When mild pure alexia may not be reducible to hemianopic alexia

ABSTRACT

Individuals with pure alexia often have visual field defects such as right homonymous hemianopia. Relatively few attempts have been made to develop criteria to differentiate pure alexia from hemianopic alexia. In this Commentary we provide concrete suggestions to distinguish the two disorders. We also report on additional assessments with two previously reported cases for whom the diagnosis of pure alexia was called into question and an alternative proposal was offered that the reading deficits were instead due to hemianopia. We show that the results of clinical and neuropsychological tests do not support the account that the reading impairment was caused by the visual field defect. In particular, for both cases, the right homonymous hemianopia was not complete, and a split-field reading task demonstrated an inability also to read words presented in the intact left visual field. In conclusion, pure alexics may indeed show fairly modest word-length effects; however, the presence of right homonymous hemianopia and a non-extreme gradient of reading speed alone are not sufficient grounds to put in doubt the diagnosis. We propose that a fuller clinical and neuropsychological examination taking into account the possible confounding effects of the visual field defects will help to distinguish pure alexia from hemianopic alexia.

KEYWORDS:

• Pure alexia
• right homonymous hemianopia
• word-length effect
• split-field reading task

Acknowledgments

We would like to thank Francesca Bertuzzi for her help with the perimetric data and two anonymous reviewers for useful advice on an earlier version of the manuscript.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Cristina Rosazza http://orcid.org/0000-0002-7799-415X