Anisometropic amblyopia is when one eye has a much stronger glasses prescription than the other, causing poor vision in one eye, even with glasses, because the brain favours the better-seeing eye.

With standard care treatment (glasses plus either patching or atropine drops given to the better seeing eye), 35% of children with anisometropic amblyopia do not have any significant visual improvements, and will have reduced vision in one eye for life. There is no consensus for the reasons why some children do not respond as well as others.

Recent research using the Plusoptix PowerRefractor (PR3), which quickly measures eye focusing (accommodation), suggested that in children with anisometropic amblyopia, the focusing of the amblyopic eye might influence treatment success. However, such measurements weren't previously common due to equipment limitations in clinics.

The investigators aim to use the non-invasive PR3 to assess accommodation in hypermetropic anisometropic amblyopia, at the University of Sheffield. This will be a two-phase study of children aged 4-10 years who have hypermetropic anisometropia. The investigators will recruit participants attending the Ophthalmology Department at Sheffield Children's NHS Foundation Trust (SCH). The investigators will take repeated measurements of accommodation at points during standard care treatment (phase 1) and conduct a pilot intervention study (phase 2) to determine whether adjusting glasses prescriptions based on accommodation responses with amblyopia treatment can improve vision in the weaker eye. The goal is to gather evidence to inform a future larger multicentre RCT to improve the visual outcomes for anisometropic amblyopic children in the future.

This is a two-phase study of children aged 4-10 years who have hypermetropic anisometropia:

1. Phase 1 is a cohort observational study. It will involve repeated measurements of accommodation response (using the PR3) of hypermetropic anisometropic children during their standard care treatment at SCH. PR3 measurements (all non-invasive) will be taken at various stages of their treatment to track if accommodation responses change over time.
2. Phase 2 is a pilot intervention study. It will recruit hypermetropic anisometropic children who have finished their standard care treatment at SCH but have not achieved equal (or nearly equal) vision for initial screening. Those who are found to have asymmetrical accommodation responses, and also have residual amblyopia (unequal vision in the two eyes) will be invited to the intervention study. Bespoke glasses will be issued, based on accommodation response, and children will restart occlusion (patching) for 12 weeks while wearing the bespoke glasses. This is to assess whether a glasses adaptation based on accommodation response will help to further improve vision in their amblyopic eye.

Inclusion Criteria:

Phase 1

• 4-10 years (at recruitment)
• Have hypermetropic anisometropia with ≥1.00D of difference (in spherical equivalent)
• Are currently undergoing treatment for hypermetropic anisometropia (including refractive adaptation and/or occlusion treatment - patching or atropine)
• Visual acuity in non-amblyopic eye ≤0.200 logMAR
• Any level of VA in amblyopic eye (worse than non-amblyopic eye)
• No manifest strabismus
• Accept microT with/without identity
• No other eye conditions as cause of amblyopia (e.g. stimulus deprivation amblyopia/strabismic amblyopia)
• No significant health conditions that would impact vision or accommodation response (e.g. Down's Syndrome/Cerebral Palsy)
• Informed consent from parent / guardian and assent from child (over 5 years)

Phase 2

• 4-10 years (at recruitment)
• Hypermetropic anisometropic amblyopes ≥1.00D of difference (in spherical equivalent)
• Finished standard amblyopia occlusion treatment (including patching and/or atropine)
• Asymmetric accommodation responses (Anti-A and Aniso-A) following preliminary assessment
• VA in non-amblyopic eye ≤0.200 logMAR
• Residual amblyopia (defined as interocular difference of ≥0.2 log units)
• No manifest strabismus
• Accept microT with/without identity
• No other eye conditions as cause of amblyopia (e.g. stimulus deprivation amblyopia/strabismic amblyopia)
• No significant health conditions that would impact vision or accommodation response (e.g. Down's Syndrome/Cerebral Palsy)
• Informed consent from parent / guardian and assent from child (over 5 years)

Exclusion Criteria:

Phase 1 and Phase 2

• Not within the age range 4-10 years at time of recruitment
• Has myopic anisometropia (either eye)
• <1.00D of hypermetropic anisometropia
• Vision in non-amblyopic eye worse than >0.200 logMAR
• Has a manifest strabismus
• Has amblyopia caused by an eye condition (e.g. stimulus deprivation amblyopia/strabismic amblyopia)
• Has a significant health condition that would impact vision or accommodation response (e.g. Down's Syndrome/Cerebral Palsy)
• Parent /guardian unable to give informed consent
• Parent/guardian unable to communicate in English sufficiently to give informed consent
• (Phase 2 only) does not have residual amblyopia (has equal vision in both eyes)
• (Phase 2 only) has symmetrical accommodation on the PR3 tests