Abstract

Objective: Critical Flicker Fusion (CFF) function has been used to assess visual function in patients with impaired vision. The purpose of this study is to seek further evidence to support the role of the CFF in the assessment of optic nerve function by comparing CFF to implicit time of the P100 of Pattern Reversal Visual Evoked Potential (PRVEP) in normal subjects and patients who recovered from acute optic neuritis. Methods: 4 healthy adult subjects and 11 patients (14 affected eyes) who recovered from acute optic neuritis underwent PRVEP and CFF, as well as Snellen visual acuity and Ishihara color testing. For normal subjects, neutral density filters (NDF) of 0.6 to 3.0 log unit were used to control stimulus luminance to obtain response vs. stimulus intensity curve for each measurement. The CFF and PRVEP P100 latency were compared between the normal subjects and patients. Results: In normal subjects, CFF decreased 7.8 Hz (95% CI [7.4, 8.3], p < 0.001) and P100 latency increased 17.9 ms (95% CI [9.7, 26.0], p < 0.001) per log unit increase in NDF. Increasing NDF was also associated with decreasing logMAR acuity and decreasing P100 amplitude (both p < 0.001). In patients recovering from unilateral acute optic neuritis, CFF was significantly lower in affected than unaffected eyes. For all patients, affected eyes had significantly lower CFF than healthy eyes in normal subjects. PRVEP P100 latency did not differ significantly in the affected eyes of patients from the unaffected eyes of patients and normal subjects. Conclusion: Both CFF and PRVEP P100 latency are linearly correlated with log luminance. CFF is significantly decreased in the affected eyes of patients who recovered from acute optic neuritis. CFF may complement the currently used office tests to facilitate the assessment of optic nerve dysfunction.

Authors and Affiliations