skotom

Skotom, also spelled scotoma, is a partial loss of vision or a blind spot in the visual field. The term derives from Greek skotos, meaning darkness, and is used in ophthalmology to describe areas where vision is reduced or absent, while surrounding vision may be normal.

There are several forms: absolute scotoma (no light perception in the affected area) and relative scotoma (reduced sensitivity). They can be central (affecting the center of gaze), paracentral, or peripheral; they may be stationary or transient. Some scotomas are congenital or physiologic, such as the natural blind spot where the optic nerve exits the retina.

Causes include retinal diseases (retinal detachment, macular degeneration, diabetic retinopathy); optic nerve diseases (optic neuritis, glaucoma); and brain or visual pathway lesions (stroke in the occipital cortex, tumors). They may also occur with migraines or as part of broader neurological disorders.

Diagnosis relies on visual field testing (perimetry) and patient mapping; imaging and anatomical assessment may include optical coherence tomography (OCT), MRI, or CT as indicated. Management depends on the underlying cause; some scotomas are permanent, while others improve when the primary condition is treated. In migraine, scotomas are often transient.

In clinical practice, skotomas are documented to map the affected field and help monitor progression or response to therapy. Related terms include scotoma and physiological blind spot.