It has been established that in amblyopia, information from the amblyopic eye (AME) is not combined with that from the fellow fixing eye (FFE) under conditions of binocular viewing. However, recent evidence suggests that mechanisms that combine information between the eyes are intact in amblyopia. The lack of binocular function is most likely due to the imbalanced inputs from the two eyes under binocular conditions [Baker, D. H., Meese, T. S., Mansouri, B., & Hess, R. F. (2007b). Binocular summation of contrast remains intact in strabismic amblyopia. Investigative Ophthalmology & Visual Science, 48(11), 5332-5338]. We have measured the extent to which the information presented to each eye needs to differ for binocular combination to occur and in doing so we quantify the influence of interocular suppression. We quantify these suppressive effects for suprathreshold processing of global stimuli for both motion and spatial tasks. The results confirm the general importance of these suppressive effects in rendering the structurally binocular visual system of a strabismic amblyope, functionally monocular.

No abstract

The results indicate that strabismic amblyopes have mechanisms for binocular summation of contrast and that the amblyopic deficits of binocularity can be simulated with an ND filter. The implications of these results for best clinical practice are discussed.

This provides the basis for a new treatment of amblyopia, one that is purely binocular and aimed at reducing suppression as a first step.

Amblyopia is a cortically based visual disorder caused by disruption of vision during a critical early developmental period. It is often thought to be a largely intractable problem in adult patients because of a lack of neuronal plasticity after this critical period [1]; however, recent advances have suggested that plasticity is still present in the adult amblyopic visual cortex [2-6]. Here, we present data showing that repetitive transcranial magnetic stimulation (rTMS) of the visual cortex can temporarily improve contrast sensitivity in the amblyopic visual cortex. The results indicate continued plasticity of the amblyopic visual system in adulthood and open the way for a potential new therapeutic approach to the treatment of amblyopia.