Functional vision tests as clinical trial outcome measures in ophthalmology: a scoping review

To identify currently available functional vision tests and evaluate their use as clinical trial outcome measures in ophthalmology.

Scoping review using the PRISMA-ScR (Preferred Reporting Items for Systematic Reviews and Meta-analysis Extension for Scoping Reviews) guidelines.

A literature search was conducted in MEDLINE and Embase (via Ovid) for articles published between 1 January 2003 and 1 August 2024. Additional grey literature was sourced from institutional repositories, conference proceedings and a manual citation search. Article screening was conducted against a predefined inclusion criteria by two independent, masked reviewers, with a third reviewer acting as arbiter. The inclusion criteria were English language articles which feature a test assessing functional vision in patients with an ophthalmological disease. Details of source characteristics, test methodology and accessibility and evidence of test validation were collected.

Of 2665 articles returned by the search, 73 were included and 45 unique tests of functional vision were identified. Diseases affecting the peripheral retina were mainly affected, accounting for 77% (56 out of 73) of the diseases featured in all included studies. Overall, 82% (37 out of 45) functional vision tests reported evidence of statistical validation with varying robustness. Functional vision tests were mapped to domains of orientation and mobility, facial recognition, observer-rated task performance, visual search and driving. Obstacle courses assess vision-guided orientation and mobility, correlate highly with clinical measures of visual function in severe peripheral retinal disease and have been validated for use in clinical trials. Their requirement of physical space and time limits utility in multicentre trials; equivalent tests leveraging virtual reality and eye tracking technologies are in development. Early iterations of visual search tests to simulated realistic scenes have demonstrated discriminative ability, even in paediatric patients.

Functional vision tests can facilitate research into future novel ophthalmological treatments that prioritise patients in terms of how clinical benefit is defined. The principal barriers to the uptake of these tests are lack of accessibility, low quality validation and that many tests remain early in their development stage. This review captures the current landscape of functional vision tests and serves as a reference for investigators and regulatory bodies to evaluate the suitability of these tests for ophthalmic clinical trials.