Visual property of people with low vision (2): contrast sensitivity function

摘要

In order to establish vision data of low vision to be used for better lighting and signing for them, contrast sensitivity function (CSF) of people with low vision was measured for a number of people who have impaired vision due to various types of pathological disorders in visual pathways. Contrast sensitivity function was measured by presenting a sine wave grating pattern on a CRT display with variable frequency and variable contrast to obtain a threshold point for detection of the grating pattern. It was found that the sensitivity of low vision varied widely from the level of almost near to normal younger people to far lower to that. The sensitivity loss of low vision was prominent at higher frequency region above about 1 cycle per degree (cpd). Consequently the function had a maximum sensitivity at around 0.3 cpd in average. These data suggests that much care should be taken to avoid using high frequency components in designing visual signs for low vision.