[Contrast sensitivity and visual acuity in animals].

BACKGROUND: Fundamental spatial vision capabilities of visual systems can be characterized by their contrast sensitivity and visual acuity.
OBJECTIVE: Comparison of contrast sensitivity and visual acuity in humans and other animals.
MATERIAL AND METHODS: An analysis of known contrast sensitivity functions and maximum visual acuity across selected taxa was carried out, with consideration of measurement principles, viewing conditions and allometry.
RESULTS: Comparing across all analyzed species, contrast sensitivity functions have inverted U‑shape characteristics, with key differences in both position and absolute sensitivity within the spectrum of spatial frequencies. Humans, for example, have a maximum sensitivity at 5 cycles/degree and mice at approximately 0.1 cycles/degree. Body and eye size generally correlate well with maximum visual acuity. Across eye types, lens eyes have the highest optical and visual resolution, all other things being equal. Diurnal species typically outperform crepuscular or nocturnal species. Humans generally excel at both maximum contrast sensitivity as well as visual acuity.
CONCLUSION: Despite great differences in optical, anatomical and neurophysiological structures between humans and animals, spatial vision capabilities are generally comparable across taxa. This favors the hypothesis that spatial vision in animals develops primarily towards meeting similar evolutionary needs within the limits of biophysical and optical laws.