Tue 2 Feb 21
A low-tech sight test, which can be done from the comfort of your own home and without the need for any specialist equipment, has proved accurate at estimating a patient’s level of vision.
Since the start of the pandemic optometrists and ophthalmologists across the country have increased the use of phone and video consultations and at London’s Moorfields Eye Hospital alone, this has led to over 100,000 appointments taking place online or by phone.
With this in mind experts from Moorfields Eye Hospital and the universities of Essex, Cambridge and University College London, set out to devise a low-tech way to conduct eye tests remotely, which would provide consistent accurate testing without the need for specialist equipment.
Their Home Acuity Test (HAT) can be printed on A4 paper and posted to patients. In trials it has proved to be a good alternative to clinic-based tests.
Dr Matteo Lisi, from the Department of Psychology at Essex explained: “During the pandemic many opticians have had to change their way of working to keep patients safe and stop the spread of coronavirus, including asking their patients to do self-assessments, by for example reading television subtitles. We wanted to provide them with a more scientific alternative, which met industry standards and had been proven to work.”
150 participants took part in the trial – two-thirds with known visual impairments, and the remainder with no sight issues.
Patients were sent two HAT charts along with Blue-Tac to fix them to a wall and a 150cm length of string to measure chart viewing distance. They were then phoned by a clinician, and asked to cover each eye in turn and read the chart from the required distance, using glasses if necessary. The number of letters read correctly was recorded and the results compared with the last traditional eye test they had had at a clinic.
Michael Crossland, senior optometrist at Moorfields Eye Hospital, said: “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 at Moorfields and we are encouraged by our results.
“The test can be downloaded free of charge from homeacuitytest.org, doesn’t require any specialist equipment, and can be posted to people who are not able to access the internet at home.”
Home tests obviously differ from those offered in a clinic. At home it is not possible to measure contrast in the same way, the lighting at home is likely to be much lower and patients may not follow instructions as well. Despite these problems, researchers found similar results from both the HAT test and the previous clinic-based test.
“Measuring vision at home is unlikely to ever be as accurate as in-clinic assessment by a trained clinician, but we have shown the HAT can be used to measure vision by telephone for a wide range of ophthalmology outpatients with diverse conditions, including those who are severely visually impaired.
"By avoiding digital devices, it is likely to be accessible to more of the population, and less liable to unexpected variation in performance,” added Dr Lisi.
Patients will be tested again, as soon as clinics can fully open, to check whether the home test has picked up all visual changes. Patients who demonstrate changes to their vision will be given the appropriate treatment throughout.
The research team included Michael Crossland, Joanne Hancox and Peter Thomas from Moorfields Eye Hospital; Matteo Lisi from the University of Essex, Tessa Dekker from University College London and Thomas Wemyss from University of Cambridge.
The results from their study have been printed in JAMA Ophthamology.