OPTICAL-DENSITY OF THE HUMAN LENS

Optic disk reflectance was measured from 27 normal observers with thei r physiological lenses (aged 21-74 yr) and from two pseudophakic obser vers (aged 69 and 70 yr) with use of a Utrecht fundus reflection densi tometer. Psychophysical heterochromatic flicker photometric luminance matches (10 degrees field) were obtained on the same group of the obse rvers. A four-parameter model incorporating lens density, hemoglobin a bsorption, optic disk reflectance, and superficial stray light was use d to fit the reflectometric data. A model incorporating lens density a nd the Judd revised spectral luminous-efficiency function was used to fit the psychophysical data. The lens-density spectrum used the two-fa ctor aging model of Pokorny, et al. [Appl. Opt. 26, 1437 (1987)]. The lens density for each normal observer was estimated through a least-sq uares fitting procedure yielding an estimated lens age. For the reflec tometric data the observer's chronological age agreed with estimated l ens age with a correlation coefficient of 0.92. The reflectometric reg ression line underestimated chronological age by approximately 5 yr. T he mean reflectance of the optic disk was 0.047 with standard error of the mean of 0.0044. Data from the pseudophakic observers were well de scribed when corneal density was used to replace lens density. The len s density was also estimated from the psychophysical data. The observe r's chronological age agreed with psychophysically estimated lens age with a correlation coefficient of 0.92. It was concluded that the in v ivo lens density can be estimated from the reflectance spectrum measur ed off the optic disk. The reflectance spectrum of the optic disk was inferred to be close to spectrally neutral. (C) 1997 Optical Society o f America.