Optical treatment of strabismic and combined strabismic-anisometropic amblyopia

Abstract

Objective: To determine visual acuity improvement in children with strabismic and combined strabismic-anisometropic (combined-mechanism) amblyopia treated with optical correction alone and to explore factors associated with improvement.

Design: Prospective, multicenter, cohort study.

Participants: We included 146 children 3 to <7 years old with previously untreated strabismic amblyopia (n = 52) or combined-mechanism amblyopia (n = 94).

Methods: Optical treatment was provided as spectacles (prescription based on a cycloplegic refraction) that were worn for the first time at the baseline visit. Visual acuity with spectacles was measured using the Amblyopia Treatment Study HOTV visual acuity protocol at baseline and every 9 weeks thereafter until no further improvement in visual acuity. Ocular alignment was assessed at each visit.

Main outcome measures: Visual acuity 18 weeks after baseline.

Results: Overall, amblyopic eye visual acuity improved a mean of 2.6 lines (95% confidence interval [CI], 2.3-3.0), with 75% of children improving ≥ 2 lines and 54% improving ≥ 3 lines. Resolution of amblyopia occurred in 32% (95% CI, 24%-41%) of the children. The treatment effect was greater for strabismic amblyopia than for combined-mechanism amblyopia (3.2 vs 2.3 lines; adjusted P = 0.003). Visual acuity improved regardless of whether eye alignment improved.

Conclusions: Optical treatment alone of strabismic and combined-mechanism amblyopia results in clinically meaningful improvement in amblyopic eye visual acuity for most 3- to <7-year-old children, resolving in at least one quarter without the need for additional treatment. Consideration should be given to prescribing refractive correction as the sole initial treatment for children with strabismic or combined-mechanism amblyopia before initiating other therapies.

Financial disclosure(s): The authors have no proprietary or commercial interest in any of the materials discussed in this article.

Figure 1. Visit Completion

*Ineligible due to: improper method of evaluating visual acuity at screening (3), no measureable heterotropia at screening by Simultaneous Prism and Cover Test (8), no longer meeting eligibility requirement for visual acuity at baseline (20), and use of spectacles or other amblyopia treatment prior to baseline (4) ** Children who improved one or more lines from baseline were eligible to continue after 18-week primary outcome with visits every 9 weeks until no further improvement

Figure 2. Amblyopic Eye Visual Acuity Over Time

For each visit, the box on the left (gray) is the distribution of amblyopic eye visual acuity (in logarithm of minimum angle of resolution) for children with combined-mechanism amblyopia, while the box on the right (white) represents children with strabismic-only amblyopia. The top and bottom of each box represent the 25^th and 75^th percentiles of the data, the group medians are represented by the middle line in each box, and the group means are represented by a dot. The bars extending above and below each box represent 1.5 times the interquartile range (difference between the 25^th and 75^th percentiles). The open circles represent individuals whose values are statistical outliers. logMAR = logarithm of the minimum angle of resolution