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L. T. Chylack Jr, A. H. Feiveson, L. E. Peterson, M. L. Wear, W. H. Tung, F. K. Manuel, L. J. Marak, F. A. Cucinotta; NASA Study of Cataract in Astronauts (NASCA): Analysis 2-3 Years of Data. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2135.
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Continuous measures of C, N, and P were derived from Nidek EAS 1000 digitized images. Age, demographics, general health, nutritional intake, solar ocular exposure, and other confounding variables were measured at baseline and annually. Non-parametric analyses in which multiple slopes describing cataract progression rates for all possible pairs of repeated measurements of each eye within each subject were tabulated. Preprocessing consisted of adjusting all opacities for differences in initial age of observation, nutritional intake, sun exposure, and tobacco use. Point estimates and confidence intervals (CIs) were obtained for Somers D, the probability of increase minus the probability of decrease given some change has occurred. Total radiation exposure levels and galactic cosmic ray (GCR) doses were grouped into 5 levels: 0, and approximate quartiles of lens dose.
Estimates of mean % growth/yr were 4.9 and 5.6 for C and N opacities, respectively. The growth/yr for PSC could not be estimated due to the large number of zeros.Estimated probabilities and (95% CIs) for the difference between concordance (i.e., increase with time) and discordance (decrease with time) for randomly selected slope pairs were 0.12 (0.06, 0.19), 0.02 (-0.06, +0.09), and 0.52 (0.46, 0.58) for C, P, and N, respectively, for all subjects and radiation exposures. N mask density was the most sensitive (and area opaque C the next most sensitive) to the passage of time. Measures of P were highly skewed with many zeros or very low values that for many subjects did not change. There was no increase in Somers’ D with radiation level, (either overall or GCR). All analyses were adjusted for 16 nutrients (adjusted for total caloric intake), so effect of individual nutrients on progression could not be ascertained.
It is probable that the effect, if any, of space radiation exposure on progression of lens opacification will be discernable after more than 2-3 years of observation. Our original goal of at least 5-yrs of follow-up likely will be needed.
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