Effect of polarized sunglasses on visual functions.

AIM: To evaluate the effects of polarized and non-polarized sunglasses on visual functions, including distance and near visual acuity, phoria, stereopsis and contrast sensitivity across five spatial frequencies (1.5, 3, 6, 12, 18 cycles/degree). METHODS: A before-after study was conducted on 45 emmetropic students from Shahid Beheshti University of Medical Sciences. Visual acuity, contrast sensitivity, stereopsis and phoria were measured under three conditions: without sunglasses, with non-polarized sunglasses and with polarized sunglasses. Tests were conducted under controlled glare conditions to simulate outdoor environments. RESULTS: A total of 45 participants were evaluated, comprising 17 males (37.8%) and 28 females (62.2%). The mean age was 21.67±2.31y (range 18-27y). The mean of distance and near visual acuity in all three conditions were equal to 0.00 logMAR. Contrast sensitivity generally decreased slightly with the use of non-polarized sunglasses compared to the no-sunglasses condition. The mean stereopsis with polarized sunglasses was 101.33±56.139 arc sec, which was worse than the no-sunglasses condition (94.33±46.632 arc sec) and better than the non-polarized sunglasses condition (105.67±58.965 arc sec), although these changes were not significant. In the phoria parameter, distance phoria appeared more affected than near phoria. CONCLUSION: Polarized and non-polarized sunglasses do not significantly affect visual acuity, stereopsis, or phoria under controlled glare conditions. Slight changes in contrast sensitivity are noted, but they are not statistically significant.