Anisometropic amblyopia where patching is not happening
A 6-year-and-4-month-old boy is reviewed in the paediatric clinic. Left eye acuity is 6/38 (logMAR 0.80) with full-time spectacle wear that has been verified for 16 weeks; the right eye is 6/6. Cycloplegic refraction is +1.50 DS right and +4.75/−1.25 × 180 left; the glasses are correct and he wears them all day. At diagnosis 16 weeks ago the left acuity was 6/60, so there has been measurable improvement. Stereoacuity is 200 seconds of arc on the Frisby test. There is no strabismus, no ocular pathology and the fundi are normal. Two hours of daily patching was prescribed; his mother reports actual wear of about 30 minutes on three days a week. He becomes distressed and removes the patch, and has eczema around the left periorbital skin. Both parents work full-time, and he attends a school that has a nurse on site for 2 hours each day. School vision screening is scheduled in 3 months.
1. Has spectacle correction alone failed? Would you change treatment now, or continue as is?
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Spectacle correction has not yet failed.
- Anisometropic amblyopia commonly continues to improve on glasses alone for 18–24 weeks and sometimes longer, and this child has moved from 6/60 to 6/38 in 16 weeks. That is a real, measured response.
- 'Failure' of refractive treatment means acuity has stopped improving - conventionally, no further improvement across two consecutive visits about 8 weeks apart, with documented full-time wear.
So the correct action is neither to abandon glasses nor to assume the job is done: book an 8-week review, repeat acuity with the same chart and the same tester, and re-verify spectacle wear at school.
Two things nonetheless justify planning the next step now rather than at the point of plateau:
- Adherence to patching is roughly 90 minutes a week against a prescribed 14 hours, so the amblyopic eye is effectively untreated, and periocular eczema makes adhesive patches genuinely unpleasant. The current plan is failing on adherence even though the refraction is working.
- Discussing atropine at this visit means penalisation can start immediately at the 8-week review if acuity has plateaued, without losing another month.
Continue glasses, verify wear, document the 8-week review and counsel on pharmacological penalisation as the likely next step.
2. Atropine penalisation versus patching in this specific child - what would you choose, and what practical problems would you anticipate?
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Atropine 1% one drop daily to the right (sound) eye is the better first-line choice here.
Why it fits this child:
- The barrier to patching is behavioural and dermatological, not optical, and atropine removes both - no adhesive on eczematous skin and no negotiation with a distressed 6-year-old.
- He is a hyperope (+1.50 DS) fully corrected for distance, so atropine abolishes accommodation and blurs the sound eye at near while leaving useful distance vision: exactly the penalisation needed for school-age near work.
- One drop daily can be supervised by the school nurse and by parents, which suits a two-working-parent household.
- Trial evidence shows atropine is at least as effective as patching for moderate amblyopia, which is the range this child is in.
Anticipated problems, and how to manage them:
- Photophobia and near blur on waking - a hat and sunglasses, and warn the school.
- Reverse amblyopia - the sound eye can lose acuity, so both eyes must be measured at every visit.
- Off-label use - document the consent discussion.
- It is a cholinergic antagonist: occlude the punctum after instilling, wash hands, and keep the bottle out of the child's reach.
- The amblyopic eye has a −1.25 D cylinder, so check whether near vision in the sound eye is blurred enough; if not, consider a near add over that eye. Bangerter foil is an alternative if atropine is refused, but adherence is likely to be no better than with the patch.
3. What monitoring schedule, stopping rules and counselling would you give the family?
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Monitoring: visual acuity of each eye separately, same chart and same tester, 2–4 weeks after starting atropine and then every 6–8 weeks. Check for reverse amblyopia (a fall of one line or more in the sound eye) at every visit; if it occurs, stop atropine in that eye briefly and reduce frequency.
Success: the amblyopic eye improving towards 6/9–6/7.5, or a two-line gain with stable stereoacuity.
Stopping: reduce to part-time (weekends only) or stop when the amblyopic acuity is within one line of the fellow eye and stable across two visits, or when there has been no improvement across two consecutive visits. Do not stop abruptly without a maintenance plan.
Recurrence: roughly a quarter of children regress within the first year after stopping, more so if the initial deficit was large or treatment stopped the moment acuity equalised. Review 3 months after stopping, then 6-monthly for a year, and restart if acuity drops.
Counselling: atropine stings and makes the eye red; the child may be photophobic for several hours, so use a hat and warn the school. The drop is unlicensed for this indication, so consent should be documented. Emphasise hand-washing after instillation and safe storage.
The 3-month school screening is not a substitute for clinic review - write to the school nurse with the diagnosis, the treated eye and the plan, so that a screening 'fail' is interpreted correctly rather than triggering unnecessary referral.