Intraocular lenses

Published on 08/03/2015 by admin

Filed under Opthalmology

Last modified 08/03/2015

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CHAPTER 15 Intraocular lenses

Materials for lens implant manufacture

The original material was polymethyl methacrylate, chosen because it was found to remain in the eye without causing inflammation (as evidenced by fragments of the shattered windshield from Spitfire fighter planes lodging in the pilot’s eyes), but its principal failing was that it was not foldable.

Silicone was used because it was foldable, and various designs including three-piece with central silicone optic and PMMA haptics, or plate haptic in a one-piece design were developed. They suffered from the problem of greater postoperative inflammation, although this is not an issue with the second generation silicone lenses. The plate haptic designs were relatively unstable and were associated with posterior capsule opacification.

The most popular material used today is an acrylic material which is divided into hydrophilic and hydrophobic variants. These lenses are usually one piece, but can be a three-piece with PMMA haptics. The advantage of this material is better biocompatibility, reduced posterior capsular opacification, and the ability to modify the surfaces to provide toric, aspheric, and multifocal and bifocal intraocular lens implants.

A further development has been the light adjustable lens, in which the surface and shape of the lens can be modified postoperatively to fine tune the refraction and optical properties of the lens, and then fixed using UV light.

There have also been problems with lens implants with the hydrogel lenses causing opacification/calcification (Fig. 15.1) and glistenings/trapped fluid in vacuoles occurring in the hydrophobic acrylic lenses although these do not seem to cause visual symptoms2,3.