Development of a critical flicker/fusion frequency test for potential vision testing in media opacities.

PURPOSE To determine whether critical flicker/fusion (CFF) thresholds fulfill the criteria for a potential vision test (PVT) by being unaffected by media opacity yet affected by retinal disease. METHODS CFF thresholds for three different stimulus sizes (0.5, 1.0, and 1.5 degrees ) were measured in 72 patients (mean age, 78.43 +/- 7.07 years) comprising 31 subjects with media opacity, 21 with macular disease, and 20 with pseudophakia. RESULTS There were no statistically significant differences between CFF values from the media opacity and the pseudophakia groups for any target size (p > 0.10). However, CFF values were significantly lower in patients with macular disease for all the target sizes (p < 0.05). Analysis of a subset of six subjects with media opacity and seven subjects with macular disease and visual acuity of 20/200 or worse showed the media opacity group still had similar CFF values as the pseudophakia group and had significantly higher CFF than the macular disease group. CONCLUSIONS CFF testing is shown to fulfill the requirements for a PVT and may prove to be particularly useful for patients with dense media opacity.