Learn about various causes of increased eye pressure that result from eye trauma and how this medical problem is managed.
Glaucoma is defined as a type of optic neuropathy (damage to the optic nerve) that has a many causes. Severe trauma to the eye can lead to direct optic nerve damage. Although such damage is referred to as traumatic optic neuropathy, it is important to understand that a damaged optic nerve is more vulnerable to sustain further glaucoma-related damage, especially when the eye pressure is elevated. Therefore, it is critical to report the history of eye trauma when seen by eye care professionals and to follow their recommendations for follow up visits. Commonly, traumatic glaucoma is caused by elevated intraocular pressure (IOP), which, as with other types of glaucoma, can lead to optic nerve damage. The following discussion will focus on the cause of elevated IOP induced by trauma. Ocular trauma could be penetrating or non-penetrating.
Penetrating Eye Trauma
The penetrating trauma is often an emergency and requires surgical repair as the eye contents could be damaged and foreign objects needs to be removed if present. The direct penetrating injury could occur in the eye fluid drainage system, called the trabecular meshwork, and subsequently lead to the build-up of pressure. In addition, inflammation and scar formation in the drainage system may ensue after surgical repair, which eventually leads to its impaired function and ultimately elevated IOP and optic nerve damage.
Non-penetrating Eye Trauma
Non-penetrating trauma is seemingly less detrimental, but IOP elevation could be equally or even more severe. For example, chemical burn could lead to the shrinkage of the tissue in the drainage system and loss of function, resulting in elevated IOP. Bleeding inside the eye caused by blunt trauma (called hyphema when the blood is present in the anterior chamber of the eye) could cause the blockage of eye fluid and elevated IOP.
However, there are more microscopic circulating red blood cells that could easily overwhelm the capacity of the eye’s drainage system. In fact, many incidences of elevated IOP are caused by microhyphema (a small amount of bleeding in the anterior chamber of the eye) which could not be easily appreciated without a careful eye exam. This may give patients a false sense of security, especially patients with sickle cell disease, as those misshaped red blood cells (sickle cells) have more difficulty to exit the eye through the drainage system.
In addition, blunt trauma to the eye could directly injure the eye’s drainage angle even without evidence of hyphema. The “angle” referred to here is the angle between the iris, which makes up the colored part of your eye, and the cornea, which is the clear-window front part of your eye.
The hallmark of such an injury is angle recession. However, this could be easily overlooked as the angle is not visible unless a prism lens (called goniolens) is used during the exam. Without the goniolens, the initial eye exam could appear entirely normal, including normal eye pressure. When the residual normal part of the angle eventually loses its ability to compensate the injured part, the IOP becomes elevated. It is important to know that this process is slowly progressive. It is not uncommon for elevated IOP to be discovered decades later. Just like most types of glaucoma, patients remain entirely asymptomatic until advanced stages of the disease.
Glaucoma is one of the most common causes of irreversible blindness, but it is also a treatable disease. It is straightforward to manage the elevated IOP caused by bleeding with eye drops or surgical removal of the blood. Patients with hyphema (even microhyphema) should be advised to protect the injured eye with an eye shield when sleeping and limit their physical activity to prevent recurrent bleeding. Patients should also alert their physicians of their sickle cell disease status if it is known. When in doubt, a sickle cell test can be easily performed. It is imperative to be an advocate for yourself to remind your eye doctor of the history of eye injury so that appropriate plans for follow up and treatment can be implemented.