INTRAOCULAR LENSES - NEW BIOMATERIALS FOR SMALL-INCISION CATARACT-SURGERY

In 1949, Harold Ridley implanted the first intraocular lens, after cat aract surgery, he had chosen as the best available material Polymethyl Metacrylate noticing during the war in the injured eyes of the R.A.F Pilots that the material was perfectly tolerated inside the eye as a f oreign body. It took 10 years for intraocular lenses to take off, due to the necessary improvement of both surgery and manufacturing, since then all the intraocular lenses are made of the same material and perf ectly tolerated. However the material is hard and not foldable. The im provement of Phakoemulsification have made small incision (3,2 mm) sur gery possible, however there is a need for new foldable implants that can be inserted into the eye through a small incision, so rather new b io material are now being used. A variety of silicone foldable lenses have been proposed, their advantages are : easy foldability, solidity and injectability through an injector. Their disadvantages are, as com pared to the 40 years standing solid PMMA lenses; less biocompatibilit y changes in color and apparition of crystal precipitates. Also report s on induced polyarthritis, lupus and paraneoplasic syndroms with othe r silicone prosthesis, these complications appear after 5 or 6 years. Although new silicone lenses are being brought on the market, there is some hesitation in implanting these lenses on patients less than 80 y ears of age. Polyhema lenses appeared in 1985, with 38 % water content . The material is perfectly biocompatible even more than PMMA, however their initial design mi was not adequate until 1992. Their advantages are perfect biocompatibility over the years, autoclavability. Their o nly disadvantage a certain fragility during folding. Our 7 years exper ience with silicone and hydrogel has shown that 20 % of the first sili cone lenses had to be exchanged between 3 to 4 years after surgery and 0 % of the polyhema. Posterior capsule opacification at 1 year was tw ice more frequent with silicone thant with PMMA or hydrogels and that mild chronic uveitis occurs 3 times frequently with silicone lenses.