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