Why permanent vision loss may occur after head trauma

Head injuries may result in permanent vision loss, and a new study from the University of Texas Medical Branch in Galveston has revealed why. Head trauma can cause damage to the optic nerve that relays information between the eyes and the brain, and when damage occurs, tears and swelling in the area can result in the death of optic nerve cells. This damage is referred to as traumatic optic neuropathy (TON) and results in permanent vision loss. Researchers explored what mechanisms specifically cause nerve cell death, with the hopes that better understanding of the cause may lead to treatment and prevention strategies.

The study was led by associate professor Wenbo Zhang, who used mice to help determine the cause of the damage. The team found that inflammation of the affected area plays a part in causing irreversible vision loss. When an injury occurs, the body reacts by sending white blood cells to the affected area to aid in the repair of damaged tissue. While this is a normal response crucial to wound healing, the influx of white blood cells may also cause excessive inflammation and make existing damage worse. Uncontrolled inflammation can cause cell death, rupture and clog blood vessels, and produce toxic free radicals.

With this understanding, researchers either removed a specific protein receptor on white blood cells from the mice’s genetic code or gave them a drug that blocked these receptors.
Zhang commented on the results, stating, “Our data clearly shows that one of the protein receptors on white blood cells called CXCR3 brings white blood cells to the optic nerve in response to production of its binding partner CXCL10 by damaged nerve tissue. When we deleted CXCR3 or gave mice a drug that blocks the receptors following optic nerve damage, we observed fewer white blood cells on the scene by real-time noninvasive imaging, nerve damage was deceased and nerve cell function was preserved compared with mice that did not receive any intervention following injury.”

Nerve injury has also been linked to stroke, diabetic retinopathy, and glaucoma, meaning the potential application of these results could reach further than vision loss associated with head injury. Researchers hope that with further testing, intervention and prevention techniques may be developed to stop the development of irreversible vision loss due to damage of the optic nerve.

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