Post Trauma Vision Syndrome/ Visual Midline Shift Syndrome
Following a neurological event such as a traumatic brain injury, cerebro-vascular accident, multiple sclerosis, cerebral palsy, etc., clinicians have noted that patients frequently report visual problems such as objects appearing to move that are known to be stationary, words running together when reading and trouble maintaining clear focus. Interesting symptoms are sometimes reported, such as attempting to walk on a floor that appears tilted and having significant difficulties with balance and spatial orientation when in crowded moving environments. These type of symptoms are not uncommon.
When these patients report these symptoms to eye care professionals, they are frequently told that their problems are not in their eyes and that their eyes appear to be healthy. What is often overlooked is dysfunction of the visual processing areas of the brain that have been damaged. These problems are not addressed in a routine eye examination.
Recent research has documented a syndrome known as Post-Traumatic Vision Syndrome (PTVS) utilizing Visual Evoked Potentials to measure electrical activity of the brain. This documentation concludes that the ambient visual process frequently becomes dysfunctional after a neurological event such as a brain trauma (TBI) or stroke (CVA).
Patients can often have visual symptoms that are related to dysfunction between one of two visual processes ambient process and focal process. These two systems are responsible for the ability to orient ourselves in space for balance and movement, as well as to focus on details such as looking at a traffic light. PTVS results when there is dysfunction between the ambient and focal process causing the person to over emphasize the details. Essentially individuals with PTVS begin to look at paragraphs of print almost as isolated letters on a page and have great difficulty organizing their reading ability. They become very frustrated, confused, anxious and just give up reading.
The use of prisms and bi-nasal occlusion can effectively demonstrate functional improvement in many cases, while also being documented on brain wave studies by increasing the amplitude of brain wave activity. (this is like turning up the volume on your radio).
Visual Midline Shift Syndrome (VMSS) also results from dysfunction of the ambient visual process. It is caused by distortions of the spatial system causing the individual to misperceive their position in relation to their spatial environment. This leads to a shift in their perceived visual midline, which frequently causes the patient to lean to one side, forward and/or backward. It frequently can occur in conjunction with individuals that have had a hemi-paresis (paralysis to one side following a TBI or CVA).
The shifting concept of visual midline actually reinforces the paralysis, by using specially designed yoked prisms that can be prescribed, the midline is shifted to a more centered position thereby enabling these patients to very often begin weight bearing on their affected side. This works very effectively in conjunction with physical and occupational therapy attempting to rehabilitate weight bearing and balance for walking. In addition, it can help with even simple activities like signing one's name or pouring a cup of coffee.
A thorough neuro-optometric evaluation should be performed within the first 48 to 72 hours in cooperation with the physical/occupational therapy evaluation. As with most medical treatments, time is of the essence when regaining walking ability and normal daily activities.
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