visual field defect, one or more spots or defects in the vision that remain constant in position, unlike a floater. This fixed defect is usually caused by damage to the retina or visual pathways, such as by retinal detachments, chorioretinitis, traumatic injury, macular degeneration, glaucoma, or a vascular occlusion of the eye or the brain. Sudden loss of a noticeable part of the visual field warrants ophthalmological examination. An Amsler grid detects defects only in the central 30°—not the entire visual field.
