Point-wise variability of threshold sensitivity of 24-2 and 10-2 visual fields

To evaluate point-wise variability of threshold sensitivity at different test locations on 24-2 and 10-2 visual field (VF).

Electronic medical records of patients seen at a tertiary eye care center were screened to include those with at least 3 reliable VF with glaucomatous defects involving fixation on 24-2 and confirmed on 10-2 test strategy. Ninety eyes of 90 patients were categorized into 3 severity groups based on mean deviation (MD on 24-2) test strategy; MD<-6 dB and >-12 dB, <-12 dB and >-20 dB and <-20 dB and >-30 dB. Variability of threshold sensitivity at all topographical test locations in central (ring 1), mid-peripheral (ring 2), peripheral rings on 24-2 VF test strategy (ring 3), and central (ring 4) and paracentral (ring 5) on 10-2 VF test along with variability of visual field index and central field index were calculated by multilevel mixed effects model.

Central ring1 on 24-2 and ring 4 on 10-2 showed higher variability (>10 dB) than peripheral ring 2, 3, and 5. Seventy-three eyes were adjudged as stable and 17 as progressing in this cohort. The average ring and point-wise variability was higher in stable eyes (2-6 dB) across all glaucoma severities. Across severity, variability was seen to decrease with increasing severity with minimal variability in point-wise threshold sensitivity beyond MD <-20 dB.

Central test points/ring on 24-2 and 10-2 with greater threshold variability suggests that status of the eye, severity and topographical location of test points should be incorporated into conventional progression algorithms to predict true glaucoma progression.