Light adaptation in letter contrast sensitivity: The influence of optical and neural mechanisms

Abstract

This work discusses the relative significance of optical and neural mechanisms in letter contrast sensitivity under different conditions of environmental lighting. A study was carried out on 26 eyes with normal ocular health. Sixteen lighting conditions were obtained by combining different test luminances (from 10 cd/m2 to 600 cd/m2) and surround luminances (from 1 cd/m2 to 600 cd/m2). The results reveal a significant influence of optical factors (pupil size variations and glare effects) on contrast sensitivity when surround luminance changes, and a dominance of neural effects when test luminance changes. Furthermore, test size and illumination conditions are identified for which letter threshold contrasts are not sensitive to surround luminance changes.

Functional outcomes after combined iris and intraocular lens implantation in various iris and lens defects

“…Compared to normal controls, visual performance of injured eyes appears to be worse in terms of low contrast conditions [ 19 ]. Since glare effects and pupil size deviations are crucial factors for the reduction of contrast sensitivity [ 20 ], the results in our patients were below the age-related standard contrast sensitivity values in normal persons [ 21 , 22 ] because of significant traumatic iris tissue loss. In general, postoperative contrast sensitivity improved at photopic and mesopic luminance levels, although this tendency was not statistically significant in mesopic conditions but in photopic.…”