Families often hear: "drops — if the patch doesn't work out". ATS1 and Cochrane 2019 do not say that. They say: comparable acuity gain in moderate amblyopia in preschool children, with a different profile of adherence and side effects.
How it works. Atropine penalisation: atropine sulfate in the fellow eye abolishes accommodation and produces prolonged mydriasis, so that the fellow eye performs near tasks less well, and the cortex more often takes the amblyopic channel. This is not "poison for the good eye". It is an optical-pharmacological switching-off of sharpness at a given distance.
Daily versus weekend, ATS4. In children under 7 with moderate amblyopia, weekend atropine produced a gain of the same order as daily atropine. That is why the PPP, in its highlighted findings, places side by side: 2 hours of patching or weekend atropine as the start for the moderate form. For severe amblyopia, a separate PEDIG study showed that weekend atropine can also improve acuity in preschool children with 20/125–20/400 — this is not ATS1 and should not be read as a full replacement for 6 hours at 20/400 in every child, but it is grounds for not regarding the drop as "only for mild cases".
Older children, 7–12 years. PEDIG compared 2 hours of occlusion and weekend atropine 1% at 20/40–20/100: mean gain of about 1.5 lines over 17 weeks in both groups, then up to a maximum of on average 2.2 lines — with no difference between drop and patch. After the critical period in the narrow sense, both methods remain workable in this stratum, with a smaller mean response than in preschool children.
The harm profile, which should be named aloud — not to frighten, but to choose.
- Photophobia — typical; tinted glasses, a hat.
- Mild reduction in fellow-eye acuity, more often than with the patch in ATS1; mostly reversible on stopping.
- Systemic effects are rare but not zero: the ATS materials mention facial flushing and, in isolated cases, a switch to homatropine; the PPP, in its general section on cycloplegics, lists more severe anticholinergic reactions.
- Reverse amblyopia — see Lesson 2.5.
- Adherence after an instilled drop is higher than with a patch that gets taken off: Cochrane 2019, moderate certainty.
Optical penalisation (plus lens over the fellow eye, plano lens with atropine). PPP: in studies, adding optical penalisation to atropine did not produce significantly better outcomes than atropine alone, with small samples and wide CIs; theoretically a small gain in those who stopped improving on atropine alone cannot be excluded. This is not a standard of "plano for everyone".
When atropine is particularly appropriate. The child tears off the patch; the skin does not tolerate adhesive; the social burden of patching at school breaks the regimen; penalisation that leaves the peripheral field is needed. When to be more cautious: very poor acuity in the amblyopic eye, at which even at near after atropine the fellow eye is still more convenient; unreliable follow-up visits (risk of missing reverse amblyopia); systemic contraindications to anticholinergics, which are assessed by the clinician and not by this course as a reference.
Boundary. Atropine in this lesson is penalisation of the fellow eye, not "treatment of accommodative spasm" and not a low-dose myopia protocol. Confusing 1% weekend for amblyopia with 0.01% at night for myopia is a pharmacological error belonging to another module.