Printable Chart Suitable for Stay-at-Home Visual Evaluation

By David Douglas

January 14, 2021

NEW YORK (Reuters Health) - A chart that can be downloaded or printed and mailed to patients appears effective in helping determine visual acuity via telephone assessments, according to researchers in the U.K.

"We are excited to be developing a simple test that clinicians can use to estimate the level of vision in patients who can't attend in-person appointments, which has the potential to be a great addition to the telephone and online appointments we provide and we are encouraged by our results," Dr. Michael D. Crossland of Moorfields Eye Hospital, in London, told Reuters Health by email.

In a paper in JAMA Ophthalmology, Dr. Crossland and colleagues note that because of the COVID-19 outbreak, more than 100,000 ophthalmology outpatient appointments were canceled at Moorfields over a three-month period.

Although video and telephone-based consultations have been used successfully, they add, measuring visual acuity (VA) remotely remains a challenge. Laptops require calibration and testing using smartphones has shown poor agreement with results of conventional vision tests. In addition, older and poorer patients have limited access to such devices.

In response, the team developed the Home Acuity Test (HAT) which contains 18 randomly selected Sloan letters displayed on five lines. This A4-sized document can be printed and mailed to patients or downloaded and printed at home. A silhouette of a credit card is included with the latter to ensure that the printed image size is correct.

To determine the HAT's utility, the researchers enrolled 100 ophthalmology patients with a wide range of diseases who self-described their vision as stable and 50 control participants all of whom had good corrected VA. Test repeatability was high, with test-retest differences ranging from -2 to 1 letters in control participants.

Patients were sent two HAT charts (with different letters on each) which they affixed to a wall. As part of their telephone assessment by a clinician, participants were asked to cover each eye in turn and to read the HAT from a distance of 150cm.

Analysis of corrected VA showed good agreement between the HAT and the last in-clinic VA measurement. "The mean difference in acuity was just more than 1 line of VA, and there was good crosstest agreement in categorical classification of visual impairment," the team writes.

The researchers note that since the study was conducted the HAT has been sent to more than 2,000 people receiving telephone assessments of low vision. Examination of a sample showed that 71% were able to complete the test and that the most common reason for noncompletion was failure for it to arrive in the mail.

"Measuring vision at home," they conclude, "is unlikely to ever be as accurate as in-clinic assessment by a trained clinician, but these findings show that the HAT can be used to measure vision by telephone for a wide range of ophthalmology outpatients with diverse conditions."

"The test," added Dr. Moorland, "can be downloaded free of charge from, doesn't require any specialist equipment, and can be posted to people who are not able to access the Internet at home."

Commenting on the findings by email, Dr. Graham E. Quinn, an emeritus professor of Ophthalmology at the University of Pennsylvania, in Philadelphia, told Reuters Health that the researchers "provide practical insight into the use of visual-acuity assessment of adults in a setting remote from the clinician's office."

"Though there are methodological issues including not testing each procedure at the same session, a remote unmonitored setting, and relying on the person being tested following procedures, the investigators have started an important conversation that may lead to more convenient and accessible assessment of visual function in adult patients," he added.

SOURCE: JAMA Ophthalmology, online January 7, 2021.