The Centers for Disease Control estimates that more than 2.8 million people in the United States suffer a concussion -- or traumatic brain injury (TBI) -- every year, and vision can be affected.

The rate of childhood TBI visits to the emergency department more than doubled between 2001 and 2009, making children more likely than any other group to go to the ER with concussion symptoms.

It was once assumed that the hallmark of a concussion was a loss of consciousness. More recent evidence, however, does not support that. In fact, the majority of people diagnosed with a concussion do not experience any loss of consciousness. The most common immediate symptoms are amnesia and confusion.

There also are multiple visual symptoms that can occur with a concussion, either initially or during the recovery phase.

Visual symptoms after a concussion include:

• Blurred vision.

• Difficulty reading.

• Double vision.

• Light sensitivity.

• Headaches accompanying visual tasks.

• Loss of peripheral vision.

Most people with visual complaints after a concussion have 20/20 distance visual acuity so more specific testing of near acuity, convergence amplitudes, ocular motility, and peripheral vision must be done.

In a study done at the Minds Matter Concussion Program at the Children's Hospital of Philadelphia, patients with a concussion diagnosis underwent extensive vision testing, which assessed symptoms, visual acuity, eye alignment, near point of convergence, vergence amplitude and facility, accommodative amplitude and facility, and saccadic eye movement speed and accuracy.

A total of 72 children (mean age 14.6 years) were examined, and 49 (68%) of those were found to have one or more vision symptoms after concussion. The most common problems were convergence insufficiency (47.2%); accommodative insufficiency (33.3%); saccadic dysfunction (30.5%); and accommodative infacility (11.1%). The investigators also found that 64% of the children with convergence insufficiency also had an accommodative disorder.

Difficulties with accommodation and convergence make it very hard to read for any length of time, with blurring and fatigue and then loss of concentration occurring after a fairly short period of reading time.

For the majority of people suffering a mild to moderate TBI, most of these symptoms resolve in one to three weeks but in some they can persist much longer.

If your visual symptoms after a concussion persist past three weeks, a visit with an eye care specialist is recommended. There may be several options to help improve the symptoms with either prescription eyeglasses or prisms to assist the two eyes to focus together.