A myth that PEDIG spent two decades dismantling: severe amblyopia must be patched all waking hours, moderate amblyopia "a lot". The hours prescribed in trials are not necessarily the hours worn, but it was the prescribed regimen that was compared, and it is the prescribed regimen that the PPP carries into practice.
Moderate amblyopia (20/40–20/80), children under 7 years, ATS2B. 189 children, 2 hours versus 6 hours a day, 4 months. Mean gain identical — 2.40 lines in each group (P = 0.98). At 4 months acuity was 20/32 or better and/or improved by ≥3 lines in 62% in each group; this is the level after treatment, not the entry criterion: at entry there was moderate amblyopia of 20/40–20/80. The proportion with a gain of ≥2 lines from baseline was 79% with 2 hours and 76% with 6. PPP highlighted: most children with moderate amblyopia of 20/40–20/80 respond to initial therapy with 2 hours of daily patching or weekend atropine.
Severe amblyopia (20/100–20/400), under 7 years, ATS2A. 175 children, 6 hours versus near full-time (all waking hours minus one). Gain 4.8 versus 4.7 lines, comparable. 6 hours here is not "greed", but a regimen that did not lose to full-time in this RCT.
Occlusion versus atropine, ATS1, already discussed: 3.16 versus 2.84 lines at 6 months in 419 children under 7 with moderate amblyopia; clinically comparable. Cochrane, Li 2019 (CD006460.pub3, 7 studies, 1177 amblyopic eyes, search date 7 September 2018): atropine penalisation is as effective as conventional occlusion in improving acuity; a formal meta-analysis was not performed because of the clinical heterogeneity of the regimens. At 6 months most participants (363/522) came from ATS1, at low risk of bias, MD 0.03 logMAR (95% CI 0.00–0.06). At 24 months there is no meaningful difference (moderate certainty). Alignment, stereopsis, fellow-eye acuity — no difference (moderate certainty). Atropine — better adherence and quality of life (moderate), more photophobia and mild reduction in fellow-eye acuity not requiring treatment (high certainty). Skin/lid/conjunctival problems — more frequent with the patch (high). Atropine is cheaper.
How to patch technically. PPP: an opaque adhesive patch on the skin around the fellow eye, glasses on top. Cloth on the frame is worse: children look around it. Reverse amblyopia is rare at current doses, but the fellow eye is measured at every visit. Skin irritation in ATS1: mild in 41%, moderate or severe in a further 6%. A child in a patch must not be left unsupervised near stairs and roads. Family education improves adherence (PPP, rating I+, Good, Strong).
Bangerter filters. ATS13 (PEDIG, Rutstein et al., Ophthalmology 2010): 186 children aged 3–<10 years, moderate amblyopia 20/40–20/80, a filter on the fellow-eye lens versus daily occlusion, 24 weeks. Gain 1.9 versus 2.3 lines; the upper bound of the one-sided 95% CI, 0.76 lines, slightly exceeded the pre-specified non-inferiority limit of 0.75. The proportions with ≥3 lines and with acuity ≥20/25 did not differ. The burden on the family on the Amblyopia Treatment Index was lower with the filter. The authors and the PPP consider the filter a reasonable option for starting treatment of moderate amblyopia, despite the formally unmet non-inferiority criterion.
Cochrane, Taylor 2014 on strabismic amblyopia: occlusion plus the necessary glasses is better than glasses alone (MD −0.18 logMAR). The review considers the addition of "near work" as a mandatory ritual unconvincing.
Boundary. These doses were obtained in children mainly aged 3–<7 years with strabismic, anisometropic or combined amblyopia, not in an infant with deprivation and not in an adult. Transferring "2 hours" to dense unilateral aphakia at eight weeks is not a reading of ATS2B. Deprivation amblyopia, the PPP writes, is difficult, and the regimen there is individual once the axis has been cleared.