Bilateral Refractive Amblyopia Treatment Study

• To determine the amount of visual acuity improvement with treatment of presumed bilateral refractive amblyopia
• To determine the time course of visual acuity improvement with treatment

There is a paucity of literature on bilateral amblyopia that is due to a substantial amount of refractive error (hypermetropia or astigmatism), and it is limited principally to review articles and case reports. The incidence is not known, but in one study, 4 of 830 (0.5%) children examined at the time of entry into school had bilateral amblyopia. Schoenleber et al performed a retrospective review of office records and identified 184 children with > +4.00 diopters of hypermetropia in both eyes, 12 of whom (6.5%) had bilateral amblyopia of 20/50 or worse. Ten of the 12 children (83%) improved to 20/40 or better in both eyes over a mean follow-up time of 22 months. Werner and Scott reported 6 cases of bilateral hypermetropic amblyopia with a spherical equivalent of at least +5.00 D and an initial visual acuity of 20/40 or worse in both eyes. All 5 patients with follow up improved with glasses alone, and 2 of these 5 had a most recent visual acuity worse than 20/40 in one eye with follow-up less than one year. Cavazos et al identified 218 eyes with hyperopia > +5.00 D or astigmatism >+2.00 D. Of these, 82 (38%) of the dominant eyes had an initial corrected visual acuity less than 20/25. Most improved to > 20/25, but many patients were lost to follow-up. In ongoing studies, bilateral refractive amblyopia is being evaluated in Native Americans.

1. Patients will be enrolled who have bilateral refractive error with hyperopia >+4.00 D and/or astigmatism >2.00 D and have visual acuity in each eye, measured using best correction derived from cycloplegic refraction, meeting the following criteria:

1. Age 3 to <11 years
2. Able to perform single-surrounded single optotype visual acuity using the ATS HOTV protocol for children 3 to <7 years old and using the E-ETDRS protocol for children 7 to <11 years old
3. Monocular visual acuity in each eye, measured using trial frames or phoropter with best correction derived from cycloplegic refraction, meeting the following criteria:

No longer recruiting. Comments: Recruitment started August 2004.

Completed, with results published. Comments: The study was completed in July 2006.

Mean binocular visual acuity improved from 0.50 logarithm of the minimum angle of resolution (logMAR) units (20/63) at baseline to 0.11 logMAR units (20/25) at one year (mean improvement, 3.9 lines; 95% confidence interval [CI], 3.5 to 4.2). Mean improvement at one year for the 84 children with baseline binocular acuity of 20/40 to 20/80 was 3.4 lines (95% CI, 3.2 to 3.7) and for the 16 children with baseline binocular acuity of 20/100 to 20/320 was 6.3 lines (95% CI, 5.1 to 7.5). The cumulative probability of binocular visual acuity of 20/25 or better was 21% at five weeks, 46% at 13 weeks, 59% at 26 weeks, and 74% at 52 weeks.

Treatment of bilateral refractive amblyopia with spectacle correction improves binocular visual acuity in children three to less than 10 years of age, with most improving to 20/25 or better within one year.