APR 08, 2016
This retrospective review shows similar stereoacuity outcomes after treatment with bifocals or single-vision glasses in 180 patients with a high accommodative convergence/accommodation (AC/A) ratio.
Prescribing bifocals to esotropic children with residual near alignment deviations is common practice for improving overall stereopsis. However, this research failed to find any benefit of bifocal therapy over single-vision hyperopic correction.
Of the 77 children in the bifocal cohort, the authors found a surgical intervention rate of 16%, compared to 4% for the single-vision group (P=0.04). Additionally, bifocal wearers had a higher distance deviation at final follow-up than single-vision lens wearers, after adjustment for initial near deviation, age, and initial distance deviation (P=0.02).
Investigators also conducted a subgroup analysis to compare outcomes between the phoric bifocal group (phoric at near through the bifocal) and the phoric single-vision group (phoric at near through +3.00 D add) and found no difference between bifocals and single-vision lenses in stereopsis improvement, final stereopsis or final near or distance deviation.
The authors propose a hypothesis to explain their results. They speculate that “binocular experience at distance with variable deviation at near… may drive sustained fusional divergence to decrease the near deviation and maintain some degree of binocularity in everyday life…. Single-vision wearers thus might ‘learn’ to control their deviations over a range of distances more effectively.”
Bifocals are more expensive than single-vision lenses and some children have difficulty accepting and wearing them. Even when properly made, a bifocal can interfere with a child’s regular activity, making normal children seem clumsy when on the playground or walking down steps. Though the authors conclude that more study is required to determine if single-vision glasses are at least as good as bifocals, these findings have the potential to save considerable health care dollars and spare children the struggle of bifocals.