Visual Function Assessment in Geographic Atrophy: A Review

Geographic atrophy (GA) causes significant vision impairment and reduction in vision-related quality of life. Fundus autofluorescence (FAF) is the gold standard of structural assessment of GA but is a surrogate marker for vision loss, which can be assessed by tests of visual function and functional vision. Best corrected visual acuity (BCVA), the most commonly used visual function test in ophthalmology, is a poor metric for assessing GA progression. This is because GA usually only affects the fovea in its late stage, grows slowly, and spared areas of retina may not 'fit' larger reading chart letters, confounding measurements. For this reason, tests of visual function have been developed, including low luminance visual acuity (LLVA), reading speed, contrast sensitivity, microperimetry, flicker perimetry, and dark adaptation. Functional vision measures are approximated through patient-reported outcomes using various questionnaires. This review explores the strength of association between FAF and tests of visual function in patients with GA. A range of targeted, prespecified endpoints of visual function testing should be included in future clinical trials for treatments of GA, focusing on GA lesion phenotypes that are known to progress rapidly in order to maximise the likelihood of identifying positive results. This is critical in jurisdictions where proof of functional benefit is required for regulatory approval of treatments for GA.