Amblyopia and Suppression

Thank you to COVD for writing this piece. COVD Link:

Our guest blogger is Marsha Sorenson, OD. Dr. Sorenson is a graduate of the Illinois College of Optometry and completed her residency in vision therapy and rehabilitation at SUNY College of Optometry. Dr. Sorenson is currently a staff optometrist at the Chicago Public Schools vision clinic, where she supervises optometry students and provides vision therapy services.  She also practices at Chicago Dizziness and Hearing clinic, where she provides vision therapy services for patients with vestibular disorders and brain injury.

Amblyopia, a visual condition more commonly known as lazy eye, is diagnosed as a reduction in visual acuity in one or both eyes in the absence of disease. Amblyopia is most commonly caused by anisometropia (a higher prescription in one eye) orstrabismus (an eye turn). Amblyopia is typically treated with glasses and patching the “good” eye. However, many children dislike wearing the patch and rip it off. But there’s good news for kids and adults with amblyopia- new research is showing that using computerized games to reduce suppression is an effective treatment option!

When someone has amblyopia, their brain suppresses, or turns off, the amblyopic eye’s image, and relies on information from the good eye. This reduces an amblyopic person’s depth perception. Optometric vision therapy techniques to reduce suppression and improve 3-D vision have been around for a long time, but until recently there hasn’t been much scientific evidence to support these treatment techniques.

Vision scientists found a new way to measure suppression- by reducing contrast to the dominant, or “good” eye until both eyes are being used equally. Several researchers found that stronger suppression was associated with worse visual acuity in the amblyopic eye. Researchers then compared levels of suppression to patching outcomes, and discovered children with higher levels of suppression did not respond as well to patching therapy. Vision therapy to reduce suppression may be a better treatment option for patients with high levels of suppression. Video games with reduced contrast displayed to the dominant eye are being evaluated as a new treatment option for amblyopia. In preliminary studies, these video games have improved vision in both children and adults- and at a much faster rate than the typical patching treatment. Many patients improved their depth perception- and a few even saw in 3D for the first time!

Vision therapy is a great amblyopia treatment option because it treats all the weaknesses of the lazy eye, not just the reduction in visual acuity. Amblyopic eyes also have difficulty tracking, focusing, and processing visual information. The amblyopic visual system also has reduced depth perception. Vision therapy retrains pathways in the brain to improve vision the amblyopic eye, and teaches the brain to use both eyes together as a team.

This research is very exciting news for children and adults with amblyopia. Historically, amblyopia was not treated in adults because scientists believed neuroplasticity did not exist in the adult brain, and clinical trials of patching in adults did not show much improvement in visual acuity. Attempting amblyopia treatment in adults is worthwhile because the good eye is at an increased risk for injuries and eye disease. 3-D vision helps us make spatial decisions in world around us, which is important for everyday tasks like driving, walking, and reaching for objects.

The Pediatric Eye Disease Investigator Group (PEDIG) has been conducting randomized clinical trials evaluating the effectiveness of variable contrast anti-suppression video game therapy. The results of their ongoing research could significantly influence future amblyopia treatment guidelines.

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