Test–Retest Variability of Microperimetry in Geographic Atrophy

Abstract

Purpose : Microperimetry (MP) allows for measurement of retinal sensitivity at precise locations and is now commonly employed as a clinical trials endpoint. Test–retest reliability is important when evaluating treatment effects in patients with geographic atrophy (GA). This study aims to determine the test–retest variability of MP in patients with GA using the MAIA MP device.

Methods : In this prospective study, we enrolled 3 patients with a confirmed diagnosis of GA involving the fovea, best corrected visual acuity (BCVA) at or less than 20/80 and no previous MP testing. Participants performed three MP assessments of a selected eye over two visits (test 1 and 2 on visit one and test 3 on visit two; or test 1 on visit one and test 2 and 3 on visit two). MP testing was performed utilizing a wide 30° grid, consisting of 93 stimuli (Goldmann III) using a 4-2 representation strategy, encompassing the entire area of GA and beyond. Mean retinal sensitivity was expressed as an average threshold value (dB) for the entire field tested. Fixation stability was assessed by evaluating the area of an elliptical representation encompassing 95% of the fixation points (CFP) dataset generated by the MAIA MP, known as the bivariate contour ellipse area (BCEA).

Results : A total of 9 MP assessments were performed. BCVA in these patients ranged from 20/100 to 20/250. The mean time to complete one MP assessment was 14 minutes 13 seconds and mean BCEA@95% was 35.7° ± 15.3°. Fixation stability gradually worsened as the MP assessment progressed. The average retinal threshold was 15.6 ± 6.8 dB. An increase in average threshold values was noted between the first and second tests, and between the second and third tests. The preferred retinal locus was maintained in the same quadrant on successive tests.

Conclusions : Microperimetry using a wide grid can be reliably performed in a reasonable amount of time in patients with moderate and severe vision loss secondary to GA. There is a learning effect with increased average threshold values noted between sequential assessments. This effect was more pronounced between test 1 and 2 compared to test 2 and 3. Test–retest variability can therefore be minimized by discarding the first examination to avoid the influence of a learning effect.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.