chiasm
Optic Nerve Crossing
Plain-language definition
The X-shaped junction where the optic nerves partially cross so each side of the brain receives visual information from both eyes. Lesions here cause characteristic visual field loss.
Where this term comes up
“It occurs when the optic chiasm, where the optic nerves cross, is compressed, typically by a pituitary tumor or other lesion at the base of the brain.”
Finding · Bitemporal Hemianopia
“When large enough, they can compress the optic chiasm (where the optic nerves cross), causing a characteristic pattern of vision loss affecting peripheral vision in both eyes.”
Condition · Pituitary Tumor
“These tumors can grow large enough to compress the optic chiasm, causing visual field defects.”
Medication · Dopamine Agonists (Cabergoline, Bromocriptine)
- Category
- Anatomy
- Also written as
- chiasmal
Anatomy terms name the eye, orbit, optic nerve, retina, or visual pathway structures that may appear in an exam note or imaging report.
Related glossary terms
- MRI
Magnetic Resonance Imaging
- ischemia
Reduced Blood Supply
- hemianopia
Loss of Half of Vision
- OCT
Optical Coherence Tomography
- bitemporal
Outer Vision in Both Eyes
- afferent
Carrying Signals to the Brain
A note on medical context
A glossary definition can explain a word, but it cannot tell you whether a symptom or test result is serious. If this term came from an article, use the full article and your clinician's guidance for context.