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. 2017 Jul-Sep;10(3):169-175.
doi: 10.1016/j.optom.2016.10.001. Epub 2017 Jan 24.

Changes in stimulus and response AC/A ratio with vision therapy in Convergence Insufficiency

Neeraj Kumar Singh  1 , Revathy Mani  2 , Jameel Rizwana Hussaindeen  3
Affiliations

Changes in stimulus and response AC/A ratio with vision therapy in Convergence Insufficiency

Neeraj Kumar Singh et al. J Optom. 2017 Jul-Sep.

Abstract
in English, Spanish

Purpose: To evaluate the changes in the stimulus and response Accommodative Convergence to Accommodation (AC/A) ratio following vision therapy (VT) in Convergence Insufficiency (CI).

Methods: Stimulus and response AC/A ratio were measured on twenty five CI participants, pre and post 10 sessions of VT. Stimulus AC/A ratio was measured using the gradient method and response AC/A ratio was calculated using modified Thorington technique with accommodative responses measured using WAM-5500 open-field autorefractor. The gradient stimulus and response AC/A cross-link ratios were compared with thirty age matched controls.

Results: Mean age of the CI and control participants were 23.3±5.2 years and 22.7±4.2 years, respectively. The mean stimulus and response AC/A ratio for CI pre therapy was 2.2±0.72 and 6.3±2.0 PD/D that changed to 4.2±0.9 and 8.28±3.31 PD/D respectively post vision therapy and these changes were statistically significant (paired t-test; p<0.001). The mean stimulus and response AC/A ratio for controls was 3.1±0.81 and 8.95±2.5 PD/D respectively.

Conclusions: Stimulus and response AC/A ratio increased following VT, accompanied by clinically significant changes in vergence and accommodation parameters in subjects with convergence insufficiency. This represents the plasticity of the AC/A crosslink ratios that could be achieved with vision therapy in CI.

Objetivo: Evaluar los cambios de la relación convergencia acomodativa/acomodación (AC/A) estímulo y respuesta, tras terapia visual (TV) en casos de Insuficiencia de Convergencia (CI).

Métodos: Se midieron las relaciones AC/A de estímulo y respuesta en veinticinco participantes, tras realizar sesiones previas y posteriores de TV. La relación AC/A de estímulo se midió utilizando el método gradiente, y la relación AC/A de respuesta se calculó utilizando la técnica modificada de Thorington, midiendo las respuestas acomodativas con un autorrefractómetro de campo abierto WAM-5500. Se compararon las relaciones cruzadas AC/A gradiente estímulo y respuesta con treinta controles emparejados por edad.

Resultados: La edad media del grupo con CI y el grupo control fue de 23,3 ± 5,2 años y 22,7 ± 4,2 años, respectivamente. La relación media AC/A de estímulo y respuesta para CI previa a la terapia fue de 2,2 ± 0,72 y 6,3 ± 2 PD/D, cuyos valores fueron de 4,2 ± 0,9 y 8,28 ± 3,31 PD/D respectivamente tras la terapia visual. Dichos cambios fueron estadísticamente significativos (prueba de t pareada; p < 0,001). La relación media AC/A de estímulo y respuesta para los controles fue de 3,1 ± 0,81 y 8,95 ± 2,5 PD/D.

Conclusiones: La relación AC/A de estímulo y respuesta se incrementó tras la TV, junto a cambios clínicamente significativos en lo que respecta a vergencia y parámetros de acomodación en los pacientes con insuficiencia de convergencia. Esto representa la plasticidad de las referencias cruzadas AC/A, que podría alcanzarse con terapia visual en los casos de CI.

Keywords: Accommodative convergence to accommodation ratio; Convergence Insufficiency; Insuficiencia de Convergencia; Relación acomodación/convergencia acomodativa (AC/A); Terapia visual; Vision therapy.

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