The Cortical Vision Screening Test (CORVIST) is designed to detect visual impairments in individuals with normal (corrected) or near-normal vision. It allows vision specialists without any detailed knowledge of neuropsychology to probe the higher visual areas of the brain and is designed for use with patients with visual symptoms that cannot be explained by a routine ophthalmological, optometric or neurological examination.
Used in conjunction with the VOSP|, the CORVIST provides a comprehensive assessment of visuoperceptual ability.
Nature of the tests
Each of the ten tests focuses on a different aspect of early visual processing by cortical centres. Each is prefaced by a description of its aim, the instructions to the subject, and an indication of its significance. They are simple to administer and make minimal demands on the testee.
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Symbol acuity - To simplify testing acuity in patients who have difficulty in scanning visual arrays such as a standard acuity chart.
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Shape discrimination - To detect impairment of shape discrimination in individuals who have normal acuity.
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Size discrimination - Extending and complimenting the Shape Discrimination Test. Clients, despite having normal acuity, may have difficulty completing this size discrimination test.
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Shape detection - To provide further indication of shape discrimination using more complex stimuli requiring interaction across a larger area of the visual field.
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Hue discrimination - To identify individuals with an acquired impairment of hue discrimination.
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Scattered dot counting - To detect difficulties in either the localization of a single point in space or of spatial scanning
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Fragmented numbers - To detect an impairment of perceptual identification.
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Word reading - To assess reading skills.
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Crowding - To identify individuals who show excessive impairment of acuity when symbols are closely spaced.
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Face perception - The purpose is to detect impairment in the perception of faces. Individuals with normal acuity and normal discrimination may nevertheless be impaired on more complex stimuli such as faces.
Citations
The CORVIST has been cited in the following papers:
Hickman et al. (2005) "Seeing is believing." British Journal of Ophthalmology. 89, 641-642
Charles R. F. & Hillis A. (2005) "Posterior cortical atrophy: Clinical presentation and cognitive deficits compared to Alzheimer's disease." Behavioural Neurology, 16(1), 15-23
Moss et al. (2005) "Anteromedial Temporal cortex supports fine-grain differentiation among objects." Cerebral Cortex, 15(5), 66-627