A New Approach to Restoring Visual Acuity and Stereopsis in Adults with Amblyopia

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Amblyopia is a deficit that arises from abnormal visual experience early in life, most commonly when the two eyes are not aligned (strabismus) or have unequal refractive error (anisometropia). It has long been thought to develop into a permanent deficit unless properly treated early in life; however, recent studies call this into question [1-8]. Adult amblyopes can recover some visual functions. Thus, amblyopia provides a useful model for understanding how to unlock adult neural plasticity. Our main aim is to develop new interventions for restoring visual acuity and stereopsis in adults with amblyopia by embedding visual training in active and rewarding visuomotor tasks that require stereopsis. Our work during the current grant period indicates that playing action-packed video games enhances several aspects of vision in amblyopic adults. Training either monocularly or under dichoptic conditions results in improved visual acuity and reduced suppression in adults with amblyopia. However, it is now clear that both perceptual learning (PL) and videogame play (VGP), whether monocular or dichoptic, result in only a modest improvement in visual acuity (by one to two lines), and only limited improvement in stereopsis [1,3-8]. Much recent work has focused on the role of binocular suppression, as the key to recovering visual functions in amblyopia. Specifically, it has been suggested that treatment should be dichoptic – and aimed at eliminating suppression - rather than monocular [5-8]. However, our pilot studies call this approach into question, and suggest a more direct approach to improving both visual acuity and stereopsis: training under 3D conditions. By forcing the two eyes to coordinate and integrate their signal in the service of a common output, stereopsis provides a unique common teaching signal to the two eyes that may be central to overcoming amblyopia. Our emphasis on stereopsis is novel, but it is based on: (1) our pilot data, showing that in adults with amblyopia, training stereopsis directly resulted not only in improved stereopsis, but also in improved visual acuity and contrast sensitivity, as well as reduced inter-ocular suppression and (2) the loss of stereopsis has demonstrable negative effects on everyday activities that can significantly impact individual's quality of life as well as limit their career choices and activities. The most noticeable qualitative deficit associated with amblyopia is impaired or complete loss of stereoscopic depth perception. Thus, the Aims of this proposal are: 1) To develop an integrated, immersive 3D videogame training program for adults with amblyopia; 2) Develop a battery of outcome measures to evaluate the effectiveness, mechanisms and “real world” impact of training 3) Evaluate the effectiveness of direct training of stereopsis on vision recovery in adult amblyopes.