Optometry & Visual Performance 259 Volume 13 | Issue 4 | December 2025 that vision therapy can be effective in managing esodeviation.18 Vision therapy for DI is quite challenging;16 this was discussed with of all the patients. Vision therapy for these patients was structured in accordance with the treatment guidelines for DI.16 In this case series, the objective of vision therapy was to eliminate diplopia if present, enhance sensory and motor fusion, reduce the frequency of deviation, and maintain binocularity. In all three patients, therapy started at near, where the patients were comfortable and successful, and gradually increased to the distance. Additionally, peripheral fusional targets were introduced first, followed by the use of central targets. Vision therapy may also be necessary with the combination of base-out prism for the management of DI, as in this case series. The amount of prism can be determined using several methods, such as Sheard’s criterion, fixation disparity analysis, and Percival’s criterion.16 However, in this case series, we prescribed the minimum amount of prism needed to maintain fusion and eliminate diplopia. Occasionally, this prism successfully relieves the patient’s symptoms at distance but may cause discomfort at near when worn full-time. If the patient’s positive fusional vergence at near is inadequate, they may not tolerate the prism for near activities.16 When all vision therapy objectives have been achieved, therapy can be discontinued.16 Determining the endpoint of vision therapy in these types of cases is crucial, as there is a risk of rebound. When to discontinue active therapy is primarily determined by the amplitude of negative fusional vergence and the frequency of the deviation. If the patient remains asymptomatic and the fusional vergence reserve is sufficient to control the deviation while meeting Percival’s criterion,16 therapy may be discontinued. Therefore, evaluations should be conducted after each week of therapy sessions and at every follow-up. While all three cases were successful, there are some limitations. The prism prescriptions were not standardized; we chose the minimum amount of prism needed to eliminate double vision using a trial-based approach. Second, long-term followup was not conducted to observe for any rebound effect or regression. Third, distance stereoacuity was not assessed, which could help to evaluate the effectiveness of the treatment and overall binocular visual function. Conclusion Vision therapy is a non-surgical treatment approach for DI and offers an effective and promising alternative to surgical intervention. This case series demonstrates that vision therapy is a viable option and can provide positive results. 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