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Published on: February 15, 2022
Improvements in Test-Retest Variability of Static Automated Perimetry by Censoring Results With Low Sensitivity in
Ava K Bittner1,2,3, Anushka Mistry2, Leon Nehmad2
1Department of Ophthalmology, Stein Eye Institute, University of California, Los Angeles, Los Angeles, CA, USA.
Purpose:
We evaluated whether omitting (censoring) points in more severely damaged visual field areas can reduce test-retest variability of static automated perimetry (SAP) in retinitis pigmentosa (RP), as variability creates a significant challenge when monitoring for changes.
Methods:
Cohort 1 included 27 eyes in 16 RP subjects with visual acuity (VA) ranging from 20/20 to 20/70 who completed Humphrey 10-2 size III SAP, once per visit at three visits. Cohort 2 included 15 eyes in nine RP subjects with VA ≤ 20/60 who completed Humphrey 30-2 size V SAP, twice per visit at three visits. Variability was assessed using 95% coefficient of repeatability (CR) calculations for uncensored (all threshold values and data points included) and censored data.
Results:
In cohort 1, the uncensored between-visit 95% CR was 11.6 decibels (dB); censoring locations with threshold values of <8 to 20 dB resulted in 31% to 53% reductions in the 95% CR. For cohort 2, uncensored 95% CRs were 8.7 and 8.0 dB for within- and between-visit variability, respectively; censoring <8 to 17 dB resulted in 15% to 41% and 15% to 43% reductions in within-visit and between-visit 95% CRs, respectively. For both cohorts, censoring at higher values yielded slightly less variability, at the expense of discarding data from a greater number of eyes and test locations.
Conclusions:
For 20/20 to 20/70 VA tested with size III stimuli, censoring lower sensitivity values results in substantially lower test-retest variability, which may help detect true changes for locations without severe baseline loss.
Translational Relevance:
A rule of thumb for clinical practices using SAP to monitor RP is that longitudinal losses of >9 dB for individual test locations with initial values ≥ 9 dB are likely to be real and meaningful, as they exceed typical variability.
