Approximately 70% 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 — 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 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.
- 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 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.
- However, 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).
- It may also result because the two eyes 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.
- 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—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.
The optometrists and staff at Dr. Penelope S. Suter’s office 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, general optometry, vision therapy, diagnosis and treatment of eye disease and conditions and the treatment of vision issues that result from brain injury or other neurological compromise.