A Critical Flicker Fusion (CFF) test of potential vision [Post print]
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Purpose: To continue developing a potential vision test based on the critical flicker fusion (CFF) phenomenon by using a brighter stimulus and optimizing its size. Setting: The Flinders Eye Centre of the Flinders Medical Centre, Flinders University, South Australia. Methods: A prospective, non-randomized study with 225 participants (134 females, 59.8%; mean age 71.4!13.2 yrs) assigned to four groups: normal (n=41), media opacity only (n=61), retinal/neural disease only (n=61), and cataract plus retinal/neural disease (n=61). Participants were recruited into these groups if aged over 20 years, but were excluded if they had any neurological disorder or medication known to affect CFF. CFF thresholds were measured for three stimulus sizes (0.5°, 1.0°, 1.5°). Discrimination between groups was tested with ANOVA and Receiver Operating Characteristic (ROC) analysis. The relationship between visual acuity (VA) and CFF in eyes without media opacity was determined with linear regression and used to predict visual outcome of 23 eyes undergoing cataract surgery. Results: CFF thresholds were reduced in retinal/neural disease but resistant to image degradation from media opacity. The 1.5° stimulus had 88% sensitivity and 90% specificity for discriminating groups. Post-cataract surgery VA was accurately predicted within ±1 line in 43%, ±2 lines in 83% and ±3 lines in 100% of eyes All eyes with poor VA (>0.50 logMAR) or dense cataract (>4.0 LOCSIII) were predicted within ±2 lines. Conclusion: CFF effectively discriminates between subjects with and without retinal/neural disease and accurately predicts visual outcome after cataract surgery. The use of a brighter stimulus enhanced performance in dense media opacity.