An electronic visual acuity chart may be a more accurate measure of how well a person sees than traditional ETDRS logMAR charts, particularly if the patient’s visual field loss has encroached on their central vision, a study in the British Journal of Ophthalmology suggests.
While the FDA favors visual acuity measurements with ETDRS charts, a team of researchers from the UK point out that the loss of visual fields can interfere with visual tracking, which can skew the results. Electronic visual acuity presents the letters in the center of a screen, thereby removing the tracking element of the task and providing a more precise measurement.
The study included 65 patients with rod-cone dystrophies and 41 healthy volunteers who had their visual acuity tested using ETDRS charts and electronic visual acuity automated single letter and single line charts. The researchers also tested the patients’ visual fields with microperimetry.
Both participant groups read two to three letters more, on average, when using the electronic charts compared with ETDRS. The researchers reported the limits of agreement were wider in eyes with foveal defects compared with normal eyes. In the presence of foveal defects, electronic charts reduced the range, the study noted.
Electronic presentation with a single line of letters was the favored style reported by patients and should be considered in future interventional clinical trials, the researchers said.
|Jolly JK, Juenemann K, Boagey H, et al. Validation of electronic visual acuity (EVA) measurement against standardized ETDRS charts in patients with visual field loss from inherited retinal degenerations. Br J Ophthalmol. October 4, 2019. [Epub ahead of print].