Assessing adaptive optics corrected visual acuity in individuals with fragmented foveal avascular zones

Abstract

Purpose : It has been suggested that individuals with a fragmented foveal avascular zone (FAZ) have altered foveal photoreceptor distributions which would impact visual function.¹ Here we sought to compare adaptive optics (AO) corrected visual acuity in individuals with fragmented FAZs to those with normal FAZ morphology.

Methods : We recruited five individuals with fragmented FAZs (2M, 3F; Age range: 12 to 45 years, Avg = 27 years) and 16 individuals with normal FAZ morphology (6M, 10F; Age range: 11 to 67 years, Avg = 28 years). Stimuli (black Snellen E’s of varying sizes and orientations) were presented using a custom-built AOSLO (mean illumination wavelength 790nm, mean wavefront sensing wavelength 850nm). Individuals were asked to identify the orientation of each E in a four alternative forced-choice task. The orientation of each E was random, and the gap size of the E was driven by the individual’s responses by using two interleaved QUEST procedures. Prior to initiating each measurement block, the AO operator specified the number of E’s to be presented (typically 30-40 E’s per block). After 7-30 (Average = 13) blocks were performed, a psychometric function was fit to the data (using the Palamedes toolbox in MATLAB). The acuity threshold was defined as the log minimum angle of resolution (logMAR) in arc minutes from the psychometric fit function which corresponded to where individuals responded with the correct orientation for 62.5% of the E’s presented. Statistical analyses were performed using GraphPad Prism 9.

Results : The mean logMAR acuity for individuals with fragmented FAZs was -0.21 (0.62 MAR, 20/12.5 Snellen) with a standard deviation of 0.063 (range: -0.29 to -0.13). The mean logMAR acuity for individuals with a normal FAZ was -0.23 (0.59 MAR, 20/12 Snellen) with a standard deviation of 0.054 (range: -0.34 to -0.13). No significant difference in AO-corrected acuity estimates (defined as the psychometric fit threshold) was found between control eyes and eyes with a fragmented FAZ. (unpaired t-test; p = 0.33)

Conclusions : AO-corrected acuity measured at the fovea does not appear to differ between individuals with and without fragmented FAZs. Our findings are inconsistent with individuals with fragmented FAZs having altered photoreceptor distributions.

¹PMID: 31274711

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