Microperimetry as an Outcome Measure in Choroideremia Trials: Reproducibility and Beyond.

PURPOSE: To determine test-retest repeatability of microperimetry testing (MP) in choroideremia (CHM) subjects using standard and personalized stimulus grids.
METHODS: Fifteen CHM subjects (28 eyes) underwent consecutive repeat examinations with the Macular Integrity Assessment (MAIA) microperimeter using a standard (10°) and a customized macular grid adapted to individual macular pathology. Repeatability of standard-grid mean (MS) and point-wise (PWS) sensitivity was determined and compared with age-matched controls (seven eyes), with PWS separately analyzed for loci within and outside the border of degeneration. Interpolated volumetric indices were used to estimate repeatability of customized grids and compare their performance to standard grids.
RESULTS: Test-retest measures of standard-grid MS yielded higher coefficients of variation (CV) in CHM subjects compared with controls (0.09 vs. 0.02). Volumetric indices from customized grids improved repeatability by driving CV values to 0.05 and close to 0.02 for region-of-interest (ROI) analysis. Variability of PWS was significantly higher in CHM, especially at the border of degeneration (10.68 vs. 4.74 dB at the central retina, P < 0.001).
CONCLUSIONS: Microperimetry testing in CHM shows high test-retest variation at the border of degeneration, which influences repeatability of MS measures. Volumetric measures from customized grids can improve reliability of both global and regional sensitivity assessment. Nevertheless, inherent test-retest variation of individual points needs to be taken into account when assessing potential functional decline and/or disease progression.