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.