Proposed New Vision Standards for the 1980's and Beyond: Contrast Sensitivity

Abstract : Research shows that present visual standard tests, generally based on the observer's ability to see small high contrast black and white symbols, are not adequate to evaluate an individual's target detection and recognition capability over ranges of target size and contrast used in real situations. New vision tests being developed use the observer's report of the visibility of sine-wave gratings (that look like fuzzy bars) to assess visual capability with much more sensitivity than that of standard tests. The new contrast sensitivity tests, assess vision using the same method used to assess hearing. Just as hearing tests use sound intensity and temporal frequency to measure audiometric sensitivity, contrast sensitivity tests use contrast and spatial frequency to measure visual sensitivity. The relationship between contrast sensitivity and eye charts is discussed using normal and abnormal vision. Although standard eye charts are useful to create an in-focus image in the back of the retina, contrast sensitivity techniques are needed to measure the next physiological state that determines the observer's response to that image. Data are presented that reveal individual differences in contrast sensitivity among normal observers that have definite implications for visual performance in operational environments. Since these differences in visual sensitivity can relate to detection and recognition ranges, these data can be transformed into time to perform certain tasks and lead naturally toward visual standards being based on task performances under operational conditions.