Measurement of contrast sensitivity has been used in experimental and clinical research for several decades, in some places also in routine examinations of patients with different vision problems, especially diabetes, multiple sclerosis, glaucoma, macular degeneration, and brain damage related vision loss. The use of contrast sensitivity measurements is still limited, which may lead to misunderstanding of the quality of visual functioning. Visual recognition functions at full contrast are measured with optotype test to evaluate recognition of forms and shapes and with grating tests to evaluate resolving of lines. Contrast sensitivity is measured similarly using both optotype and grating tests.
In order to discuss contrast sensitivity we need first to define what we mean with contrast.