Certified Ophthalmic Technician (COT) Practice Test 2025 - Free COT Practice Questions and Study Guide

Homonymous hemianopia is characterized by the loss of vision in half of the visual field, typically affecting the same side of both eyes. This condition arises usually due to lesions in the optic pathways, particularly in the optic tract or the visual cortex in one hemisphere of the brain. When a person has homonymous hemianopia, their vision is intact on one side while there is a noticeable deficit on the opposite side, which can severely impact daily functions and spatial awareness.

In contrast, a quadrantic defect refers to loss of vision in a specific quadrant of the visual field rather than half, a scotoma indicates a small area of diminished or absent vision within an otherwise normal visual field, and ametropia describes refractive errors where the eye does not focus light correctly on the retina. None of these conditions encapsulate the concept of half-field loss as effectively as homonymous hemianopia does. Understanding these terms helps to distinguish how various visual field defects present and their implications for treatment and management.