Stereopsis and Amblyopia

Child playing

Amblyopia is an important condition since it is one of a leading cause of visual loss in infants and young children. It reflects the neurological damage that arises when normal visual development is disrupted. Amblyopia is a condition that provokes professionals to understand when and how brain plasticity can be used to restore visual functions. Amblyopia have a significant influence on visual motor activities and sports performance in children. Under binocular viewing conditions, the most prevalent defect associated with amblyopia is impaired stereoscopic depth perception. In this blog, we are going to focus on stereopsis, i.e., the perception of depth and three-dimensional structure through binocular vision and the possibilities for recovery of it. Stereopsis is more impacted in strabismic than in anisometropic amblyopia.

There are various approaches to treating amblyopia (patching, perceptual learning, videogames), both in anisometropic and strabismic amblyopes. However, recovery of stereoacuity may require more active treatment in strabismic than in anisometropic amblyopia. Individuals with strabismic amblyopia have a very low probability of improvement with monocular training.

Why does stereopsis matter?

Stereoscopic disparities strongly contribute to depth and shape perception when presented in conjunction with other depth cues. Studies found that there is a correlation between stereopsis acuity and driving performance. Moreover, amblyopes with poor stereopsis have visual-guided hand movement impairments identical to those generated by occluding vision in one eye in normally sighted participants, according to a number of studies. Poor stereopsis, rather than lower visual acuity, fixation instability, or impaired vergence control, is considered to be the cause of these deficiencies. In addition, poor stereoacuity in amblyopic individuals appears to hinder visual feedback control of motions, leading to much longer and less precise hand movements. Losing stereopsis has consequences that go beyond hand motions. Without stereopsis, adaptations to change in terrain (e.g. steps) are significantly less accurate, both in normally sighted monocular individuals and in persons with amblyopia and reduced stereoacuity or no stereopsis.

Key findings:
– Impaired stereopsis is very common deficit associated with amblyopia.
– Impaired stereopsis may have a substantial impact on visuomotor tasks.
-Impaired stereopsis may also limit career options for adults with amblyopia.

Sources: Levi, D. M., Knill, D. C., & Bavelier, D. (2015). Stereopsis and amblyopia: A mini-review. Vision Research, 114, 17–30.