The brain lesions could lead to impairments of the comprehension and production of written language. This acquired inability is named alexia. It is a significant problem for neurologists and ophthalmologists. Our study presents a classification of the alexias, whose pathology was describe first by Dejerine (1891; 1892). There are two varieties of alexias: central alexias and peripheral alexias (especially agnozic alexia and attentional alexia). In agnozic alexia, the patient cannot read, but can write, understand and speak. It results from a type of cerebral disconnection in which the angular gyrus of the dominant hemisphere is disconnected from its bilateral visual input. The most commonly reported pathology is occlusion of the dominant (left) posterior cerebral artery, which leads to infarction of both the left occipital lobe (causing partial or complete right homonymous hemianpsia) and the splenium of the corpus callosum.