Test-Retest Variability of Fundus-Tracked Perimetry at the Peripapillary Region in Open Angle Glaucoma.

Purpose: To examine the association between the measured level and local gradient of visual sensitivity on the magnitude of test-retest variability of its measurements at the peripapillary region using fundus-tracked perimetry in eyes with glaucoma.

Methods: A total of 30 participants with open angle glaucoma underwent three examinations in one eye on fundus-tracked perimetry using a stimulus pattern that sampled the peripapillary region densely. Factors associated with the magnitude of test-retest variability at each location were examined.

Results: There was no significant change in average pointwise sensitivity (PWS) between tests 1 and 2 (P = 0.855), but a significant reduction between tests 2 and 3 (P < 0.001). Therefore, all subsequent analyses were performed only between tests 1 and 2. Multivariate analyses revealed that the magnitude of test-retest variability at a given location was significantly associated with its average sensitivity and gradient of sensitivity relative to the immediately adjacent locations (P ≤ 0.001), meaning that locations with low levels of sensitivity (4-18 dB) with low gradients of sensitivity (<2 dB/location) had a 90% test-retest limit of ±5.83 dB, compared to a limit of ±10.65 dB in areas of high gradients of sensitivity (>4 dB/location).

Conclusions: On a pointwise basis, the test-retest variability of visual sensitivity in glaucoma is not just related to its measured level, but also its local gradient when using fundus-tracked perimetry. Locations with low sensitivity do not necessarily demonstrate very high test-retest variability, depending on the local uniformity of visual field damage.