CRITICAL FLICKER FREQUENCY IN ACUTE AND RECOVERED OPTIC NEURITIS

Multiple occasional changes in critical flicker frequency (CFF) were s tudied in patients who recovered from optic neuritis. Twenty-five pati ents (31 affected eyes) with onset visual acuity less than 0.5 and who showed recovered visual acuity exceeding 1.0 were included in this st udy. Recovery stages were determined individually as follows: T1, init ial onset stage; T2, intermediate stage; T3, recovered stage when visu al acuity was 1.0 or better; and T4, final follow-up stage. CFF was de termined using red, yellow and green illuminated targets in a compact CFF measuring device recently developed at our department. The rates o f abnormality were 100% at stage T1 for all colors, and gradually decr eased as the stage advanced from T2 to T4. However, the rates of abnor mality continued to be high at 67% in stage T3 for the red target and 37% in stage T4 for the red target. The rates of abnormal interocular difference in CFF in 15 unilateral optic neuritis patients were 100% f or all colors at stage T1 and decreased gradually with recovery. Sligh t but definite abnormality of CFF was also noted in the silent eyes of clinically unilateral optic neuritis patients. The rates of abnormal CFF more than 7% in all colors could be detected in T1, T3 and T4. The se results indicate that CFF abnormality can be detected even at the s tage of recovery in the pathologic eyes and the fellow eyes of optic n euritis patients. CFF was also shown to be a sensitive indicator for d etecting visual dysfunction in patients with optic neuritis.