Concussion: Understanding Vision Problems Post-Injury

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December 10, 2019

By Mackenzie Simmons, ATC

Approximately 3.8 million concussions occur in the United States each year; however, this number is a low estimate due to the number of unreported concussions. Over the past few decades, concussions have been on the forefront of medical research, but it remains a complex injury to evaluate. Athletic Trainers (ATs) are usually the first health care professional to evaluate a concussion and need to do a thorough job to ensure proper care is being provided to the injured athlete. Concussions generally have symptoms that affect a patient in four main categories- physical, cognitive, emotional and sleep.

  • Physical – symptoms may include sensitivity to light and/or noise, fatigue, nausea or vomiting, dizziness, balance problems and blurred or double vision
  • Cognitive – Problems may include difficulty thinking clearly, feeling mentally slowed down, difficulty remembering and/or difficulty concentrating
  • Emotional – Symptoms may include irritability, sadness, increased emotional behavior, nervousness or anxiety
  • Sleep – Following a concussion, a person may start sleeping more or less than usual or have difficulty falling asleep

While all the signs and symptoms of a concussion can cause difficulties with recovery, this article will focus on some vision problems that can occur post-injury, including convergence excess, convergence insufficiency, accommodative insufficiency and ocular motor dysfunction.

Convergence Excess

Convergence excess is defined as an anomaly that causes the eyes to over-converge at near sights and cause the eyes to turn inwards. This causes the target to appear closer than their actual location. This disorder is typically seen in prolonged reading, where a patient must focus on small words that are centered in a small area. Some of the symptoms of this condition are like those of a concussion, so it may be hard to diagnose at first. A patient may complain of headache, eye strain or blurred vision. Other signs and symptoms include fatigue, dizziness or pain in or around the eyes.

Testing for Convergence Excess

The easiest way to test for convergence excess is through a routine eye exam with an ophthalmologist and also by determining the AC/A (accommodative convergence/accommodation) ratio. Two different methods can be used to calculate the AC/A ratio–the gradient method and the heterophoria method. Both of these tests can be completed in an ophthalmologist's office. In a patient with convergence excess, the AC/A ratio will be high and the esophoria (defined as the inward deviation of the eyes) at distance will be lesser than the esophoria at near.

Convergence Insufficiency

Convergence insufficiency is an anomaly that causes the eye to under-converge at near. The signs and symptoms with this condition are similar to convergence excess. Double vision, eye strain, blurred vision, fatigue, headache, dizziness and pain around the eye are common signs and symptoms between the two conditions. The main separation between the two is if a patient is under-converging or over-converging at near.

Testing for Convergence Insufficiency

Having a patient complete a convergence insufficiency symptom survey is a very easy and accurate way to diagnose convergence insufficiency. In this survey, patients are asked 14 questions about their experience while reading or doing close work, such as experiencing headaches, eye pain, trouble remembering and double vision. These symptoms are ranked on a scale from zero to four, and then totaled up at the end. A score of 16 or higher is a positive sign in children, and a score of 21 or higher is a positive sign in adults. Another way to test for convergence insufficiency is to hold a small target in front of the patient and move the target closer to the patient until they have double vision. A distance greater than 10 centimeters would be a positive sign for convergence insufficiency.

Accommodative Insufficiency

Accommodative insufficiency is defined as being unable to focus or maintain focus at near. Signs and symptoms of this condition include eye strain, blurred vision, fatigue and headaches. Additionally, a patient may experience eye pain, dizziness and sensitivity to light. This may sometimes be misdiagnosed as ADHD/ADD or a learning disability due to possible difficulty reading and lack of concentration.

Test for Accommodative Insufficiency

To test for accommodative insufficiency, one of the most commonly known testing mechanisms is the Donder’s push-up method. To conduct this test, the patient will be seated or standing, and the examiner will hold a piece of paper with small letters printed on it (or can be a small line in the Snellen eye chart). The examiner will then slowly move the letters closer to the eye until they become blurry, and then will measure the distance in millimeters. The measurement will then be converted to diopters (unit of refractive power that is equal to focal length of a given lens). One eye should be tested at a time.

Ocular Motor Dysfunction

Ocular motor dysfunction occurs when a patient is unable to perform accurate and/or effective ocular pursuits, fixations and saccades. Saccades are eye movements that are able to quickly re-fixate from one object to another. On the other hand, pursuits are smooth eye movements that are engaged when tracking a moving object. Fixations occur when a patient is trying to maintain their visual gaze on a single location for a significant period of time. The signs and symptoms of these conditions include poor attention span, reduced efficiency and productivity, poor academic performance, difficulty tracking or following objects, or loss of place on a page when reading.

Testing for Ocular Motor Dysfunction

Saccades – Ask a patient to look quickly between two pencils as quick as possible. Another way to test this is to stick out one hand and ask the patient to quickly look between the examiner’s nose and hand. It may also be important to figure out if a patient is having difficulty with horizontal saccades or vertical saccades.

  • Horizontal saccades – The examiner will hold two fingers out, about three feet away from the patient. The hands will be separated three feet apart (1.5 feet to each side). The patient needs to move eyes quickly from one fingertip to the other and should be repeated at least two times. Complaints of headache, dizziness and nausea could indicate a positive test.
  • Vertical saccades – The examiner will hold two fingers out, about three feet away from the patient. The hands will be separated three feet apart (1.5 feet above, 1.5 feet below). The patient needs to move eyes quickly from one fingertip to the other and should be repeated at least two times. Headache, dizziness and nausea could indicate a positive test.

Pursuits – The examiner holds a finger about three feet away from the patient. After telling the patient to keep focus on the finger, the examiner slowly moves finger 1.5 feet to the right and 1.5 feet to the left. This test can be repeated several times. Positive reports of headache, dizziness and nausea could indicate a positive test.

Fixation – The examiner holds an object in front of the patient and asks patient to focus on the object. The examiner will move the object around to see if the patient can keep a fixated on the object when the object is in motion.

Incorporating some of the vision testing listed above will help ATs to complete a thorough concussion evaluation. If a patient is having a prolonged recovery from a concussion, it may be wise to screen the patient for convergence excess, convergence insufficiency, accommodative insufficiency and ocular motor dysfunction. A referral to an ophthalmologist and a sports medicine physician should also be made to ensure quality and well-rounded care to the concussed athlete. Any of these conditions can cause schoolwork to become difficult, due to increased screen time and difficulty with reading small print. An AT doing a complete, concise concussion evaluation can help properly diagnose an athlete, thus allowing the team of health care professionals to give proper care to ensure a safe and efficient return to sport and return to school.


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