April 30, 2008 (Fort Lauderdale) — A new study on amblyopia has found that binocular connections remain intact — a finding that could pave the way for a new type of treatment that would be an alternative to eye patching, the current standard of care.
"We are really struggling with the way amblyopia is treated today. Patching is really hard for kids,” lead author Bahzad Mansouri, a postdoctoral student at McGill University, Montreal, Canada, told Medscape Ophthalmology. In addition to this binocular connection making treatment more palatable, he noted, it would also be preferable over current treatments because when the eye is patched, binocular vision is eliminated. "But binocular vision is very important for seeing," he said.
At present, it is assumed that patients with amblyopia lack binocular connections; therefore, treatment for the condition centers on the restoration of monocular function through the use of suppressive interocular interactions. The objective of this new study, presented here at the Association for Research in Vision and Ophthalmology 2008 Annual Meeting, was to determine the extent to which binocular connections are intact and to perform an experiment demonstrating the use of these connections in treatment.
The researchers tested 8 amblyopic and 8 normal subjects in the main experiment and also conducted a pilot treatment experiment on 2 amblyopic subjects.
First, the researchers assessed binocular vision. Using a dichoptic motion task to assess dorsal function and a dichoptic form task to assess ventral function, they were able to separate the signal and noise between the 2 eyes and to directly evaluate how well the organs combined the information. When comparable information was presented to each eye, amblyopic eyes made only a minor contribution to binocular performance. However, by reducing the information content to the fellow eye, the researchers were able to create a condition under which the 2 eyes equally combined the information.
In the pilot treatment experiment, strabismic subjects were tested for 8 weeks with an individually tailored motion task that was designed to stimulate the amblyopic eye. Findings for this experiment showed that the optotype acuity for subjects improved from 20/600 and 20/63 in the amblyopic eyes to 20/125 and 20/40, respectively. Binocular vision was also improved.
The researchers concluded that binocular connections in amblyopia are weak but intact and are able to be strengthened.
The next step, Mr. Mansouri said, is to conduct a trial comparing the new treatment with the traditional one. If the results hold up, it is possible that new treatments, such as games for children to play that incorporate vision training, could be created.
"This is a very promising approach," said Martin J. Steinbach, PhD, director of ophthalmology research at the University of Toronto, Canada, who was not involved in the study. "It's novel because it's looking at what traditionally has been described as a monocular condition, but is a binocular condition, and it opens up a new way of treating rather than putting a patch over 1 eye. Long-term follow-up research is needed to show if the improvement lasts," he added. "But this is very promising."
The study was funded by the Canadian Institutes of Health Research. The authors have applied for a patent for this finding.
Association for Research in Vision and Ophthalmology 2008 Annual Meeting: Abstract 2594. Presented April 29, 2008.
Calgary Vision Therapy Note:
Developmental optometry has known amblyopia is a binocular dysfunction and that patching one eye for extended periods of time may not correct the underlying problem that contributed to the development of the lazy eye, and that optometric vision therapy can improve visual function and visual skills in both the amblyopic and non-amblyopic eye.
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