Characterization of Bangerter filter effect in mild and moderate anisometropic amblyopia: predictive factors for the...

To evaluate the outcome achieved by using Bangerter filters in cases of mild and moderate anisometropic amblyopia, and to define the predictive factors for the final visual outcome.

Prospective study comprising 62 children (age range 3-11 years) with unilateral amblyopia associated with myopic or hyperopic anisometropia. In all cases, the use of Bangerter filters were prescribed for amblyopia treatment due to the unsuccessful outcome with refractive correction. The prescribed filter always induced a visual acuity reduction in the non-amblyopic eye of 2 lines below the BSCVA of the amblyopic eye. A follow-up of 12 months was completed.

A statistically significant improvement in visual acuity was observed at 3 months in both groups, amblyopic and non-amblyopic eyes (p < 0.01). At 6, 9 and 12 months, additional small but statistically significant improvements in visual acuity were detected only in the amblyopic group (p ≤ 0.02). Filter density had to be changed during the follow-up in a total of 22 eyes (35.5%). A significant correlation of the visual acuity with the baseline interocular visual acuity difference was found at 3 months (r = 0.44, p < 0.01), but not at the end of the follow-up (r = 0.12, p = 0.36). Multiple linear regression analysis revealed that the final visual outcome was significantly correlated with the baseline visual acuity, sphere and the difference in visual acuity between eyes (R²: 0.42, p < 0.01).

Bangerter filters are useful for treating mild or moderate amblyopia due to anisometropia, but ocular dominance inversion should be maintained during treatment for obtaining an optimized outcome.