Home Visual Acuity Tests for Telehealth in the COVID-19 Era: Valid or not?

With increased use of telehealth technology, it is crucial to ensure that quality of care remains optimal. A key factor in evaluating and treating patients during eye care visits is the VA measurement. During a clinical encounter, this measurement is taken at specific distances using standardized charts, including Snellen, Early Treatment Diabetic Retinopathy Study(ETDRS), HOTV, and Tumbling E charts. Historically, VA testing has been done exclusively in a clinical setting under the guidance of a trained professional, but in recent years, various options have been created for testing outside of the clinic, including paper charts, web-based tests and smartphone applications.

A significant barrier to implementation of these new VA tests is translation to at-home use, as many of the studies were performed in the clinical or research setting and used trained staff to administer the tests. These study designs pose significant constraints on the ability to extrapolate the findings to the real-world conditions of self-administered VA testing at home. A few recent studies have validated paper chart acuity tests and a web-based test under home conditions.

Beyond the few self-administered studies discussed above, there are few data about the accuracy and usability of different types of self-administered VA tests validated under home conditions. The study by Kellyn N. Bellsmith aims to fill that knowledge gap because validation of at-home VA tests remains necessary to deliver reliable teleophthalmology care during the ongoing COVID-19 pandemic. This report compares 3 types of at-home VA measurement to standard in-office VA testing and seeks to validate the accuracy and usability of these tools.

Between July 2020 and April 2021, eligible participants with VA of 20/200 or better were recruited from 4 university-based ophthalmology clinics (comprehensive, cornea, glaucoma, and retina clinics). Participants were prospectively randomized to self-administer 2 of 3 at-home VA tests (printed chart, mobile phone app, and website) within 3 days before their standard-of-care clinic visit. Participants completed a survey assessing usability of the at-home tests. At the clinic visit, best-corrected Snellen distance acuity was measured as the reference standard.

Three types of at-home VA tests were compared in this university-based study completed during the COVID-19 pandemic. Because authors wanted to avoid accessibility bias, they chose 3 tests that were readily available to the public at no cost. The tests differed in access method (printed, mobile phone app, or website), and the mobile phone app and website tests were near acuity tests while the printed chart measured distance acuity. This diverse group of tests was purposefully selected to expand the types of VA tests validated for self administration under home conditions.

There were 4 key findings in this study.

First, all 3 at home self-administered VA tests were valid within 1 line of in-office Snellen acuity. These results were similar to other smartphone-based tests, including Peek Acuity, with a mean difference of −0.07 logMAR between the in-office ETDRS acuity and the Peek Acuity app administered in the clinic with staff guidance. The Home Acuity Test, an open-source VA screening test that was validated under home conditions, also performed similarly with a mean difference of −0.10 logMAR compared with the ETDRS logMAR chart in the clinic.

Second, the printed chart had the smallest mean difference and greatest correlation compared with the in-office acuity measurement, although there was no statistically significant difference among the 3 tests. This study is one of the first to test a mobile phone app and web-based test under home conditions.

Third, older participants in the study were more likely to be enrolled in the mail-only cohort compared with the randomized cohort, suggesting older participants may not have had adequate access to internet or iOS devices to qualify for randomization in this study. As many older patients may benefit from at-home acuity testing, access to technology for this group appeared to be a barrier for some patients.

The final key finding was that participants found all 3 tests easy to use and expressed some interest in future at home testing. Feedback from participants using all forms of at-home testing indicated that participants did not want their in-office acuity testing replaced by at-home acuity measurements because of concerns about accuracy.

Based on these data, it appeared that at-home VA tests may be best used to reassure patients and clinicians when there is no significant change in VA. However, given the lower PPV values, the at-home tests may not be as useful for identifying true change.

It appeared that home acuity tests were more likely to report slightly decreased VA compared with clinical acuities, possibly due to the testing modality itself, including contrast and brightness, and the means of administering the test, including lack of technician oversight and possible distractions at home. Overall, it seems most beneficial to have an at-home acuity test slightly underestimate rather than overestimate acuity for purposes of remotely detecting VA changes.

This study validated 3 publicly available, free, at-home VA tests that were self-administered under home conditions. Participants were of various ages from multiple clinics and represented urban and rural populations, which increases generalizability of the study findings. The COVID-19 pandemic has created an opportunity for expansion of teleophthalmology services due to the necessity of limiting in-person exposures. The lessons learned in this context may have important implications for rural eye care, as well as eye care in other outreach settings or underresourced areas. Visual acuity remains a key clinical data point for eye care professionals when making diagnostic and treatment decisions. Validated at-home tests provide an important first step in the expansion of teleophthalmology.

Source: Kellyn N. Bellsmith, MD; Michael J. Gale, MD; Sen Yang; JAMA Ophthalmol. doi:10.1001/jamaophthalmol.2022.0396