Visual Pathway Overview
The visual pathway runs anteriorly from the eyes all the way to the very back of the cerebral cortex in the occipital lobes. Therefore, it isn’t surprising that many of our PLGA children will have vision issues either from the tumor directly, increased pressure from hydrocephalus or from treatment complication.
To our knowledge, there have been no studies on long term neurologic and neurosensory deficits for adult survivors of PLGA brain tumors, though there has been a study conducted by Dr. Roger Packer relative to all childhood brain tumors.
Potential Visual Problems
Type of Testing/Doctor
Many of our PLGA children will be seen by an ophthalmologist or a neuro-ophthalmologist (a doctor specializing in diseases affecting vision that originate from the nervous system). Testing may include checking eye movement, looking at the back of the eye with an ophthalmoscope, visual acuity and in some instances visual field testing. Vision Loss and Education Students with vision loss may need accommodations academically. Such accommodations may include preferred seating in the front of the room, enlarged materials, magnifiers, a reader or scribe, a tape recorder, extended test time, material in braille, etc.
Other Helpful Resources
The American Foundation for the Blind offers many resources which will help inform patients/families about specially trained rehabilitation teachers, orientation and mobility specialists, low-vision specialists, and vision rehabilitation therapists, you can learn the essential skills for living with vision loss.
Recording for the Blind & Dyslexic (RFB&D), a national nonprofit volunteer organization, offers educational materials for students with disabilities such as visual impairment or dyslexia that make reading standard print difficult or impossible.
- Enucleation: This is loss of the eye. This is rare and generally only occurs when there is an optic nerve glioma that actually affects the nerve at the orbit/eyeball.
- Field Cuts: The visual field is the entire area that is seen with the eye. A field cut is when part of that area which one would be expected to see cannot. The field cut depends on the location of injury along the visual pathway. Different pattern field cuts occur with different lesions.
- Pediatric Homonymous Hemianopia: This a disabling condition caused by numerous lesions affecting the retrochiasmal visual pathways. Little is known about homonymous hemianopia in childhood, however, a study was conducted by Emory University in 2006 which concludes that trauma and tumors are the most common cause of homonymous hemianopia in childhood.
- Vision Loss: Loss of visual acuity is most common with optic pathway gliomas where the tumor compromises the nerve tract. Increased intracranial pressure (such as with untreated hydrocephalus) can cause optic nerve atrophy>resulting in vision loss.
- Eye Misalignment (acquired strabismus): Either from tumor or from injury to the cranial nerves going to the eye, some children with brain tumors will develop eyes that are misaligned. Children who have misaligned vision may complain of double vision or have a head tilt (which may help compensate for an eye muscle that is not working well correcting double vision). This may correct on its own with treatment or as the surgical trauma resolves. During this time patching one eye is common as young children will learn to suppress one image (potentially becoming functionally blind in one eye over time). Patching one eye will resolve the double vision. Some children will benefit from surgery to align the eyes.
- Nystagmus: This is an involuntary movement of the eyes and can occur as a tumor symptom or after surgery depending on the location of the tumor.
- Inability to Blink: Some children will sustain damage, usually post-surgical, to the 7th cranial nerve which controls the ability to close the eye tightly. These children are at risk for eye problems from drying as well as inability to protect the eye with a blink reflex. Patching and artificial tears may be necessary. If the nerve does not recover a variety of options are available. Although NOT Bell’s Palsy, it is similar, thus a lot of good information can be acquired through websites related to Bell’s Palsy.
- Ocular Management in Facial Paralysis: Paresis of the orbicularis oculi muscle results in diminished blink, incomplete eyelid closure (lagophthalmos), impairment of the nasolacrimal pumping system, and occasional eyelid malposition (paralytic ectropion). The ophthalmic management of paralytic lagophthalmos is directed at maintaining a normal corneal epithelium which provides comfort and preserves visual acuity. The Pediatric Brain Tumor Facial Paralysis List Serve is a place to meet other patients and parents of patients who struggle with these issues.