Vision and TBI

One thing many may not think about is that there may be a difference in one’s vision after a Traumatic Brain Injury (TBI).

Those in the military were studied to determine the mechanisms of TBI and the visual consequences that ensued from it.

The article studied two different types of mechanisms one could receive brain injury from including blast related traumatic brain injuries (BR) and non-blast related TBIs (NBR)¹. The difference being in a BR the TBI is caused by a blast wave itself or by direct head trauma caused by the events surrounding the blast and an NBR is caused by direct head trauma¹.

The eyes are controlled by cranial nerves in the brain, CN II, CN III, CN IV, CN VI. These nerves can be damaged or destroyed in the event of a TBI due to the mechanism of the coup-contrecoup. In a coup-contrecoup the brain is literally pushed against one part of the skull and then goes quickly in the other direction to be smashed against the other side of the skull. This motion is what breaks axons in the brain and causes dysfunction in different areas of the brain as well. If any of these cranial nerves is affected with this coup- contrecoup motion then dire consequences may incur. As there are multiple cranial nerves that innervate the eye if anyone of these are injured or damaged the eye motions and movements can be affected.

In the military study they found that more than 65% of NRB and BR TBI patients reported vision problems¹. The following complaints were listed with saccadic dysfunction (abnormal latency to initiate eye movements, abnormal speed of eye movements (generally slow), or abnormal accuracy of eye movements (hypometria or hypermetria)⁴, the next was light sensitivity, accommodative (the eye changes focus from distant to near images)³, problems with convergence (the eyes have a strong tendency to drift outward when reading or doing close work ) issues^5,1. Reading complaints were reported as well as strabismus (one eye looks straight while the other does not they can’t align both eyes)² and visual field defects (visual field loss in the same area on both eyes⁶)¹.

Make sure if you are involved in a possible traumatic brain injury that you get checked out immediately. As a structural chiropractor we check these cranial nerves to see if any of them have been compromised. Working with your eye doctor may be necessary and frequent cranial nerve testing may be required until improvement is seen.

References:

1. Goodrich et al. Military and Veteran Populations. Optom Vis Sci 2013;90:105-112.
2. https://www.strabismus.org Opens in new window
3. https://www.aao.org/bcscsnippetdetail.aspx?id=0554ca9e-b088-4bfe-91ab-2fc77bb0ea67 Opens in new window
4. https://www.aao.org/bcscsnippetdetail.aspx?id=0b510213-bdbc-414e-8895-adb4e18d9573 Opens in new window
5. https://www.convergenceinsufficiency.org Opens in new window
6. http://www.sightscience.com/visual-field-deficits/ Opens in new window