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  • Subthreshold Amblyopia

    By Lynda Seminara
    Selected by Richard K. Parrish II, MD
    Pediatric Ophth/Strabismus
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    Journal Highlights

    American Journal of Ophthalmology, July 2023

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    While compiling a database of patients with amblyopia who visited Boston Children’s Hospital during a five-year period, Michalak et al. noted that a substantial number of cases did not meet the VA threshold for this disorder. The authors found that although most 12-month treatment outcomes were un- remarkable for patients with “subthreshold amblyopia,” nearly half of them subsequently had 20/20 vision in both eyes, as well as stereopsis improvement.

    Included in the analysis were 2- to 12-year-olds who had a new diagnosis of amblyopia between 2010 and 2014. BCVA was better than 20/40 in at least one eye but was not correctable to 20/20; no patient had a structural abnormality. The main outcome measure was ambly­opia resolution, defined as VA of 20/20 or better in both eyes.

    Among 2,311 new diagnoses of am­blyopia, 464 (20.1%) were considered subthreshold. The median age of this subgroup was 6.3 years, and 49.6% were female. Nearly 62% had an amblyogenic factor, and the remainder did not meet the quantitative criteria for amblyopia. Almost all subthreshold cases (97.5%) received treatment, consisting of eye­glasses (94%), patching (38%), and/or atropine (6%).

    Approximately 69% of the subthreshold cohort returned for follow-up (me­dian time, 3.1 years). Twenty percent experienced full resolution within 12 months. By the final visit, resolution was complete in 152 patients (47.8%); this included five of eight patients who received observation only. Among those with complete resolution, median stereopsis improved from 4.50 (first visit) to 3.91 (final visit).

    In the univariate analysis, factors correlating with amblyopia resolution were longer follow-up time, no previous amblyopia treatment, no mechanism meeting amblyopia criteria, better log stereopsis at initial and final visits, and greater self-reported use of glasses. In the multivariate analysis, the only factor with a significant link to resolved subthreshold amblyopia was longer du­ration of follow-up (OR, 1.38; p < .001), indicating that this cohort may benefit from extended monitoring and extra encouragement to adhere to treatment.

    Most studies of amblyopia involved patients with worse baseline VA; hence, information on the management and outcomes of subthreshold amblyopia is lacking. The authors recommend research to explore the natural history of subthreshold amblyopia and to de­termine whether good outcomes can be achieved by observation alone.

    The original article can be found here.