Cigarette smoking and the risk of development of lens opacities. The Framingham studies.

OBJECTIVE: To examine the association between cigarette smoking and the incidence of nuclear and non-nuclear lens opacities in members of the Framingham Eye Study Cohort. PARTICIPANTS AND METHODS: Eye examinations were conducted on surviving members of the Framingham Heart Study Cohort from 1973 to 1975 (Framingham Eye Study I) and again from 1986 to 1989 (Framingham Eye Study II). Smoking data, collected biennially since 1948 in the Heart Study, were used to examine the relationship between cigarette smoking and the incidence of lens opacities. Two thousand six hundred seventy-five persons were examined in the Framingham Eye Study I. Our analysis included 660 persons, aged 52 to 80 years, who were free of lens opacities at the first eye examination. RESULTS: During the approximately 12.5 years between eye examinations, lens opacities developed in a total of 381 persons, with nuclear opacities constituting the most frequent type. In logistic regression analyses that controlled for age, sex, education, and diabetes, a significant positive association with increasing duration of smoking and number of cigarettes smoked daily was found for nuclear lens opacities, alone or in combination (test for trend, P < or = .002), but not for nonnuclear opacities (test for trend, P = .62). Among the heavier smokers (persons who smoked > or = 20 cigarettes per day according to 6 or more biennial Framingham Heart Study examinations), 77% were still smoking at the time of the first eye examination. Persons who smoked 20 or more cigarettes per day at the time of the first eye examination were at substantially increased risk for the development of nuclear opacities than nonsmokers (odds ratio, 2.84; 95% confidence interval, 1.46-5.51). There was no apparent excess risk for persons with nonnuclear lens opacities (odds ratio, 1.42; 95% confidence interval, 0.65-3.07). CONCLUSION: This study provides further evidence that cigarette smokers have an increased risk of developing nuclear lens opacities. The risk was greatest for heavier smokers, who tended to be current smokers and who smoked more cigarettes and for a longer duration.

Aerobic responses of the cornea to isopropyl alcohol, measured in vivo.

With the use of a micropolarographic system, the effects of a series of isopropyl alcohol concentrations on oxygen uptake by the corneal epithelium of the rabbit were measured in vivo. Based on an exposure period of 10 sec, followed by a saline rinse, concentrations of greater than 31% were found to cause an abrupt and severe decline in oxygen uptake, with oxygen flux responses associated with 44% and greater being indistinguishable 60 min later from those of an epithelially denuded cornea. Initial flux variations, e.g. a mild depression at 24% and a mild elevation at just under 31%, were still evident 1 h following exposure. A slope model for estimating that concentration, the aerobic reduction dosage, which would reduce the oxygen flux activity of the epithelium to half, called here the ARD50, was found for this exposure time to be 37%. That estimate is in very close agreement with measured responses. A susceptibility ratio (SR), for comparing the relative toxicities of different agents based on the quotient of their ARD50 values, was calculated here for sodium hydroxide and isopropyl alcohol, and found to be 50:1.