Grant: Operating Grant - PA: INMHA (bridge funding)

The conventional view of 3D depth perception (stereopsis) is that information from the two eyes is fused to produce the percept of a single scene. In doing so the stereoscopic system also provides extremely detailed information about the relative depths of objects. This 'fine' stereopsis has been well-documented, and is assessed by existing clinical tests of visual ability. However, stereoscopic depth is also obtained when viewing images with very large depths that cannot be fused into a single scene. The existence of 'coarse' stereopsis was noticed in the past, but has only recently been studied systematically, and its role in vision is still not well understood. We hypothesize that coarse stereopsis appears early in life and helps the two eyes to move together so that fine stereopsis may develop. If this is the case, then lazy eye (amblyopia), a disorder that disrupts typical visual development, may have different effects on coarse and fine stereopsis. We know that children with amblyopia often have no fine stereopsis, even after treatment, but coarse stereopsis has not been assessed in these children. Furthermore, while much is known about the development of fine stereopsis in children without amblyopia, very little is known about the typical development of coarse stereopsis. We will use conventional clinical tests, and a customized computer game, to assess coarse and fine depth perception in children (4 to 12 yrs) and in adults with and without amblyopia. This will help us to establish the role of coarse stereopsis in vision and may also help in the treatment of amblyopia. For example, amblyopic children with coarse stereopsis may respond better to treatment than those without any stereopsis, and visual training with large depths may help restore binocular vision in these children.