Patients with sensory eye dominance may be able to improve their fine depth perception, according to a new study in the October issue of Current Biology. Researchers were able to balance participants’ vision using a push-pull training method, in which the weaker eye was stimulated while the function of the stronger eye was suppressed. So, instead of the traditional patching method, in which an opaque eye patch is used on the stronger eye to force the weak eye to function better, this new vision therapy aims to reduce sensory eye dominance by making the eyes compete for perception.
“In sensory eye dominance, the inhibitory interaction between the two eyes is unbalanced. Therefore, to reduce sensory eye dominance, one has to address the inhibitory mechanism,” says study author Teng Leng Ooi, Ph.D., of the Pennsylvania College of Optometry at Salus University.
Dr. Ooi explains that the novel push-pull method works because both eyes are stimulated in opposite ways. “For example, the weak eye is stimulated with vertical grating, and the strong eye with horizontal grating. During the push-pull training, we attract exogeneous visual attention to the weak eye to cause its stimulus (vertical grating) to be consciously perceived,” she says. “This causes the visual pathway of the weak eye to be excited (push). At the same time, the strong eye is inhibited because its stimulus (horizontal grating) is suppressed from conscious perception (pull),” explains Dr. Ooi.
Further research is needed to determine the implications of this study on conditions such as amblyopia. However, Dr. Ooi and her co-authors, Zijiang J. He, Ph.D., and graduate student Jingping J. Xu, are optimistic.
“There are reasons to believe that if implemented as an amblyopic treatment, the improvement can be stronger owing to the fact that the adolescent brain has a greater capacity to change,” says Dr. Ooi.
This treatment would be a welcome addition in amblyopia therapy, she says, because many patients discontinue wearing an eye patch because it’s not only inconvenient but also causes self-esteem issues, especially in children and adolescents.
Xu JP, He ZJ, Ooi TL. Effectively reducing sensory eye dominance with a push-pull perceptual learning protocol. Curr Biol. 2010 Oct 26;20(20):1864-8.