Linking binocular vision neuroscience with clinical practice

Abstract

Binocularity in the human visual system poses two interesting and extremely challenging questions. The first, and perhaps most obvious stems from the singularity of perception even though the neural images we see originate as two separate images in the right and left eyes. Mechanistically we can ask how and where do we convert two images into one? The second question is more of a “why” question. By converting lateral eyes with their inherent panoramic visual field into frontal eyes with overlapping binocular visual fields, primates have developed an extremely large blind region (the half of the world behind us). We generally accept that this sacrifice in visual field size was driven by the potential benefit of extracting information about the 3rd dimension from overlapping right and left eye visual fields. For some people, both of these core processes of binocularity fail: a single fused binocular image is not achieved (when diplopia or suppression is present), and the ability to accurately represent the 3rd dimension is lost (stereo-blindness). In addition to these failures in the core functions of the human binocular system, early imbalances in the quality of right and left eye neural images (e.g. due to anisometropia, monocular deprivation, and/or strabismus), can precipitate profound neurological changes at a cortical level which can lead to serious vision loss in one eye (amblyopia). Caring for patients with malfunctioning binocular visual systems is a core therapeutic responsibility of the eye care professions (optometry, ophthalmology and orthoptics) and significant advances in patient care and subsequent visual outcomes will be gained from a deeper understanding of how the human brain accomplishes full binocular integration.

This feature issue on binocular vision brings together original articles and reviews from leading groups of neuroscientists, psychophysicists and clinical scientists from around the world who embrace the multidisciplinary nature of this topic. Our authors have taken on the big issues facing the research community tasked with understanding how binocular vision is meant to work, how it fails, and how to better treat those with compromised binocularity. These studies address deep issues about how the human brain functions and how it fails, as well as how it can be altered by therapy.