Ways of seeing and perceiving in cases of visual impairment

Our perceptual experience is dependent, in part, on the limits of our visual function. Those whose vision is impaired must therefore experience a corresponding shift in their perceptual experience of the world. The limits of visual function can be measured using psychophysical techniques that relate the characteristics of a precisely defined stimulus to an individual’s subjective response to that stimulus. Using such standardised techniques it is possible to characterise visual disorders in terms of their psychophysical signatures but little work has been done on how these measurable deficits in visual function alter everyday perceptual experience.

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Sound is a crucial modality for many who are visually-impaired.

Working with patients from Moorfields Eye Hospital who have been diagnosed with a range of inherited retinal disorders, my research investigates how perception, and so our conscious model of the world, is affected by specific deficiencies in different, identifiable components of the visual system.

Colin was born completely blind and has taught himself to use echo-location so that he can move around more independently.

Things come into focus and get larger as I move towards them. But if I go somewhere really open, like the beach, for example, there’s nothing there so I find it very disorientating.

George, in contrast, has some vision but can only see in good light. Now in his seventies, he was born with a condition known as Congenital Stationary Night Blindness that results in him being unable to see at all in dim light or in darkness.

Reflections are a great friend to a person who’s got my eye problem. On a dry evening I could walk slap-bang into a parked car, but when it rains you’ve got all this glistening, the kerb is lit up by reflections. It won’t throw out enough light to light my way but it would throw out enough light for me to be able to navigate better.

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There are non-visual ways of navigating even the most subtle features of a landscape.

Each subject’s account of the ways in which they see and make sense of the world are being gathered over a period of twelve months using interview-based, documentary filmmaking techniques. To date, seven patients have consented to be involved in the study, presenting with a range of retinal disorders that includes deficits of both central and peripheral vision as well as acquired and congenital vision loss. Extant research involving the subjective accounts of those with poor vision has generally focused on quality of life issues following eye surgery, and on the effect of visual impairment in ageing populations, but these accounts tend to be gathered using standardised questionnaires. The novelty of my research is in its emphasis on establishing longer-term, trusting relationships with each subject, in order to achieve a more in-depth, revealing, and rigorous account of how measurable deficits in visual function affect an individual’s daily life and influence their conscious model of the world.

Dr Jocelyn Cammack
Institute of Ophthalmology, University College London

Jocelyn was awarded an Early Career Fellowship grant in 2011. This study is also supported by the National Institute for Health Research Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and University College London Institute of Ophthalmology, and by Moorfields Eye Hospital Special Trustees.