Tablet-based perimetry could help triage glaucoma patients
This study evaluated a free, tablet-based triage perimeter (Eyecatcher) as a means of quickly identifying patients with glaucoma who are at risk of developing vision loss.
Researchers tested Eyecatcher on 77 individuals who were waiting for a routine appointment at a UK glaucoma clinic. The cohort included new referrals and patients with an established diagnosis. Participants were asked to sit 55 cm in front of a tablet device and simply look at anything they see appear on the screen. A clip-on eye tracker determined whether the participant was looking at the targets; there was no response button or central fixation target. Stimuli were Goldman III targets. The computed summary measure of performance is potentially comparable to mean deviation on a Humphrey Field Analyzer (HFA). Patients also underwent monocular standard automated perimetry (SAP) using an HFA. Participants were asked to complete 2 identical questionnaires for Eyecatcher and conventional SAP.
Overall, there was good association between the 2 approaches. Eyecatcher was faster than SAP (median duration 2.5 vs. 3.5 minutes) but SAP tested more locations and measured threshold at each location. The median duration did not include additional overheads—such as time to position participant and explain the test—which can be extensive for SAP but minimal for Eyecatcher. The tablet-based method localized scotomas with reasonable spatial precision but sometimes underestimated or incorrectly localized visual field loss.
Eyecatcher did not diagnose participants with substantial field loss as normal, though some patients with healthy visual fields did score poorly. It led to good separation of eyes with advanced field loss and those within normal limits, and marked two-thirds of false-positive referrals as functionally normal. Although participants rated Eyecatcher as more enjoyable, less tiring, and easier to perform, it was less repeatable than conventional SAP.
Since this study was an initial feasibility assessment, additional studies are needed to formally evaluate diagnostic accuracy, assess economic utility, and test performance with various target intensities. Eyecatcher itself also presents several limitations. Seven individuals could not complete the test because the hardware could not reliably track their eyes. Since it requires an eye-movement response, Eyecatcher cannot test central vision. Finally, Eyecatcher has high specificity but limited sensitivity for false-positive referrals, though this was partly by design because it is worse to incorrectly flag an eye as healthy than it is to incorrectly flag a healthy eye as diseased.
Fast, easy, and portable visual field testing is a hot topic, and there is a demand for convenient screening methods for glaucomatous field loss. Tests that can be done in the waiting room or even from the comfort of home could be useful, especially in this COVID era. Eyecatcher was intended as a rapid triage measure for use in clinics, but its portability and ease of use could make it useful for at-home monitoring or glaucoma screenings in rural communities. It could also be used for visual field assessments in patients with limited physical or cognitive abilities.