Intraocular lens materials and styles: A review

A number of commercially available polyimide materials were evaluated in vitro using a selected battery of levels I and II testing protocols prescribed by the National Institutes of Health Guidelines for Blood-Material Interactions. These procedures consisted of electron spectroscopy for chemical analysis and contact angle characterization surface studies, and protein adsorption, cell culture cytotoxicity, clotting time and haemolysis biocompatibility testing. The polyimide surfaces were invariant from the bulk composition with 60-80% C, 10-20% O and 2-5% N, producing advancing contact angles in the hydrophobic range (80-100 degrees). Consequently, they adsorbed significant amounts of albumin (2-3 micrograms/cm2) and fibrinogen (0.5-0.8 microgram/cm2). The polyimides also displayed an insignificant level of cytotoxicity and haemolysis, and clotting times ranged from 63 to 98% of normal. These clotting times and haemolytic index values were intermediate between the values observed for Teflon and Silastic controls. These factors, along with the strong adherence of polyimides to metal oxide substrates, indicate that polyimide materials are good candidates for further testing as encapsulants for implantable biosensors.

A series of 897 Nd:YAG laser posterior capsulotomies were reviewed for the complications of cystoid macular edema, retinal detachment, new onset of glaucoma, and worsened preexisting glaucoma. After Nd:YAG capsulotomy, 11 patients (1.23%; 95% confidence interval, 0.51% to 1.95%) developed cystoid macular edema and eight patients (0.89%; 95% confidence interval, 0.28% to 1.5%) developed a retinal detachment. The new onset of glaucoma was observed in seven patients (0.78%; 95% confidence interval, 0.20% to 1.36%). Five patients (0.56%; 95% confidence interval, 0.07% to 1.05%) with preexisting glaucoma had persistent worsening of their glaucoma. Most patients with a complication had no identifiable risk factors in common. The numbers of laser pulses and energy delivered were not risk factors. Retinal detachment and cystoid macular edema developed most often many months after capsulotomy and many months to years after the cataract surgery. Patients undergoing Nd:YAG laser capsulotomy therefore require ongoing medical observation to detect and treat these serious complications.

Silicone breast implants have been linked to a variety of illnesses, the most controversial of which are connective-tissue diseases and symptoms. To study this relation, we analyzed data from 14 years of follow-up of the Nurses' Health Study cohort. Women who were free from connective-tissue disease in June 1976 were followed through May 31, 1990, before there was widespread media coverage of the possible association of breast implants and connective-tissue diseases. Information was collected through biennial and supplementary mailed questionnaires and blinded reviews of medical records with the use of standardized criteria. Relative risk, the measure of association, was defined as the incidence rate of connective-tissue disease among women with breast implants divided by the corresponding incidence rate among women without breast implants. Among 87,501 women who were eligible for follow-up, 516 were confirmed as having definite connective-tissue diseases and 1183 as having breast implants (of which 876 were silicone-gel-filled, 170 saline-filled, 67 double-lumen, 14 polyurethane-coated, and 56 of unknown type). The mean (+/- SD) period of follow-up after surgery was 9.9 +/- 6.4 years (range, 1 month to 40.5 years). Three of the patients with definite connective-tissue disease--all had rheumatoid arthritis--had implants (one silicone-gel-filled, one saline-filled, and one double-lumen). The age-adjusted relative risk of a definite connective-tissue disease among women with any type of implant was 0.6 (95 percent confidence interval, 0.2 to 2.0), as compared with women without implants. For women with silicon-gel-filled implants, the comparable relative risk was 0.3 (95 percent confidence interval, 0 to 1.9). The relative risk of self-reported signs or symptoms of connective-tissue disease for women with implants was 1.5 (95 percent confidence interval, 0.9 to 2.4); the risk of having any 1 of 41 signs, symptoms, or laboratory features of connective-tissue disease was 0.7 (95 percent confidence interval, 0.3 to 1.6). In a large cohort study, we did not find an association between silicone breast implants and connective-tissue diseases, defined according to a variety of standardized criteria, or signs and symptoms of these diseases.