Low luminance visual acuity as a clinical measure and clinical trial outcome measure: a scoping review

Abstract

Purpose The measurement of standard visual acuity (VA) is the most well‐known part of any ophthalmic examination to indicate visual function. Despite this, it is insensitive in detecting early disease changes. Therefore, other visual function tests have been developed including low luminance VA (LLVA) and low luminance deficit (LLD). This scoping literature review aims to summarise the current published applications of LLVA and LLD assessments to evaluate their utility as clinical markers and research outcome measures in a variety of ophthalmic conditions. Recent findings Sixty‐five peer‐reviewed publications were included. LLVA was pioneered for use in geographic atrophy, a subtype of age‐related macular degeneration, which remains the mainstay of its clinical application. However, other studies have reported additional useful applications in inherited retinal diseases including rare maculopathies and rod‐cone dystrophies. Although there are some variations in testing methodology, use of the standard Early Treatment Diabetic Retinopathy Study (ETDRS) chart with a 2.0 log unit neutral density filter is the most popular approach. The optimal testing luminance is still to be defined. Summary Overall, LLVA is an earlier clinical marker of change in central retinal function than standard VA. It has been shown to be a risk factor for disease progression and a better indicator of a patient’s level of everyday visual function. It is inexpensive and simple to implement using readily available standard ophthalmic equipment.

Phase 1B study of the safety and tolerability of the mineralocorticoid fludrocortisone acetate in patients with geographical atrophy

“…LLVA is a known predictor of visual loss in patients with GA, where it can detect a change in central function earlier than standard VA assessments 25–27. Our findings show that LLVA did not deteriorate over the study period may be considered promising, and worthy of a more detailed study to be conducted in a larger cohort.…”

Age‐related normal limits for spatial vision

“…54 Despite the obvious advantages of testing VA in the mesopic range and the availability of open source software to carry out VA and contrast sensitivity tests, 55,56 standard methods have not been developed and upper normal limits of spatial vision in the mesopic range have not been established. 7,57,58 This makes screening for abnormal responses and the comparison of results from different studies difficult to carry out. Binocular vision yields significant improvements in many aspects of vision, particularly in the mesopic range.…”

Prediction of visual function from automatically quantified optical coherence tomography biomarkers in patients with geographic atrophy using machine learning

“…To assess visual function in AMD, visual acuity (VA) measured using an eye chart under standardised lighting is an established key outcome measure as defined by the International Consortium for Health Outcomes Measurement 3 . Interestingly, in early stages of AMD, VA measured under low luminance conditions (low luminance visual acuity [LLVA]) can be reduced whilst standard VA remains unaffected 4 , 5 . Most patients initially present with non-central GA (affecting the parafoveal region of the macula) and gradually proceed to foveal involvement (central GA) 6 – 8 .…”