Researchers have created a method of conducting sight tests at home without the need for specialist equipment in response to the pandemic.

The Home Acuity Test (Hat), which was printed on A4 paper and posted to patients, has proved to be ‘a good alternative to clinic-based tests,’ according to its developers.

Researchers explained that since the start of the pandemic, phone and video consultations have increased with over 100,000 conducted by Moorfields Eye Hospital.

A team from Moorfields, University of Essex, University of Cambridge and University College London devised the low-tech, remote sight test to estimate a patient’s level of vision.

Dr Matteo Lisi, from the University of Essex’s department of psychology, said: ‘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, for example by reading television subtitles.’

He added that it was designed as a more scientific alternative in order to provide consistent, accurate testing that did not require specialist equipment and met industry standards.

A trial involved 150 participants, with two-thirds known to have visual impairments and the remainder having no sight issues.

Patients were sent two Hat charts along with Blue-Tac to fix them to a wall, with a 150cm length of string to measure viewing distance.

A clinician then phoned the patient and asked them to cover each eye in turn and read the chart from the required distance, using spectacles if necessary.

The number of letters read correctly was recorded and the results compared with the last traditional sight test they had at a clinic or optical practice.

Researchers found that results were similar, despite not being able to measure contrast in the same way, different lighting conditions and patients’ ability to follow instructions.

Dr Lisi added: ‘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.’

Once clinics and practices reopen, patients would be tested again to check whether Hat has picked up all visual changes, with patients given appropriate treatment if necessary.

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.’

Results have been published in JAMA Ophthalmology and the Hat could be downloaded for free via its website, homeacuitytest.org.