Medical Conditions Related to Brain Injury
Head Injury and Post-Trauma Vision Syndrome
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Traumatic brain injury is sudden and devastating to the individual and to the family. The victims may be in deep coma and/or have multiple injuries that affect motor function, speech, and cognition. The shock of the injury necessitates immediate emergency and medical intervention to ensure the survival of the individual.
Once the person recovers from the coma and has had his or her medical needs met, hard realities of physical limitations and cognitive function must be addressed. From tests performed to determine levels of function, physicians, physical therapists, occupational therapists, and other professionals will determine appropriate modes of rehabilitation. If concerns exist about possible ocular problems, an ophthalmologist will join the emergency team early in the treatment program to determine if the trauma has caused an impairment to the sight. We have observed, unfortunately, that throughout medical and rehabilitative treatment programs little regard is given to the individual's level of visual function. Even in later stages of rehabilitation, if a question is raised about a visual interference that may be a result of the traumatic brain injury, the recommended examination usually emphasizes sight and not visual function.
A rehabilitative approach to vision care and a routine vision evaluation that tests sight are different. The visual system has two components: a central or focal process and a peripheral or ambient process. Neurologically, the central process is attention oriented and is delivered primarily through the macula; it allows a person to center on detail. A routine eye evaluation would measure this central process (visual acuity). The peripheral process is ambient in function and involves spatial orientation and awareness. This process is different from the extent of scope of field and relates more to how peripheral visual information is used and matched with motor centers.
Routine eye examinations do not test this aspect of vision. Many of the nerve fibers from the peripheral areas of the retina are not delivered to higher cortical levels involving areas of imaging or seeing but are oriented in mid-brain or in the lower brain stem. They link up with motor centers for balance, movement, and coordination. It is this process that is evaluated during rehabilitative optometric testing.