Exploring spatiotemporal summation in age-related macular disease

Abstract

Increasingly, microperimetry is used to measure visual function at pre-defined locations across the central visual field in age-related macular disease (AMD), in trials of novel therapeutics and clinical practice. It has the advantage of retinal tracking, permitting adjustment of stimulus position to compensate for fixation instability, known to increase in AMD. However, microperimetry suffers from significant limitations including poor sensitivity to early AMD and limited dynamic range. The overarching aim of this thesis was to determine if such limitations could be reduced by selecting more appropriate stimulus parameters and test background luminance. This was addressed through (1) investigation of spatial summation across the central visual field in healthy observers under mesopic conditions, (2) investigation of changes in spatial and temporal summation in AMD, (3) quantification of the relationship between visual function (measured with stimuli scaled to probe alterations in spatial summation) and retinal structure, and (4) assessment of the influence of stimulus parameters on intra-test fixation stability. We observed the upper limit of complete spatial summation (Ricco’s area, RA) in healthy observers to be invariant of visual field location in mesopic conditions. Under photopic conditions, RA varied significantly across the central visual field and was enlarged in participants with early, intermediate and atrophic AMD compared to controls. No changes in temporal summation were observed with visual field location or between AMD and control cohorts. Thresholds were significantly related to OCT measures of whole retinal thickness in AMD, this relationship being significantly improved using RA-sized stimuli compared to Goldmann III. Fixation stability was reduced by longer durations and when stimuli were visible, but may be improved using stimuli

Date of Award	May 2021
Original language	English
Sponsors	Macular Society
Supervisor	Padraig Mulholland (Supervisor), Roger Anderson (Supervisor), Tony Redmond (Supervisor) & David F. Garway-Heath (Supervisor)