Non-surgical management with prisms and vision therapy improved divergence amplitudes and reduced esodeviation in 79% of patients with acute acquired comitant esotropia, according to a retrospective cohort study published in PLOS One.
Researchers reviewed records of patients with non-accommodative, non-neurologic acute acquired comitant esotropia (AACE) (Type I or II under a newer classification system) managed between January and October 2023, at a tertiary eye care center in India. Patients with accommodative, decompensated, neurologic, cyclic, or secondary forms of AACE were excluded.
Of 34 patients evaluated, 14 completed vision therapy exercises and follow-up and were included in the analysis. All 14 had Type II AACE. Mean age was 22 years (range, 10–37), and 64% were male. Mean distance esodeviation was 28 prism diopters. Lag of accommodation was documented in 12 patients; accommodative spasm was not observed.
Management Protocol
Patients with constant diplopia were prescribed Fresnel prisms, often split between both spectacle lenses to reduce blur and facilitate tapering. The smallest prism magnitude that aided fusion at distance and near was prescribed. One patient chose ground prisms for cosmetic reasons.
All patients underwent divergence-focused vision therapy, either in-office (45-60 minutes per session, typically about 10 sessions) or home-based, centered on exercises such as Brock string, vectograms, double aperture rule, and dichoptic training using a computerized vision therapy system.
Primary outcomes were changes in negative fusional vergence (divergence amplitude) and esodeviation, measured with and without prism specatacles, before and after therapy. Measurements were obtained for both distance (3 m) and near (40 cm).
Effect on Esodeviation and Divergence
Five of 14 patients (36%) with distance esodeviation of 12–20 prism diopters (PD) and intermittent diplopia achieved stable binocular single vision with vision therapy alone and did not require prisms.
Nine patients (64%) required prism correction for constant diplopia, all with distance esodeviation of 20 PD or greater. After vision therapy, prism magnitude was reduced in four patients and eliminated in two. Three patients (21%) required full initial prism correction at the end of therapy, and one later opted for surgery.
Across all 14 patients, distance esodeviation decreased by a median of about 7 prism diopters and near deviation by about 6 prism diopters after therapy. Divergence amplitudes also improved, increasing by about 7 PD at distance and 8 PD at near.
No patient reported diplopia after therapy with or without prism correction. The longest documented follow-up was 1 year, during which improved binocularity was maintained with Brock string exercises and prism spectacles.
Subgroup Observations
In this cohort, esodeviation of 20 PD or less was typically managed with vision therapy alone. Patients with deviations up to 25 PD could, in some cases, have prisms tapered after therapy. Larger deviations were managed with combined prism and vision therapy, though some residual esodeviation persisted.
Among the broader 34-patient cohort, 68% were male. In the 14-patient analytic group, 71% had myopic refractive error.
Mean daily digital device use was approximately 7 hours. Seven of nine patients reported habitual smartphone use in the supine position.
Study Limitations
The researchers noted several limitations, including the retrospective design, incomplete documentation for some variables, heterogeneity in therapy modality and duration, and lack of a control group. Natural disease progression was also not assessed in untreated patients.
“In conclusion, non-accommodative, non-neurologic types of AACE can be managed non-surgically through a combination of prisms and/or vision therapy in 79% of patients,” the researchers wrote, adding that divergence ranges can be improved and esodeviation can be reduced with this management approach.
Disclosures: The study was funded by the Hyderabad Eye Research Foundation. The researchers declared no competing interests.
Source: PLOS One
