. ILO is cellular growth between piggybacked lenses, which is often characterized as Elschnig pearl formation, and may even result in a fibrous membrane formation between the lenses. Interlenticular opacification has been reported primarily in acrylic lenses with long-term follow-up, although it has also been seen in PMMA and silicone piggybacks [14–17].

Gayton [17] has reported an incidence of ILO of 43% among his acrylic piggybacks and 22% among his PMMA piggybacks. He has reported a number of cases with thick, opaque membranes that have severely impacted vision and

Fig. 2. Interlenticular opacification, or cellular ingrowth into the piggyback lens interface.

required surgical removal. Moreover, both Gayton [17] and Shugar [15] have reported a shift in refraction among cases with significant ILO.

We conducted a study of all our piggyback cases with at least 2-year possible follow-up and examined them at slit lamp to determine the extent of the problem in our practice. We examined 50 eyes of 34 patients, 22 eyes with piggybacked PMMA lenses, 19 with silicone, and 9 with one PMMA and one silicone lens. We found 3 eyes, or 6%, showed signs of ILO, 2 with piggybacked PMMA (fig. 2) and 1 with mixed PMMA and silicone. In these 3 cases, we saw only mild interface growth, with no impact on visual function, no shift in refraction, and no symptoms of glare or shadows. We found no cases of ILO in double-silicone piggybacks, even with both in the bag.

We found a much lower incidence and severity of ILO in our practice than reported by Gayton or Shugar, which may be due either to a difference in IOL material, since we do not use acrylic, or to a difference in surgical technique. Dr. Apple [14, 17] has implicated incomplete removal of epithelial cells as a possible cause of ILO. Since we routinely polish the capsule in all our cataract cases (fig. 3), we effect a more complete removal of lens epithelial cells at surgery, which may have significantly lowered our incidence of ILO.

While we believe that polishing the capsule is an important step for all cataract cases, meticulous attention to removal of all epithelial cells is especially crucial in piggyback cases. While the causes of this complication are not yet

Fig. 3. Polishing the capsule removes more lens epithelial cells and may reduce the incidence of interlenticular opacification.

well understood, and methods of treatment still under study, a careful polishing of the capsule and removal of all lens epithelial cells may significantly lower the incidence and severity of the problem.

References

1Gayton JL, Sanders VN: Implanting two posterior chamber intraocular lenses in a case of microphthalmos. J Cataract Refract Surg 1993;19:776–777.

2Gayton JL, Raanan MG: Reducing refractive error in high hyperopes with double implants; in Gayton JL (ed): Maximizing Results. Thorofare, Slack Inc, 1996, pp 139–148.

3Gills JP, Gayton JL, Raanan MG: Multiple intraocular lens implantation; in Gills JP, Fenzl R, Martin RG (eds): Cataract Surgery: State of the Art. Thorofare, Slack Inc, 1998.

4Shugar JK, Lewis C, Lee A: Implantation of multiple foldable acrylic posterior chamber lenses in the capsular bag for high hyperopia. J Cataract Refract Surg 1996;22:1368–1372.

5Gills JP: The implantation of multiple intraocular lenses to optimize visual results in hyperopic cataract patients and under-powered pseudophakes. Best Papers of Sessions, 1995 Symposium on Cataract IOL and Refractive Surgery Special Issue, 1996.

6Gills JP, Fenzl RE: Minus power intraocular lenses to correct refractive error in myopic pseudophakia. J Cataract Refract Surg 1999;25:1205–1208.

7Gayton JL, Sanders V, Van Der Karr M, Raanan MG: Piggybacking intraocular implants to correct pseudophakic refractive error. Ophthalmology 1999;1066:56–59.

8Holladay JR: Achieving emmetropia in extremely short eyes. Annual Meeting of the American Academy of Ophthalmology, Chicago 1996.

9Holladay JR, Gills JP, Leidlein JL, Cherchio M: Achieving emmetropia in extremely short eyes with two piggyback posterior chamber intraocular lenses. Ophthalmology 1996;103:1118–1123.

10Sanders DR, Retzlaff JA, Kraff MC: A-scan biometry and IOL implant power calculations; in Focal Points: Clinical Modules for Ophthalmologists. San Francisco, American Academy of Ophthalmology, 1995, vol 13, pp 1–14.

11Holladay JT, Prager TC, Ruiz RS, Lewis JW: Improving the predictability of intraocular lens power calculations. Arch Ophthalmol 1986;104:539–541.

12Shammus HJF: A comparison of immersion and contact techniques for axial length measurement. Am Intraocular Implant Soc J 1984;10:444.

13Fenzl RE, Gills JP, Cherchio M: Refractive and visual outcome of hyperopic cataract cases operated on before and after implementation of the Holladay II formula. Ophthalmology 1998; 105:1759–1764.

14Gayton JL, Apple DJ, Peng Q, Visessook N, Sanders V, Werner L, Pandey SK, Escobar-Gomez M, Hoddinott DS, Van Der Karr M: Interlenticular opacification: Clinicopathological correlation of a complication of piggyback posterior chamber intraocular lenses. J Cataract Refract Surg 2000;26: 330–306.

15Shugar JK, Schwartz T: Interpseudophakos Elschnig pearls associated with late hyperopic shift: A complication of piggyback posterior chamber intraocular lens implantation. J Cataract Refract Surg 1999;25:863–867.

16Shugar JK, Keeler S: Interpseudophakos intraocular lens surface opacification as a late complication of piggyback acrylic posterior chamber lens implantation. J Cataract Refract Surg 2000;26: 448–455.

17Gayton JL, Apple DJ, Van Der Karr M, Sanders V: Refractive stability and long-term interlenticular membrane formation of piggybacked intraocular implants. J Cataract Refract Surg 2001 (in press).

Dr. James P. Gills, St. Luke’s Cataract and Laser Institute, 43309 US Highway 19N, PO Box 5000, Tarpon Springs, FL 34688 (USA)

Tel. 1 727 938 2020, Fax 1 727 938 5606, E-Mail drgills@stlukeseye.com

Multifocal IOLs were designed to improve near and intermediate vision without supplementary glasses, as well as provide distance vision, because they can produce a variable number of foci, either finite or infinite, depending on the lens design. A cortical elaboration process is believed to enable the subject to choose the image most clearly in focus [1]. This phenomenon is called ‘pseudoaccommodation’ and may depend in part on the Stiles-Crawford effect. Since multifocal IOLs always produce an in-focus and an out-of-focus image, and visual processing allows partial or total suppression of the out-of-focus image, it is not surprising that some subjects are aware of the ‘blur circles’, which are colloquially referred to as ‘haloes’.

In this chapter, we review the designs and effectiveness of various marketed and investigational multifocal IOLs.

History of Multifocal IOL Development

Designs

Multifocal IOLs are based on either refractive or diffractive optics and differ in design and material (table 1) [2]. All refractive IOLs use the total available light without losing any to higher order diffraction. The Array multifocal IOL (Allergan Surgical, Irvine, Calif., USA) and Domilens Progress 1 (Domilens, Lyons, France) are refractive designs that obtain multifocality from a change in optical refractive power in different areas of the IOL optic. This allows the lens to focus images from various distances onto the retina. The Array is a foldable, concentric, zonal-progressive design, with a series of repeatable, continual aspheric power distributions on the anterior surface of the lens (fig. 1a,b) [3]. It is distance-dominant and, therefore, appropriate for a distance-vision-dominant species. In an eye with an average pupil size, approximately 50% of incoming light is allocated to distance focus, 13% to the intermediate range, and 37% to the near image [2].

The Domilens Progress 1 is a one-piece, progressive, PMMA IOL. The Progress 1 optics are aspheric biconvex, with light allocated predominantly to the near image [4].

True Vista is a three-zone refractive bifocal IOL (designed by Storz Instrument Co., St. Louis, Mo., USA, and acquired by Bausch & Lomb Surgical, Claremont, Calif., USA). The biconvex IOL has a central (distance) zone, near annulus, and peripheral (distance) zone. The near annulus has an add power of 4 D [5].

Diffractive IOLs include the CeeOn 811E and Pharmacia 808X (Pharmacia Upjohn, Kalamazoo, Mich., USA), and 3M 825X and 815LE (designed by 3M,

Table 1. Designs of multifocal IOLs (adapted from Steinert [2])

Minneapolis, Minn., USA and rights acquired by Alcon, Fort Worth, Tex., USA). Diffractive IOLs use a modified phase plate that creates constructive interference of light rays, thereby directing light to discrete near and far foci [3]. As a result of this design, most diffractive IOLs are bifocal. For most diffractive IOLs, approximately 41% of incoming light is allocated for distance and 41% for near vision. The remaining 18% of light cannot be focussed because it is lost to higher order diffraction, forming images that can never be visualized because they do not reach the retina.

Fig. 1. Array refractive multifocal IOL (Allergan Surgical). a Schematic of zonalprogressive lens design. b Photograph depicting aspheric rings on anterior surface (from Steinert et al. [3]).

The following studies use Snellen, Snellen equivalent, or the decimal scale. The decimal scale ranges from 0.05, or 20/400 Snellen, to 1.0, or 20/20 Snellen.

Effectiveness

The effectiveness of multifocal IOLs can be measured in terms of distance visual acuity, near visual acuity, depth of focus, contrast sensitivity, visual symptoms, driving ability, independence from spectacles, subject satisfaction, and quality of life. The multifocal IOL reported on most often in the literature is the Array. It has been studied in comparisons with monofocal IOLs [3, 6–12], the Domilens Progress 1 refractive multifocal IOL [13], the CeeOn 811E [13, 14] and 3M diffractive bifocal IOLs [15–17] and a PMMA bifocal IOL from Bausch & Lomb [18] (table 2). The CeeOn 811E diffractive bifocal IOL was studied in a noncomparative trial [19], and the True Vista refractive bifocal IOL in several comparative and noncomparative trials [5, 20–22]. An investigational diffractive bifocal IOL, Pharmacia model 808X, was studied in comparative trials with a monofocal IOL of similar design [23, 24].

Distance Visual Acuity

The effectiveness of monofocal IOLs on distance visual acuity is well characterized. The effectiveness of multifocal and bifocal IOLs on distance visual acuity has been measured in several clinical trials.

Steinert et al. [3] evaluated the safety and effectiveness of the Array in a prospective, nonrandomized, multicenter, fellow eye comparative trial in the USA (n 456). All subjects were implanted with the Array. The fellow eye was either phakic or implanted with a multifocal or monofocal IOL. At five of the sites, subjects participated in a paired-eye comparison trial, with an Array model SA40 in one eye and a PhacoFlex II model SI40NB silicone IOL (Allergan Surgical) in the fellow eye (n 102). In this study, mean uncorrected (i.e. without spectacles) distance visual acuities at 1 year were 20/32 (Snellen) for the multifocal and 20/30 for the monofocal IOL. Uncorrected distance visual acuity of 20/20 or better was achieved by 18% (18 of 102) eyes with the multifocal IOL, and by 30% (31 of 102) eyes with the monofocal IOL (fig. 2). The mean best-corrected distance visual acuities were 20/25 for eyes with the multifocal IOL and 20/23 for those with the monofocal IOL, with a mean difference between eyes of 0.3 line (Snellen equivalent) (p 0.002). Bestcorrected distance visual acuity of 20/20 or better was achieved by 49% (50 of 102) of eyes with the multifocal and by 59% (60 of 102) of eyes with the monofocal IOLs ( p 0.002).

Javitt and Steinert [12] measured visual function and quality-of-life outcomes in subjects implanted bilaterally with the Array multifocal IOL (n 127)