Repeated measures observational study of tablet-based children's visual acuity tests.

The most common disease seen in paediatric eye clinics is lazy eye (amblyopia), which affects 5% of the population. Amblyopia is treated using eye patching or eye drop therapy over the course of 6 months to two years. Up to half of all children undergoing therapy for amblyopia do not achieve a successful outcome. The outcome measure (visual acuity) is how small a letter the patient can see on a Snellen-like chart. Visual acuity is measured six-weekly for amblyopia patients in the outpatient clinic and is used to decide when to start therapy and how much therapy to use.

Recent developments by visual acuity test manufacturers of iPAD-based tests have simplified the testing protocol so that it may be performed by untrained staff. It is currently not understood to what level of accuracy a lay-person can perform the test. The present study was conceived to answer questions brought to us by patients and their parents, whom reported in our PPI activities that they feel they could use the iPAD themselves to test visual acuity.

This study is designed to quantify the correlation between iPAD-based visual acuity measurements taken by lay persons and the gold-standard, clinic-based measurements taken by qualified orthoptists using standard of care equipment and protocols. Collaboration between the PPI group and researchers expect that the correlation will likely be high and the teams anticipate possible advantages to lay-persons testing the visual acuity including, fewer visits to hospital and better adherence to amblyopia therapy.

Home visual acuity test has potential to reduce the number of outpatient clinic assessments or allow assessment of patients that could not be assessed during the UK coronavirus epidemic. However, the awarding body, BIOS, have requested that orthoptists do not instruct patients to use home-based visual acuity tests as the procedure is not covered by indemnity insurance. BIOS reference a lack of evidence-base. The new aim of the study will be to determine the validity of home-based visual acuity assessments with the possibility of providing such an evidence- base.

The study aim will be achieved by measuring the visual acuity in the outpatient clinic as per standard of care and asking the parent or carer to use the iPAD to test visual acuity at the same visit

Inclusion Criteria:

• Age under 10 years
• Able to complete a subjective visual acuity test

Exclusion Criteria:

• Parent or carer not willing to participate in the study and give written informed consent

IPD available upon request to Daniel Osborne (d.osborne@soton.ac.uk)