The influence of the stimulus width on the contrast sensitivity function in amblyopia.

The contrast sensitivity function of both eyes of subjects with functional amblyopia has been measured. A clinically significant difference was found between the amblyopic and the normal eye. It appears that the functionally amblyopic eye takes more information from the peripheral parts of the stimulus than does the normal eye. The sensitivity of the normal eye increases linearly with increasing width of the stimulus to show a knee at a certain number of grating lines, whereafter the sensitivity remains constant. The sensitivity of the amblyopic eye initially rises much faster than that of the normal eye with increasing stimulus width. In the amblyopic eye, there is no definite linear relationship between width of stimulus and the contrast sensitivity and no definite knee in the curve at which maximum sensitivity is reached.