The contrast sensitivity function in low vision.

The contrast sensitivity of 51 low vision patients (95 eyes) showed a substantial decrease in all spatial frequencies. The peak contrast sensitivity was shifted to 1 C/D from the normal 3-4 C/D. The high-frequency cut off is correlated to the visual acuity positively. Of the 33 patients, the preferred eye was the eye with better peak sensitivity in 28 patients (84%), while the preferred eye was the eye with better visual acuity in 22 patients (66%). It seems that the peak sensitivity is more important than visual acuity in determining eye preference. It provides a useful information for the clinician to determine which eye to train with low vision aids. Forty patients among 46 patients (87%) with RFN (Recognized Frequency Number) > or = 3 are able to read No.5 reading card, while 5 patients among 5 patients with RFN < 3 are not able to read No.5 reading card. The contributions of CSF to the low vision are evaluated.