Acuity - 2
	u Measures of Acuity l 20/20:   can see at 20’ what a normal person can see at 20’. u This is normal, not perfect, vision.    20/200:   can see at 20’ what a normal person can see at 200’. l Visual angle of the critical feature in a test, e.g. the width of the bars in a grating. u A typical population average is 1 arcmin (1/60 degree). u Acuity and Retinal Location: l Best at fovea.  Falls off rapidly in periphery.  Is tied to density of cones.