Anthony Lee / Getty Images
Anatomy of the Optic Chiasm
At the optic chiasm, nerve fibers from half of eachretinacross over to the opposite side of the brain. The fibers from the other half of the retina travel to the same side of the brain. Because of this junction, each half of the brain receives visual signals from the visual fields of both eyes.
Diseases of the Optic Chiasm
There are a number of disorders that can affect the optic chiasm. These include:
How Pituitary Adenoma Affects the Optic Chiasm
The most common disorder affecting the optic chiasm is a pituitary adenoma.Pituitary adenomas are benign tumors. In most cases, they have no impact at all, but in some cases, they can affect vision, sometimes causing vision loss.
As they grow in size, pituitary adenomas can put pressure on important structures in the body, such as the optic nerve. Putting pressure on the optic nerve may cause blindness, so it is crucial for eye doctors to detect pituitary tumors before they cause damage to vision.
The pituitary gland is about the size of a bean and is attached to the base of the brain behind the nasal area. it sits right under the optic chiasm. Although small, the pituitary controls the secretion of many different types of hormones. It helps maintain growth and development and regulates many different glands, organs, and hormones.
Changes in hormones can cause significant changes in our bodies. Besides vision changes such asdouble vision,drooping eyelids, and visual field loss, pituitary adenomas also may cause the following symptoms:
Pituitary Adenoma and Your Vision
Why Diseases of the Optic Chiasm May Be Hard to Detect
When a disease or lesion affects the optic nerve before it reaches the optic chiasm in the brain, the defect in the vision will show up in only one eye and can affect the entire field of that eye. People that suffer from a one-sided defect sometimes do not notice it until one eye is covered. This is because, when both eyes are open, the overlapping visual fields of each eye will mask the defect.
If the disease affects the optic tract at the chiasm, then the temporal visual fields will be affected in both eyes and anything further back in the brain behind the chiasm both eyes' visual field will also be affected but will be affected on the same side.
If the disease affects the optic tract after the chiasm, the person will have a defect in their vision in both eyes, but the defect will alter the same half of the visual field on the opposite side of the lesion.
4 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
Larsson M.The optic chiasm: a turning point in the evolution of eye/hand coordination. Front Zool. 2013;10(1):41. doi:10.1186/1742-9994-10-41
Gala F.Magnetic resonance imaging of optic nerve. Indian J Radiol Imaging. 2015;25(4):421-38. doi:10.4103/0971-3026.169462
U.S. National Library of Medicine.Pituitary tumor.
Meet Our Medical Expert Board
Share Feedback
Was this page helpful?Thanks for your feedback!What is your feedback?OtherHelpfulReport an ErrorSubmit
Was this page helpful?
Thanks for your feedback!
What is your feedback?OtherHelpfulReport an ErrorSubmit
What is your feedback?
