V = standard view distance D ÷ distance at which each letter D' ................1
There is visual acuity under the eyes, on which the object cannot be determined
Factor factor mainly determines refractive error and contrast angle brightness or brightness and duration of contrast and exposure
The target resolution threshold is expressed as a small angle, which can reduce the distinction between important elements of the stimulus pattern such as a pair of dots.
Relaxation is specified in terms of its angular size