After experiencing a concussion injury, lingering functional deficits can manifest, particularly in cases of post-concussion syndrome (PCS). Symptoms such as headaches, dizziness, difficulty concentrating, and blurred vision can all indicate the presence of PCS.
PCS often involves various functional disturbances in the nervous system, one of the most common being a disruption to the visual and vestibular systems. In this article, we will explore the functional disturbance known as convergence insufficiency, discuss methods for testing it, and introduce a corresponding treatment approach to provide symptom relief and enhance functional improvements for your patients.
Visual convergence is the coordinated brain-controlled inward movement of both eyes, allowing us to see a single clear image of near objects or close-up targets. It is a crucial mechanism in our oculomotor system, enabling our eyes to maintain alignment and follow a target accurately as it approaches. In most individuals, normal convergence is typically measured to be less than 10 centimeters (ideally, <5cm). (1) *PMID: 34963569
This means that our oculomotor system can effectively track a target up to 5-10 centimeters away without experiencing blurriness or double vision. However, convergence insufficiency occurs when an individual experiences blurred or double vision while attempting to track a target that is located farther than 10 centimeters from their field of vision.
After a concussion injury, various symptoms can manifest. While it is crucial to rule out any red flags indicating serious injury, it is common for symptoms to persist for months or even years in cases of Post-Concussion Syndrome.
Convergence insufficiency can be a contributing factor among the frequently observed symptoms, including blurry vision, double vision, difficulty with eye movements, increased symptoms during close activities, difficulty focusing, and motion sickness.
Some of the described symptoms can be related to other functional disturbances, such as blood flow dysregulation or cervical spine involvement. A proper eye exam from a trained healthcare provider can detect an eye coordination problem and can help pair the proper vision therapy needed for complete symptom relief.
An “on the field” example: Athletes with convergence insufficiency involved in throwing sports frequently have trouble catching balls due to difficulty accurately tracking the objects (i.e., ball) thrown toward them.
Research indicates that convergence insufficiency can persist in patients for months following their initial concussion injury. As a clinician, it is essential to consider diverse treatment approaches such as manual therapy, rehabilitation, and vision therapy.
Assessing for convergence insufficiency and evaluating its impact on symptom provocation is crucial when working with post-concussion patients.
In suspected concussion patients, a standard method to test for convergence insufficiency is a part of the Vestibular-Oculomotor Screen (VOMS). This assessment aims to evaluate various mechanisms that may contribute to residual symptoms following a concussion injury.
During the VOMS assessment, it is crucial to recognize that symptom provocation is a fundamental part of the test and indicates relevant functional impairment.
When conducting the complete VOMS assessment, particularly the convergence test, clinicians should inquire about pre- and post-test patient-reported symptom provocation. Comparing the scores before and after the test allows observation of whether the patient genuinely experiences symptoms associated with a specific mechanism. These pre- and post-test convergence symptoms should be compared to their measured NPC (i.e., is it <5-10 cm?).
Once a patient has been diagnosed with convergence insufficiency, it is essential to determine an effective treatment approach to rehabilitate this functional disturbance.
While specific treatments like visual therapy can be beneficial, adopting a comprehensive approach yields better results. Studies have demonstrated that solely focusing on vestibular training leads to success in only 25-50% of patients.
A thorough treatment protocol will include combining exercises, manual therapy, and proper patient education.
One of the first steps in treating convergence insufficiency is pairing it with the appropriate visual therapy. A commonly used rehabilitation tool is called the pencil push-up exercise. Pencil push-ups are an excellent starting point because they are easy to perform and require minimal resources and space.
To perform the “Pencil Push-Up,” hold a pencil out at arm’s length and focus on the small letters on the side of a pencil. Gradually move the pencil closer to the bridge of your nose while maintaining focus on the letters, stopping just before experiencing double vision. Hold this position for 10 seconds, then move the pencil back to arm’s length.
Repeat this exercise for 10 repetitions, 3-4 times daily, for 5-6 days. You can gradually increase the frequency and duration of the exercise, and if needed, you can reduce the hold time to 5 seconds instead of 10.
It is essential to educate patients that experiencing mild symptom provocation during the exercises is necessary to stimulate neural plasticity and facilitate positive change.
In the VOMS assessment, clinicians assess the symptom provocation of headache, dizziness, nausea, and fogginess. A study by Elbin et al. in 2018 (3) confirmed that if a patient experiences symptom provocation equal to or greater than a 2-point increase from baseline on the VOMS, that specific functional mechanism should be considered significant.
Further investigation and treatment should be pursued as it indicates a higher likelihood of the mechanism causing symptom provocation during daily activities. Patients who consistently practice eye exercises despite symptom provocation have been shown to have greater visual skills and convergence ability outcomes.
In the case of convergence insufficiency, cervical spine dysfunction has been identified as a contributing factor. Treating the cervical spine can help address convergence insufficiency by targeting the cervical-ocular reflexes (COR).
Since our eyes and neck muscles are intricately connected, disruptions in one mechanism can cause a mismatch of information within the central nervous system, resulting in symptom provocation. Hence, combining different treatment approaches is vital for complete symptom relief and recovery.
Convergence insufficiency symptoms can sometimes be mistaken for other functional impairments that occur after a traumatic brain injury. Performing a detailed exam that focuses on the detection of different key functional dysfunctions following a mild traumatic brain injury will assist clinicians in the proper detection of convergence insufficiency.
Performing a VOMS assessment with an eye exam can help guide clinicians on the proper visual therapy interventions.
Patients with convergence insufficiency often report experiencing increased symptoms when engaging in close-up activities or trying to focus on nearby objects.
If initial rehabilitation efforts prove unsuccessful, referring the patient to a neuro-optometrist may be necessary. This referral aims to explore additional interventions, such as prism glasses or further evaluation of depth perception, binocular vision, and eye movements.
Passive treatment is often the initial approach taken by most clinicians practicing manual therapy. However, it is crucial to incorporate rehabilitation exercises targeting both the eye muscles and cervical spine for more significant improvements.
Active treatment should form the foundation of care for individuals with convergence insufficiency. If a convergence insufficiency is detected, the use of pencil push-ups can be a great, accessible part of the treatment plan.
Booth M, Powell J, McKeon P, Jennifer M, McKeon M. Vestibular Rehabilitation Therapy for Management of Concussion: A Critically Appraised Topic. International Journal of Athletic Therapy and Training. 2019;24(1):100-107
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