Story by: David Steen Martin Reviewed by Michael Angelo C. Huang, M.D. on January 24, 2024
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Just under half of children with brain tumors have symptoms that affect their vision.
Brain tumors either from direct compression of the visual pathway by the tumor or from elevated pressure from increased fluid (hydrocephalus) in the brain. Most children with brain tumors have obstructive hydrocephalus at diagnosis, according to Michael Angelo Huang, M.D., pediatric neuro-oncologist with Norton Children’s Cancer Institute, affiliated with the UofL School of Medicine. This is of utmost importance given that the visual system in children is still developing.
The process of seeing involves sending visual information that is registered in the back of your eyes (retina) to the brain via the optic pathway. Visual information moves through several locations in the brain before reaching the occipital lobe, where it is processed.
Swelling in the brain from a child’s tumor can cause pressure issues on the vision pathways in the brain, a condition called papilledema. Additionally, brain tumors in children also can distort or damage parts of the brain involved in the movement and focusing of the eyes and areas in the brain responsible for relaying and processing visual information in the brain.
Damage to either of these can lead to permanent vision loss or other vision issues such as strabismus, which is a misalignment of the eyes, or nystagmus, where the eyes can move uncontrollably.
Surgery and radiation therapy and less commonly chemotherapy used to treat brain tumors also can damage vision. They can cause vision loss or issues such as blurry vision or lack of color or peripheral vision. Some of these changes can be permanent.
Glasses often can fix issues with the part of vision involved in focusing what you see onto the back of your eyes. Damage to the parts of the brain involved in processing what the eyes see cannot be fixed with glasses.
The two tumors of childhood that most commonly affect vision are optic pathway gliomas and craniopharyngiomas.
An optic glioma is a slow-growing tumor in or around the optic nerve/pathways. As the tumor gets larger, it presses on the optic nerve and pathways, causing vision to get worse. Because of the location of the tumor, surgery is impossible. Treatment for an optic glioma is typically chemotherapy. There are also newer targeted cancer drugs that are not chemotherapy approved for cases that are resistant to chemotherapy.
Younger children and children with less severe vision loss when they are diagnosed with an optic glioma tend to preserve their vision better. Fewer than 5% of children with optic gliomas will go blind, but some children lose their peripheral vision because of the tumor.
Craniopharyngiomas are rare, benign brain tumors. The first symptom of a craniopharyngioma usually is unexplained vision loss. Treatment for a craniopharyngioma is surgical removal of the tumor and, sometimes, radiation therapy.
Most children with a craniopharyngioma only retain the vision they had at the time of surgery and do not recover lost vision. The reason for this is the atrophy — or withering — of the optic nerve that is already present at the time the tumor is diagnosed.
Brain tumors in children also can cause late effects related to vision. Late effects are long-term side effects from cancer treatment that continue after the treatment has ended. For example, radiation therapy can cause cataracts or damage the visual pathways in such a way that the effects are sometimes not seen for months or years.
The risk of developing late effects often depends on the specific treatments and dosages used and the child’s age during treatment.
With optic gliomas, risk factors for long-term deterioration of vision are diagnosis at a young age, size and location of the tumor, although these affect fewer than 10% of children with this type of brain tumor.
Vision issues, including blindness, are a late effect for craniopharyngiomas.