Acuity - 2
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 rapily in periphery. Is tied to density of cones.