Critical examination of existing monocular visual acuity data has allowed a n estimate of the informational capacity of a human eye to be made in this paper. The problem, analogous to that of the ear ( I ) , is simpler in that visual acuity is ordinarily measured in a way which allows a calculation of total numbers of yes-no decisions, i.e., the standard informational w i t s of "bits" (binary digits) to be made directly. The maximum acuity of the eye, measured as the inverse of the minimum angular distance necessary to resolve two objects under conditions of good illumination and central fixation is 60/degree (1' of arc is the acuity angle) fo r a person with '(normal," or Snellen 20/20, vision. Consensus of data (2-5) indicates a variable, but higher, acuity figure fo r many eyes a t high illuminations. We have somewhat arbitrarily taken 100/degree as the maximum acuity. I f the visual pattern be regarded as a fine mosaic of "acuity squares," which are either black or white, of an area corresponding to the square of the acuity angle, lasting for a time of the order of the fusion period, the informational capacity can be calculated. The tacit assumption is that the acuity square can be recognized as either present or absent, in a complex retinal pattern, thus furnishing one yes-no decision, or bit of information. With the Landolt ring method of
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