Head injury patients frequently complain of double vision after an acute head concussion often as a result of a motor vehicle accident.
Double vision (or seeing two of things) can be very disturbing to an individual and make them unstable and unable to function in the real world. Imagine you are driving a car and you can’t tell which oncoming vehicle is the real one and which is just a shadow.
It’s important to define double vision. It can occur in several forms, the most common being side by side double vision where objects appear in duplicate side by side. There is also vertical double vision where one object appears on top of the other. And there is a combination of the two types.
Classic double vision occurs when the two eyes are not pointing in the same direction, so the brain gets separate images from each eye. The brain doesn’t like this state of affairs, so the person will often inadvertently close one eye resulting in no double vision. Thus, one very important question to ask an individual who is seeing two of things, is to ask them to close one eye. If the double vision goes away, that’s real double vision.
How does double vision relate to head injury? That’s more complicated but very important to ask about and is frequently ignored- people are embarrassed to admit they are seeing double, others might assume they are intoxicated.
Head trauma can cause double vision in a variety of ways. One is that facial trauma can directly break bones around the eye which can pinch the little muscles that move the eyeball. Yes, the eyeball is surrounded by tiny muscles (like the ones in your arm or hand), that move the eye in every direction, and those muscles can be damaged by a direct blow to the eye or fractures of the bones around the eye (such fractures are common and not easily detectable since those bones don’t move like the arms and legs.) A CT scan or MRI scan of the face can reveal such fractures.
The more common variety of double vision after a mild TBI can be more subtle, with no direct injury to the face. The brain keeps the eyes pointed straight ahead, and if the brain gets shaken hard enough this coordination can be lost. Adults and children often have a mild tendency for their eyes to turn out (wall eyes), eyes can also turn in (crossed eyes).
Children frequently inherit these tendencies and are treated by Pediatric ophthalmologists. But a concussion in an adult can cause a normal person to have a breakdown in fusion (keeping the eyes pointed straight). The cause can be complicated – subtle damage to the vision – motor centers of the brain, or direct damage to the tiny nerves that go directly from the brain to the eyes (cranial nerves). Such damage cannot be detected by a CT scan or MRI of the brain. But such abnormalities can be measured by an experienced ophthalmologist who makes these subtle measurements. My practice, because we evaluate many children and adults with double vision, is careful to measure these deviations.
Every patient with a TBI, even if he/she doesn’t complain of double vision goes through exact eye movement testing. We use a cover / uncover test where we cover one eye at a time while the patient looks at a letter on the eye chart. If there is even a subtle movement from side to side as you cover each eye, that can be a red flag for double vision.
Eye physicians use prisms, carefully designed triangular pieces of glass which bend light. Without going into unnecessary detail, such prisms can be used to quantify the amount of turning in units called diopters (like inches on a ruler).
Such measurements are extremely important because they provide objective evidence, quantifiable abnormalities that define a TBI patient. TBI patients are frequently ignored because headaches, impaired memory, and difficulty working can be hard to quantify. Such patients are often accused of malingering (just faking it).
Our TBI clinic treats TBI patients with respect, just as we treat all our patients with eye problems. Detecting even small amounts of prism deviation can be critical in improving these patients’ lives.
Prism can be introduced into glasses to sometimes correct double vision. Unlike many problems associated with TBI, ophthalmologists can provide effective therapy which is inexpensive. More severe cases require eye muscle surgery. We specialize in measuring patients for prism and these measurements need to be precise.
TBI patients need a thorough ocular motor evaluation. Objective evidence of damage is a critical component of head injury examination. Glasses with prisms may be a simple solution to relieve suffering.