Scotopic Microperimetry: A Volumetric Analysis of Healthy Controls

Abstract

Purpose : Scotopic microperimetry involves fundus-controlled perimetry performed in dark conditions, enabling spatial assessment of scotopic macular sensitivity. Volumetric analyses have been shown to reflect central retinal sensitivity more accurately but are yet to be applied to scotopic microperimetry. We investigate normative volumetric sensitivity values and their repeatability in two-colour scotopic microperimetry in healthy participants.

Methods : Macular sensitivity in 23 healthy participants was assessed using S-MAIA Microperimeter (Centervue SpA, Padua, Italy) displaying a 37-point radial grid, following 20 minutes dark adaptation (light level <1 lux). Both eyes in each participant were assessed with cyan (505nm) stimuli followed by red (627nm) stimuli, with sensitivity measured in decibels. A sub-cohort underwent further testing in the right eye only within 5 weeks to assess repeatability. Comparative non-parametric statistics using SPSS (IBM Version 25.0.0.1) were applied. Hill of Vision volumetric analysis of results was performed using an open-source program.

Results : Mean retinal sensitivity and volumetric sensitivity in the right eye and left eye were obtained (Table 1, 45 eyes, mean age: 34.3 years range: 20-73). Fixation losses >20% as measured by blind spot losses were used to exclude exams from the final analysis. Median volumetric sensitivity in the right eye and the left eye with cyan and red stimuli were significantly correlated (Spearman’s Correlation, cyan ρ=0.871, p=0.001, red ρ=0.621, p=0.01, cyan-red ρ=0.468 p=0.068). There was no significant correlation between age and volumetric sensitivity (Spearman’s correlation, cyan ρ=-0.414 p=0.099, red ρ=-0.333 p=0.192). Coefficients of repeatability for volumes were calculated (cyan n=10 ±207.1dB-degrees², red n=12 ±367.5dB-degrees², cyan-red n=8 ±164.9dB-degrees²).

Conclusions : For the first time, we describe an application of volumetric analysis and correspond repeatability measures in scotopic microperimetry data. The strong inter eye symmetry suggests no significant learning or fatigue effects on test performance. In diseased patients, volumetric measures offer more detailed indication of function than simple mean sensitivity, so here we display a normative dataset from healthy participants.

This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.

 

Table 1: Mean sensitivity and volumetric sensitivity in a cohort of healthy participants