Improvements in test-retest variability of visual field testing by censoring results with low sensitivity in retinitis pigmentosa patients

Improvements in test-retest variability of visual field testing by censoring results with low sensitivity in retinitis pigmentosa patients

Purpose: Variability of visual field data in ocular disease patients is a significant challenge when monitoring for vision changes. Omitting points in severely damaged areas in glaucoma patients reduced test-retest variability. We tested whether this approach would yield similar findings in retinitis pigmentosa (RP) patients. Methods: 40 eyes of 20 RP patients with vision worse than 20/70 completed Humphrey visual fields, twice per visit, on 3 separate visits (6 fields per eye), with threshold values determined for 76 test points. 95% coefficients of repeatability (CR) were calculated for each eye for all threshold values (uncensored), and for points that only included thresholds above values of 10-20 dB (censored). Results: Only 33 eyes in 17 RP patients had test locations with sensitivities ≥0 dB.Uncensored results had a 95% CR of 8.66 dB across 16 test points on average, while censoring points at the lowest level of <10 dB and highest level of><20 dB resulted in>95% CRs of 7.26 dB and 4.91 dB (16% and 43% reduction) for an average of 8 and 5 test locations for 22 and 7 eyes in 12 and 5 patients, respectively. Censoring at a mid-level of <15 dB resulted in a>95% CR of 6.19 dB (29% reduction) for 18 eyes and 10 patients, as a trade-off for loss of included eyes and reduction in variability.Conclusions: Censoring threshold values of lower sensitivity results in significant reduction in test- retest variability, but has the risk of losing data for eyes with severe visual loss.