Clinical psychophysics.

New developments in clinical psychophysics allow a non-invasive assessment of visual function which may otherwise not be possible. Measurements of spatial and temporal contrast sensitivity functions, perimetric rod and cone sensitivity, colour vision testing, and newer tests such as hyperacuity thresholds may provide information about the mechanism of an abnormality, allow earlier detection of damage, determination of retinal function in the presence of ocular media disturbances, and allow more sensitive detection of the effects of treatment on visual function. Some methods are more effective in screening or monitoring patients over time while others can be used as research tools to investigate the underlying causes of visual dysfunction. Emerging technologies such as those based on video displays and computer generated graphics and advances in methodology provide potential for new applications. The selection of which aspect of visual function to test depends on the condition (e.g., retinal degeneration or glaucoma), the goals of the investigation, and the facilities available. These non-invasive methods can provide accurate information about retinal function and further improve our ability to quantify and document this most important aspect of the eye--its role in visual function.