Abastract: The impact of glare is evaluated in a group of cataract patients and compared with a control group consisted of normal subjects. Contrast sensitivity functions (CSFs) with and without glare were measured. A Hartmann-Shack sensor was used to quantify the amount of cataract in each eye. The glare source had a negative impact on the CSF in subjects with cataracts, but there was not a significant impact in the control group. Differential CSFs may provide an additional approach to quantify the degree of cataracts.