Scotoma: Types, Causes, Diagnosis, and Management of Visual Field Defects

A scotoma is a localized area of reduced or absent vision within the visual field, surrounded by areas of normal vision. Understanding the type and location of a scotoma provides critical clues to its underlying cause.

Types of Scotomas

• Central scotoma: Involves the fovea; seen in macular disease and optic neuritis.
• Paracentral scotoma: Near fixation; characteristic of early glaucoma and macular edema.
• Peripheral scotoma: Arc-shaped (Bjerrum scotoma) or nasal step; classic for glaucoma.
• Scintillating scotoma: Fortification spectra (zigzag lines) typical of migraine aura.
• Physiological blind spot: Corresponds to the optic disc; normal in all individuals.

Common Etiologies

• Retinal disorders: Age-related macular degeneration, diabetic retinopathy, retinal detachment.
• Optic nerve pathology: Glaucoma, optic neuritis, ischemic optic neuropathy.
• Neurological conditions: Occipital stroke, tumors causing homonymous hemianopia.
• Functional disorders: Conversion disorder.

Diagnostic Workup

• Confrontation visual field testing (bedside screening).
• Automated perimetry (Humphrey 24-2, 10-2 protocols).
• Optical coherence tomography (OCT) of retinal nerve fiber layer and ganglion cell complex.
• Fundus examination and neuroimaging (MRI) when neurological etiology is suspected.

Management Principles

Treatment targets the underlying cause. For permanent scotomas, low-vision rehabilitation and assistive devices are beneficial. Scintillating scotomas from migraine may respond to prophylactic migraine therapy.