Contrast sensitivity (the ability to distinguish between an object and it's background) was evaluated in a subgroup of subjects, and was tested monocularly (each eye) in photopic (well-lit) conditions, with a glare source, using sine waving gratings in a computerized testing system. The photopic spatial frequencies tested were 3, 6, 12, 18 cycles per degree (cpd). When a subject was unable to see the highest contrast grating, the highest contrast score was assigned. Raw scores (0 to 9) from contrast sensitivity testing were transformed to log units. Better results are reflected by a higher numeric value.