Introduction
Visual dysfunction is common after a concussion. A prospective study reported that 79/113 (70%) of adolescents had concussion-related vision problems.1 Accommodative and convergence insufficiency were the most common.1 Both can be easily screened for, as recommended by best practices in national and international concussion guidelines.2 3 Convergence insufficiency is screened for by measuring the near point of convergence (NPC), with a result of >6 cm considered abnormal.4 Accommodative insufficiency can be detected by measuring the amplitude of accommodation (AA), for which age-dependent norms are available; see figure 1.5 The American Academy of Pediatrics has suggested that a randomised clinical trial (RCT) is needed to assess the effectiveness of therapeutic interventions for concussion-related vision dysfunction.2 The CONCUSS RCT addresses this need by answering (1) the effectiveness of therapy, (2) dosing differences and (3) impact of treatment delay.6 The accompanying video and Figure 1 demonstrate how to measure and interpret the NPC and AA. The following are the best practices when measuring NPC and AA.
Figure 1
Screening tool and procedure for convergence insufficiency and accommodative insufficiency with instructional video.
Best practices
Eyeglasses should be worn, but the use of the reading portion of multifocal lenses/reading glasses during accommodative testing should not be permitted.
Positioning and starting point distance: For NPC, place the measuring rod at the forehead above the nose. For AA, occlude one eye and place the rod above the opposite eyebrow. The starting distance for the visual target should be placed at ~25 cm from the patient’s eyes.
Recommended target: A vertical line of 20/30 letters (4-point font) should be used in children and young adults, moving the target ~2 cm/s. For individuals aged 35 and above, use a solid vertical line for NPC.
For NPC, distinguish ‘blur’ from ‘double vision’: Inform the patient that the endpoint is double, not blurred, vision. Note the point where one eye starts to diverge (outward rotation) or shift side to side.
For AA, test each eye separately: AA should be measured for each eye separately, recording when blur is sustained.
Effort: For both the NPC and AA, stress the importance of ‘trying’ to keep the letters single for NPC and clear for AA. When the endpoint occurs, stop and ask the patient to try to regain single vision or clarity, respectively. Continue until sustained double vision/blur occurs and single vision/clarity cannot be recovered.
Assess symptoms: Symptoms can include headache, diplopia or eyestrain during the test, providing insight into the patient’s ability to perform near tasks.
If abnormalities in NPC or AA are detected, consider referral to an eyecare professional experienced in the assessment and management of concussion-related vision problems. More information on these assessments can be found at this instructional video https://research.njit.edu/vision/.
Data availability statement
The data will be uploaded to NIH for CDE https://cde.nlm.nih.gov/home and the NIH FITBIR (Federal Interagency Traumatic Brain Injury Research Informatics System) (https://fitbir.nih.gov/). All non-personally identifiable data supporting this study’s findings will be made available to the corresponding authors upon reasonable request.
Ethics statements
Patient consent for publication
Ethics approval
This study was approved by the Human Research Protection Office and the Institutional Review Boards at each participating institution.
