The use of critical flicker frequency (CFF) as a potential vision test prior to cataract surgery: a pilot study

Background: To determine whether a patient would benefit from cataract surgery, a pre-operative evaluation of retinal visual function is required. Age-related macular disease has been reported as the most important factor leading to poor outcome after cataract surgery. The critical flicker frequency (CFF) is a psychophysical test that measures temporal resolution properties in the visual system. Purpose: (1) To evaluate if CFF can be used as a tool to predict visual outcome after cataract surgery. (2) To assess if lens opacities and/or retinal damage affects CFF values. (3) To assess the optimal configuration for the CFF target in relation to stimulus size. Methods: Thirty-two patients have been included in the pilot study. Subjects were divided into the following categories: cataract, central retinal disease, pseudophakes and cataract after pupil dilatation. CFF threshold measurements were obtained after optimal refraction and visual acuity measurement using a Bailey–Lovie logMAR chart. A staircase method was used to find the CFF threshold. For each subject, three different stimulus sizes were analysed. Results: Critical flicker frequency measurements were unaffected by the presence of cataract (p > 0.05). Pupil dilatation gave slight higher results in patients with cataracts, although this difference was not statistically significant (anovaF = 3.6, p = 0.07). A significant difference for the three targets sizes was found (anovaF = 41.94, p 0.05, n = 5). Conclusions: Critical flicker frequency appears to be independent of the image degrading effects of cataract. Comparison of the means for the different conditions studied show a slight decrease in CFF measurement for retinal disease in comparison to the cataract group. However, more subjects are needed to determine the usefulness of CFF as a potential vision test.