Amblyopia, often referred to as “lazy eye,” is a common visual disorder that affects millions of people worldwide, particularly children. It occurs when one eye does not develop proper visual acuity, leading to reduced vision in that eye.
A growing body of research suggests that binocular therapy is becoming increasingly important in the management and treatment of amblyopia, especially after the critical period passes.
In this blog post, we will discuss the significance of binocular therapy in amblyopia treatment and why it is considered a game-changer in improving the visual outcomes for individuals with this condition.
Binocular Function and Amblyopia
Binocular vision is the ability to use both eyes together to perceive depth and three-dimensional (3D) images. It plays a pivotal role in our daily lives, enabling us to judge distances accurately, catch a ball, or read comfortably. In amblyopic individuals, the lack of coordination between the eyes can result in various visual deficits, including poor depth perception and difficulty with tasks that require both eyes to work together.
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Binocular Summation
Binocular summation refers to an improvement in a specific task when the stimuli are shown to two eyes rather than one. In amblyopia, binocular summation is commonly reported as absent or severely diminished (Hess et al., 2014).
However, research has found that normal levels of binocular summation are achieved if the signal to the amblyopic eye is increased. More specifically, if we adjust the contrast of the stimuli presented to the amblyopic eye (that it is really strong) compared to the fellow eye.
Suppression
Suppression means that the ”normal” eye restrains the function of an amblyopic eye when both eyes are viewing. Why? Many researchers assumes that the role of suppression is to block information from the weak eye so you don’t see double or get confused.
Suppression is a crucial component of the amblyopia condition, and the positive association between suppression and amblyopia depth suggests that binocular dysfunction is the fundamental issue (Hess & Thompson, 2015).
What is Dichoptic Training?
Dichoptic training is a therapeutic approach to treatment of amblyopia under binocular conditions. Dichoptic treatment relies on using red and green glasses to present separate visual stimuli to each eye. By engaging both eyes independently, this treatment method aims to improve binocular vision and enhance visual processing capabilities.
Dichoptic Training Enables the Adult Amblyopic Brain to Learn
Dichoptic training results in significantly greater learning effects than monocular training. In a study from Li et al. (2013), 9 patients played video games in monocular mode, and 9 patients in binocular (dichoptic) mode.
Only after two weeks of training for one hour per day, both groups showed significant improvement in visual acuity. However, dichoptic group led to significantly greater improvements in visual acuity than the monocular group.
Moreover, dichoptic group also experienced greater improvements in stereopsis, while monocular training had no significant improvements.
In addition, dichoptic training resulted in a large and significant reduction in suppression.
”Results of the study show that effects of the 40 hours monocular training can be achieved after just 10 hours of dichoptic training.”
Binocular Vision Therapy Benefits
Binocular vision therapy enhances general binocular function and stereo acuity by using simultaneous binocular visual stimulation (dichoptic treatment).
Binocular Therapy for Childhood Amblyopia Improves Vision Without Breaking Interocular Suppression
Bossi et al. (2017) analyzed home-based binocular treatment system for amblyopia. Their goal was to achieve high level of compliance while simultaneously allowing to investigate the role of suppression in children’s binocular treatment responses. It turned out binocular therapy for childhood amblyopia improved vision without breaking interocular suppression.
Binocular Therapy as Primary Intervention in Adults with Anisometropic Amblyopia
Murali et al. (2022) investigated the effectiveness of dichoptic training in adults with anisometropic amblyopia. As a result, BCVA and near acuity improved. Also, improvement of the stereopsis was present in 24% of attendees within the 3-months.
Binocular Therapy Improves Contrast Sensitivity in Adults
Hess and Thompson (2015) claimed that binocular stimulation improves contrast sensitivity in adults with amblyopia.
Binocular Therapy Reduces Suppression
Li et al. (2011) demonstrated that frequent exposure to dichoptic training successfully diminishes suppression in adults with amblyopia. Consequently, visual acuity and stereopsis improve.
Conclusion
Binocular therapy has emerged as a critical component of amblyopia treatment, addressing not only the visual acuity of the amblyopic eye but also stereopsis and suppression. Dichoptic training is much more effective than monocular training. Furthermore, forcing both eyes to work together results in greater brain plasticity.
Frequently Asked Questions
Binocular therapy for amblyopia, also known as “binocular vision therapy” or “binocular vision training,” is a specialized treatment approach used to improve the visual function and coordination of the eyes in individuals with amblyopia, commonly known as “lazy eye.”
Dichoptic training is a therapeutic approach to treatment of amblyopia under binocular conditions. Dichoptic treatment relies on using red and green glasses to present separate visual stimuli to each eye. By engaging both eyes independently, this treatment method aims to improve binocular vision and enhance visual processing capabilities.
Sources:
Bossi, M., Tailor, V., Anderson, E. J., Bex, P. J., Greenwood, J. A., Dahlmann-Noor, A., & Dakin, S. C. (2017). Binocular therapy for Childhood amblyopia improves vision without breaking interocular suppression. Investigative Ophthalmology & Visual Science, 58(7), 3031. https://doi.org/10.1167/iovs.16-20913
Hess, R. F., & Thompson, B. (2015). Amblyopia and the binocular approach to its therapy. Vision Research, 114, 4–16. https://doi.org/10.1016/j.visres.2015.02.009
Hess, R. F., Thompson, B., & Baker, D. H. (2014). Binocular vision in amblyopia: structure, suppression and plasticity. Ophthalmic and Physiological Optics, 34(2), 146–162. https://doi.org/10.1111/opo.12123
Li, J., Thompson, B., Deng, D., Chan, L. K., Yu, M., & Hess, R. F. (2013). Dichoptic training enables the adult amblyopic brain to learn. Current Biology, 23(8), R308–R309. https://doi.org/10.1016/j.cub.2013.01.059
Li, J., Thompson, B., Lam, C. S. Y., Deng, D., Chan, L. K., Maehara, G., Woo, G. C., Yu, M., & Hess, R. F. (2011). The role of suppression in amblyopia. Investigative Ophthalmology & Visual Science, 52(7), 4169–4176. https://doi.org/10.1167/iovs.11-7233
Murali, K., Ramesh, A., Murthy, S., & Goyal, A. (2022b). Binocular therapy as primary intervention in adults with anisometropic amblyopia. Taiwan Journal of Ophthalmology, 12(3), 317. https://doi.org/10.4103/tjo.tjo_37_21