SOFT CONTACT LENSES AND CHEMICAL VAPORS: IS AMMONIA ABSORBED BY HIGH WATER CONTENT HYDROGEL LENSES

James LaMotte

Abstract

Warnings against wearing soft contact lenses in enviornments with chemical vapors have been issued for many years. These warnings seem to be based mostly on speculation, as few studies have been done on the absorption and release of chemical vapors by soft lenses. The purpose of our study was to determine if a high water content lens would absorb vapors from ammonia. Despite the fact ammonia is a common household, laboratory and industrial chemical we found no studies on the interaction of ammonia with soft contact lenses. Ten high water content lenses (Acuvue-etafilcon 58% ) were exposed to different concentrations of ammonia vapor generated in a cuvette by a drop of aqueous ammonia. The concentration of ammonia in the cuvette was varied by changing the size of drop introduced into the cuvette and measured by a spectrophotometer during a 5 minute exposure. After exposure to the vapor the contact was quickly transferred to a 0.9% saline solution containing an colorometric indicator for ammonia and the amount of ammonia released into the saline was measured with the spectrophotometer. We found that significant quantities of ammonia were absorbed into the lenses. The relationship between average concentration of ammonia vapor exposure and amount absorbed per contact lens was nearly linear from 50 parts per million (ppm) to 250 ppm ammonia vapor. For concentrations greater than 250 ppm there appears to be a saturation effect in these contact lenses. Our findings indicate that high water contact lenses will absorb ammonia and release it into a solution similar to tears. We intend to study other chemical vapors and lenses with various water contents.

Details

Year: 1993

Program Number: Poster 8

Resource Type: Scientific Program

Author Affiliation: n/a

Co-Authors: Greg Smith, Ana Chang-Smith

Co-Author Affiliation: n/a

Room: Exhibit Hall