Contrast sensitivity in macular disease using a small-field and a large-field TV-system

The spatial contrast threshold for a sinusoidal grating of varying contrast and frequency generated with a small-field or a large-field TV-display was examined in normal subjects and in patients with macular disorders. Impairment of contrast sensitivity (reciprocal of contrast) was observed in the different maculopathies investigated. Attenuation of the high- and middle-frequency ranges was an early finding in macular disease, whereas changes including the low-frequency range was observed in more advanced maculopathies. Comparison of results obtained using the small (1.4 degree) or large-field (6 degree--24 degree) TV-system demonstrated a field-dependence of the contrast sensitivity attenuation in localized macular disorders. In more wide-spread lesions in the posterior pole, a contrast attenuation over the whole frequency range was found also with the largest (24 degree) stimulation field used. The study of the contrast sensitivity function supplements the traditional acuity measurements in quantifying the visual loss for objects larger than the resolution limit. I conclude that contrast threshold measurements are not only useful for describing visual loss, but also for tracking progression or recovery. The findings provide some additional insight into the visual difficulties of daily life of patients with a macular disorder. However, the definite role of contrast sensitivity measurements for diagnosing different visual disorders is still lacking.