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Prisms throw light on developmental disorders.

Brookes RL, Nicolson RI, Fawcett AJ. (2007)Neuropsychologia, 45, 1921-1930.

Prisms have been used by developmental optometrists to influence a wide variety of visual functions. This paper, the results of research by experimental psychologists published in a neuropsychology journal, supports a scientific model for the powerful influence of prisms.

Prism adaptation is a fundamental form of motor learning, and has been selectively linked to the cerebellum. The role of the cerebellum in motor development is well-known, but less well-known is the recent evidence linking deficits in cerebellar function with dyslexia.

Direct evidence for the role of the cerebellum in dyslexia includes behavioral evidence of posture and balance deficits; eye movement deficits; impaired eye blink conditioning, and motor sequence learning deficits. Studies showing these connections are cited in this paper.

The research paradigm used in the present study involved motor performance first with prisms in place, and then a re-adaptation rate when prisms were removed. The subjects with developmental coordination disorder (DCD) and dyslexia had reduced ability to adapt, and the experiment controlled for attention and distractibility factors.

This study concludes that the slower prism adaptation data are consistent with the cerebellar deficit hypothesis of dyslexia. The cerebellar deficit hypothesis supports the use of motor and prism activities that have been a mainstay of optometric vision therapy programs.