Abstract
Abstract: :
Purpose:We previously found that foveal scotopic dark adaptation occurs within a few minutes in young subjects. The present study was conducted in order to measure and compare scotopic foveal contrast sensitivity in younger and older subjects. Methods:Twenty two Subjects with BCVA of 20/30 or better were divided into 2 age groups (19–50 and 51–76 years). The older group patients were all pseudophakic with clear refractive media. All patients had otherwise normal ophthalmic examination. Scotopic contrast sensitivity (CS) was tested by a computerized algorithm using adaptive method (staircase) and two temporal alternatives forced–choice for target's detection that estimated the contrast threshold at the 79% level. The targets were Gabor patches with spatial frequencies of 1.5, 2.25, 3, and 6 cpd. The test was conducted in a completely darkened room, and the monitor was covered with a dark filter that allowed luminance of only 1 cd/m2 (The mean luminance of the monitor was 40 cd/m2. It was gamma corrected to achieve linear range). The testing started after 3 minutes of dark adaptation and lasted about 15 minutes. Results:The measurement was easily performed by subjects of all ages. In the two patients groups the scotopic CS was higher for 1.5 cpd and decreased with increasing spatial frequencies, while at 6 cpd most of the subjects were unable to detect the target. However, the CS of the younger group was higher by about a factor of two than the older group. Conclusions:Foveal scotopic CS decline with age, an effect that can be measured by a simple rapid and computerized test. Bearing in mind that the subject’s ocular media was completely clear, the study supports the hypothesis that the decline in scotopic contrast sensitivity with aging involves neuronal changes in the visual processing.
Keywords: contrast sensitivity • aging • neuro–ophthalmology: cortical function/rehabilitation