If you can understand the lower figure on this page, then you have learned the major pathway that visual information takes on its way from the eye to the primary visual cortex.
The figure is really not too difficult to understand Imagine that the colored bar half red, half blue is in front of your eyes. The red part of the bar will project to the nasal part of your left retina and the temporal lateral part of your right retina. The blue part of the bar will project to the nasal part of your right retina and the temportal lateral part of your left retina. Right and left visual information cross to opposite sides of the brain.
This crossover occurs in the optic chiasm. After the optic chiasm, information about the right visual field blue is on the left side of the brain, and information about the left visual field red is on the right side.
There, the optic nerve from each eye divides, and half of the nerve fibers from each side cross to the other side. Because of this arrangement, the right side of the brain receives information from the left visual field of both eyes, and the left side of the brain receives information from the right visual field of both eyes. Damage to an eye or the visual pathway causes different types of vision loss depending on where the damage occurs.
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The Manual was first published in as a service to the community. Learn more about our commitment to Global Medical Knowledge. This site complies with the HONcode standard for trustworthy health information: verify here. Common Health Topics. Optic Nerve Disorders. The most common disorder affecting the optic chiasm is a pituitary adenoma. 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.
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. 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 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.
Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Larsson M. Front Zool. Gala F. Magnetic resonance imaging of optic nerve. Indian J Radiol Imaging. Progressive loss of vision caused by asymptomatic pituitary macroadenoma: role of OCT. Int Med Case Rep J.
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