Assessment of contrast sensitivity of patients with macular disease using reduced contrast near visual acuity charts

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Abstract
A set of near Bailey‐Lovie logMAR letter charts that varied in contrast from 0.40 dB (C = 0.95) to 58.0 dB (C=0.001) were used to measure the middle and high spatial frequency range of the contrast sensitivity function (CSF) of 15 subjects with age‐related maculopathy (ARM) and 15 age‐matched normal subjects. The letter charts were shown to have good test‐retest reliability. Compared with measures made using CRT generated square wave gratings of variable contrast and spatial frequency they were also shown to provide a valid measure of CSF in the mid to high spatial frequency range. The 20.0 dB letter chart alone was shown to be a good screening device for macular disease. The letter charts do not provide a measure of the peak of the CSF and a supplementary test of contrast sensitivity is needed to quantify contrast sensitivity at a low spatial frequency. Three measures are proposed as necessary to document foveal visual capability of patients with macular disease: distance logMAR visual acuity to measure high spatial frequency resolution, visual acuity with letter charts of 20 dB contrast to assess mid spatial frequency resolution; and contrast sensitivity for the detection of an edge to estimate contrast sensitivity for larger objects.