Hemianopsia - Causes and Symptoms

Definition

Hemianopsia is an alteration of vision characterized by the impossibility of perceiving a half of the visual field.

The disorder can concern, in particular, the middle of the right or left visual field (lateral or vertical hemianopsia) or the upper or lower one (altitude or horizontal hemianopsia). Hemianopsia can also be heterogeneous (loss of the two outer halves of the visual field, ie bitemporal, or internal, ie binasal) or homonymous (loss of the two left or right halves of the visual field).

This symptom is often associated with pathologies of neurological origin that cause compression of the optic pathways, as in the case of pituitary adenomas, aneurysms, traumas and brain tumors. Hemianopsia can also occur in the presence of: cerebral ischemia, intracranial haemorrhages, meningitis and circulatory problems of the eye.

Hemianopsia is caused by a lesion or compression at any level of the visual pathways. In fact, these events can compromise the normal transmission of bioelectric signals from the retina to the visual cerebral cortex.

In general, lesions can develop anteriorly, at the same level or posteriorly with respect to the optic chiasm (ie where the nerve fibers coming from the two eyes partially cross, before continuing in the optical traits and reaching the visual cortex).

The bitemporal heterogeneous hemianopsia is produced, for example, by damage in the central chiasmatic portion, therefore the perception of half of the visual space towards the outside of each eye is lost. In the very rare binasal form, instead, there is the loss of the nasal visual field for bilateral lesions interesting both the inner margins of the optic chiasm. There are also homonymous hemianopsies, in which the loss of the right or left visual field (both for the right eye and for the left eye) occurs due to the lesion, respectively, of the left or right optic tract.