Brain Injury
Approximately 70 percent of all sensory input fibers to the brain begin in the eye. This is more than twice the neural input of all the other senses combined. For perspective, the auditory nerve contains 30,000 neurons compared to the 1,000,000 neurons in the optic nerve.
The traditional approach to vision examination and treatment has relied on a limited concept of the visual system. In reality, the visual system is represented in every major lobe of the brain, as well as the midbrain and brainstem. Therefore, almost any neurological compromise, whether acquired (e.g. traumatic brain injury or stroke), congenital (e.g. Down syndrome or cerebral palsy), or degenerative (e.g. Parkinson’s disease or multiple sclerosis), will impact the visual system in some way.
Visual skills impacted, or visual symptoms may include:
Visual Field Loss
Visual Field Loss—this can include:
- Monocular vision loss—loss of vision in only one eye
- Hemianopia—loss of the right or left side of vision in both eyes
- Sector vision loss—loss of some part of the right or left side of vision in both eyes
- Concentric loss—constriction of the visual field in all directions
- Altitudinal loss—loss of the top or bottom part of the vision in both eyes
- Total loss of visual field
Visual Field Loss
There are typically several aspects to rehabilitation of visual field loss.- Education about the vision loss.
- Rehabilitation therapy, learning how and when to scan—this can often lead to improvement in the visual field loss itself, i.e., expansion of sighted areas. Rehabilitation therapy also includes reading strategies, visualization techniques, some orientation and mobility training and perceptual speed training so that when one scans into the blind area, they can perceive quickly what is there and move fixation back in front of them.
- “Field expansion” prisms. There are two basic types of prism.
- The Gottlieb style prism, which is set into the blind field and must be scanned into. It has been associated with recovery of visual field in some patients.
- The Peli style prism is set above and/or below the line of sight and moves images from the blind field into the sighted visual field, above or below the line of sight. This allows for an “early warning system” for objects moving into the blind visual field, where they are perceived in the patient’s intact visual periphery above or below the line of sight. The patient does not move their eyes into the prism and so this does not require attention to the blind field, making it a helpful prism for patients with visual-spatial neglect.
In addition, depending on the nature of the visual field loss, and the cognitive status of the patient, orientation and mobility training by a certified Orientation and Mobility specialist may be necessary or desirable.
A Gottlieb style prism fitting system set for a left hemianopia. Note that for someone blind on their left side, the prism is out of sight until they move their eyes to the left.
Examples of a Peli Style prism for various visual field defects. (Graphic from Chadwick Optical)
Visual Spatial Neglect
Visual Spatial Neglect—the brain areas for eyesight are intact, but the person is unable to attend to, and therefore cannot see or acknowledge, the existence of objects or their own body parts on one side of their vision. The severity of neglect in a person may vary depending on how crowded the visual environment is, or whether objects are self (e.g. arms, legs, or one side of the face), within arms reach, or beyond arms reach.
Visual Spatial Neglect
Visual spatial neglect is treated in much the same way as homonymous hemianopia (visual field loss). There must be much more emphasis on the education, as patients with visual spatial neglect will chronically forget about their condition; the hallmark of this condition is a lack of awareness of the defect. Additional scanning and therapeutic exercises, as well as Peli prism application are generally helpful. Moderate visual spatial neglect generally requires more therapy, but tends to be more remediable than moderate visual field loss.
Patient with right visual spatial neglect doing “doorjamb fixations” to practice scanning right and leftward with his eyes, rather than his head.
Eye Movement, Focusing, or Eye Coordination Defects
Eye Movement, Focusing, or Eye Coordination Defects—Includes
- Difficulty with eyesight focusing problems
- Problems with visual fixation and/or accurate eye movements
- Loss of eye movement into one or more directions of gaze for one or both eyes
- Double or confusing vision—this may be constant or intermittent
Feelings of Disorientation and Imbalance
Feelings of Disorientation and Imbalance are common following brain injury.
- Loss of balance—may be vestibular (due to inner ear or ear/brain problems), especially when accompanied by the experience of the room spinning
- General feelings of disorientation or imbalance can also be because the patient no longer visually perceives the floor as flat, or because there is a mismatch between the perceived straight ahead and the physical straight ahead due to Abnormal Egocentric Localization (AKA Visual Midline Shift Syndrome)
- The two eyes may tell the brain that the floor is at different heights in different directions of gaze
- These distortions are seldom obvious to the patient, as the brain tries to “normalize” our world for us
- Specialized testing is required to discover the actual cause
Feelings of Disorientation and Imbalance
Feelings of imbalance or disorientation following brain injury are frequently due Abnormal Egocentric Localization. This can lead to veering or leaning to one side during walking or driving. It is common following stroke or traumatic brain injury. Other causes of disorientation or feelings of imbalance include Post Trauma Vision Syndrome (see below), or small vertical misalignments of the eyes, which change the appearance of the height of the floor, steps, or curb as one shifts gaze from left to right. Specialized “yoked” prism can be ground into the patient’s glasses, or used for vision rehabilitation therapy to normalize the patient’s perception of straight ahead. If a small vertical misalignment of the eyes is present, then vision therapy to help the patient to learn to point the two eyes accurately, or partial patches on their glasses lenses may be required.
Vision rehabilitation therapy patient using yoked rehabilitation lenses and peripheral vision stimulation to remediate Abnormal Egocentric Localization.
Patient using the Space Fixator to improve spatial localization and reduce visual confusion.
Post Trauma Vision Syndrome
Post Trauma Vision Syndrome has been called the most common visual sequel to traumatic brain injury. It can lead to:
- Abnormal Egocentric Localization
- Severe difficulty or discomfort in visually busy surroundings or with repeating patterns in carpet or wallpaper
- Staring or inattentive behavior
- Difficulty focusing and eye teaming, especially for near tasks
- Difficulty with reading
- Difficulty with visual memory
- Photophobia—light sensitivity
- Visual memory loss
Reading difficulty can be caused by any of the above visual defects.
Headache can be caused by any of the above visual defects.
Dry eyes are common following brain injury; there are multiple solutions available depending on the severity of the problem.
Form Perception Deficits
Form Perception Deficits—difficulty understanding what one is seeing. Form perception deficits are treated with vision rehabilitation therapy with a combination of manipulatives; paper, cognitive, and computer therapies.
A comprehensive Post Stroke/Brain Injury Work Up is the first step to properly diagnosing any visual/cognitive problems.
Dr. Penelope S. Suter and staff are proud to serve patients in Bakersfield as well as surrounding communities such as Arvin, Delano, Frazier Park, Lake Isabella, Lamont, Lancaster, Palmdale, Porterville, Shafter, Taft, Tehachapi, Visalia, Wasco, and many more. Our services include, but are not limited to, diagnosis and treatment of vision issues that result in reading, spelling, and other learning deficits, as well as vision dysfunction that results from autism spectrum disorder, brain injury, or other neurological compromise. Treatment may include lenses, prisms, colored filters, vision therapy, and post brain injury vision rehabilitation.