Two-Eye Training Superior to One for Amblyopia

Dichoptic training for amblyopia (lazy eye) in adults resulted in significantly greater improvement compared with monocular training, according to a new study.

Researchers at McGill University (Montreal, Canada) recruited 18 adults with amblyopia into a randomized comparison of dichoptic versus monocular training involving the video game Tetris. The patients were randomized to daily 1-hour sessions of playing the game monocularly or dichoptically; after 10 sessions, patients in the monocular group crossed over to dichoptic training for an additional 10 sessions. During dichoptic training standard stimulus elements were presented separately to each eye, and lower-contrast stimuli were also presented to the fixing eye to offset suppression and facilitate binocular combination of the stimuli.

At the end of the first period, patients in both groups had significant improvement in visual acuity, but dichoptic learning resulted in a four-fold improvement. After crossover to dichoptic training, the monocular group also improved visual acuity by a factor of four as compared with the first sessions. Dichoptic training also improved stereopsis (depth perception) by a factor of four, whereas monocular training had no effect. Again, after crossover to dichoptic training, stereopsis improved significantly in the monocular group. Dichoptic training also led to a significant reduction in suppression. The study was published in the April 26, 2013, issue of Current Biology.

“This strongly suggests that suppression of the amblyopic eye gates plasticity within the adult amblyopic visual cortex,” concluded lead author Robert Hess, PhD, DSc, and colleagues. “By directly reducing suppression, learning was enabled and significant improvements in both monocular and binocular visual function occurred, although visual function did not recover to normal levels. This provides a basis for the treatment of amblyopia in adults who currently have no treatment options.”

Amblyopia is an eye disorder characterized by an impaired vision in an eye that otherwise appears normal. Visual stimulation either fails to transmit or is poorly transmitted through the optic nerve to the brain for a continuous period of time. It can also occur when the brain "turns off" the visual processing of one eye to prevent double-vision, for example in strabismus. Detecting the condition in early childhood increases the chance of successful treatment, especially if detected before the age of five.


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