Foldable intraocular lenses and vitreoretinal surgery

Abstract

Phacoemulsification is now practiced throughout the world. In recent years, the advances in small incision techniques have been paralleled by the development of foldable intraocular lenses (IOLs) that can be implanted through these small incisions. The popularity of foldable IOLs has grown. These lenses are preferred by 17 to 20% of the respondents to the 1996 survey of members of the American Society of Cataract and Refractive Surgery.l Because of the relative ease of implanting foldable lenses, many ophthalmologists select them for all their patients. There are circumstances, however, in which alternatives to foldable IOLs might be considered. Several authors4 have reported that in patients with exfoliation syndrome, high myopia, and pars planitis, there is a higher incidence of capsule contraction and IOL decentration with foldable lenses. In these situations, one-piece poly(methyl methacrylate) (PMMA) lenses appear to be more efficacious. In this issue, Apple et al. describe the IOL surface characteristics that influence silicone oil adherence. An earlier study5 reported the complication of irreversible silicone oil adhesion to foldable silicone IOLs during vitreoretinal surgery. Although this is a rare complication, the greater use of foldable lenses might increase the population at risk. In another experimental study,6 retinal image degradation related to condensation on the IOL after phacoemulsification, vitrectomy, and fluid-air exchange in the rabbit eye was greater with the silicone IOL than with the PMMA or the acrylic IOL. The condensate is readily removed from the latter lens materials but not from silicone. The present study assesses the wettability of the 10 L surface, which influences silicone oil adhesion. While the silicone IOL surface was associated with the greatest degree of silicone oil adherence, acrylic lenses and the MemoryLens also showed a significant amount of oil coverage compared with the human lens capsule. Conventional PMMA, hydrogel, fluorine-treated PMMA, and heparin-surf ace-modified PMMA were not associated with significant silicone oil adherence. The message of these findings is that a confluence of circumstances, often temporally disparate, may affect an outcome. Certain eyes are more likely to develop conditions that might result in the need for vitreoretinal procedures. In these eyes, the choice of an IOL is important and will often precede the requirement for posterior segment surgery. Selecting an appropriate IOL to satisfy the functional needs of our patients might also positively influence the outcome of a subsequent vitreoretinal procedure. The surgical flexibility afforded by phacoemulsification need not be invariably linked to the implantation of a flexible IOL. The silicone oil story is an important lesson.