The theory of critical flicker fusion frequency and its application in cataracts

Background:Due to media opacity,it is usually difficult to accurately evaluate the postoperative visual acuity in cataracts patients.As a small and portable tool,the critical flicker fusion frequency(CFF)device reflects the temporal resolution of visual function and has been widely used in clinical research.However,poor understanding of the technique and equipment limitations have restricted its clinical application in China.Main text:There was a decrease in the CFF value in various ophthalmic diseases,indicating that the CFF is sensitive to detect visual functional changes.A number of studies have shown that the CFF test can accurately distinguish patients with simple cataracts from those with cataracts combined with fundus disease,and,as a visual test,it can more accurately predict postoperative visual acuity without being affected by media opacity.This study comprehensive reviews the basic principles of CFF and its application in ophthalmology,especially in cataracts.Conclusions:As one of the tools for dynamic visual function detection,the CFF test could help doctors to assess the possible presence of fundus disease in cataracts patients,especially in eyes with dense cataracts,and more precisely provide a reasonable visual prognosis than other available visual tests.

The clinical application of critical flicker fusion frequency in demyelinating optic neuritis

Purpose:To investigate the application of critical flicker fusion frequency(CFF)in demyelinating optic neuritis(DON).Methods:A cross-sectional study.A total of 127 eyes in 69 DON patients and 63 eyes in 33 healthy control(HC)groups were included between January 2021 to September 2021 from Department of Ophthalmology,PLA General Hospital.Patients underwent best-corrected visual acuity(BCVA),visual field,optical coherence tomography(OCT),flash visual evoked potential(F-VEP),and CFF examinations.The affected eyes were divided into aquaporins 4(AQP4-),myelin oligodendrocyte glycoprotein(MOG-),and double negative DON according to serum antibody;mild,moderate,severe degree visual impairment according to BCVA
0.5,0.1-0.5,<0.1;and 4 groups:<1,1~<3,3~<6 and>6 months according to time interval from onset to CFF examination.One-way ANOVA was used to perform above subgroup analysis.The correlations between CFF and F-VEP peak time,peak value,BCVA and mean visual filed defect(MD)were analyzed in order via Pearson correlation analysis.Results:he trichromatic values of red,green,and yellow in DON affected eyes were 21.83±9.03,23.66±10.21,24.09±10.77 Hz,respectively,which was significantly reduced compared with the HC group(t=-14.82,-14.22,-14.00;P<0.001).The subgroup analysis showed no significant difference between different antibody subtypes(P=0.914<0.848<0.604),whereas,a significant decrease of CFF trichromatic value was found in severe visual acuity impairment group(P<0.001).There was a significant difference in CFF-trichromatic values at different time points(P<0.001),to be specific,CFF fluctuated under 20Hz within 3 months after onset and tended to be stable around 24-28Hz.Correlation analysis showed that the peak time of F-VEP(r=-0.486,-0.515,-0.526;P<0.001),BVCA(r=-0.640,-0.659,-0.642;P<0.001),were negatively correlated with CFF trichromatic values,MD and CFF were positively correlated(r=0.486,0.453,0.476;P=0.003,0.006,0.004).Conclusions:A significant decrease of CFF value was found in DON-affected eyes,and it has a good correlation with BCVA,MD and latency of F-VEP,and can better reflect the impairment of visual function.