Vergence, accommodation, and visual tracking in children and adolescents evaluated in a multidisciplinary concussion clinic

Abstract

Many patients with concussion experience visual symptoms following injury that lead to a diagnosis of convergence insufficiency, accommodative insufficiency, or saccadic dysfunction. However, these diagnostic categories are based on aggregates of clinical tests developed from a non-concussed population and therefore may not accurately describe visual deficits in the concussed population. Thus, we sought to understand individual metrics of visual dysfunction in chronically symptomatic post-concussion patients. This retrospective cross-sectional study included patients examined at the multidisciplinary concussion clinic (MDCC) at Boston Children's Hospital over four years. Patients aged 5-21 years who had a complete assessment of eye alignment, vergence, accommodation, and visual tracking, and had visual acuity better than or equal to 20/30 in each eye were included. Patients with history of amblyopia, strabismus, or ocular pathology were excluded. Chart review yielded 116 patients who met inclusion criteria (median age 15 years, 64% female). The majority of patients (52%) experienced a single concussion and most were sports-related (50%). Clinical data show vergence, accommodation, or visual tracking deficits in 95% of patients. A receded near point of convergence (NPC, 70/116) and reduced accommodative amplitude (63/116) were the most common deficits. Both NPC and accommodative amplitude were significantly correlated with one another (r = -0.5) and with measures of visual tracking (r = -0.34). Patients with chronic post-concussion symptoms show deficits in individual metrics of vergence, accommodation and visual tracking. The high incidence of these deficits, specifically NPC and accommodative amplitude, highlights the need for a detailed sensorimotor evaluation to guide personalized treatment following concussion.

Keywords: Accommodation; Binocular vision; Concussion; Vergence; Visual tracking.

Figure 1. Incidence of abnormal findings

Incidence of abnormal findings depicted as a percentage of the 116 patients for each clinical measure (n=107 for DEM). Each finding was categorized as normal or abnormal based on criteria described in Table 1. NPC - near point of convergence, PFV - positive fusional vergence; NFV - negative fusional vergence; BI - difficulty with base in prism; BO - difficulty with base-out prism; Both - difficulty with both base-in and base-out prism; Amp - Amplitude of accommodation; MAF (−), MAF (+), MAF (+&-) - monocular accommodative facility and difficulty with minus lens, plus lens, or both, respectively; Lag of Acc- Lag (inadequate) of accommodation; Lead of Acc - lead (excess) of accommodation; DEM - Developmental Eye Movement Test

Figure 2. Relationships among ocular alignment and vergence measures

A, B Box plots showing the relationship between ocular alignment (phoria) with near point of convergence (NPC) and positive fusional vergence. P-values are listed above the graphs on brackets. C, D. Scatter plots between NPC and positive fusional vergence and between NPC and vergence facility. Regression lines are fit using total least squares (i.e. orthogonal) regression. Eso – esophoria; ortho – orthophoria; exo – exophoria; cm – centimeters; ^△ – prism diopters; cpm – cycle per minute.

Figure 3. Relationship between accommodative amplitude and vergence measures

A. Correlation between accommodative amplitude and near point of convergence (NPC). B. Correlation between accommodative amplitude and positive fusional vergence (PFV). Regression lines are fit using total least squares (i.e. orthogonal) regression. P-values are listed above the graph. D – diopters; ^△ – prism diopters.

Figure 4. Correlations of accommodative amplitude and near point of convergence (NPC) with Developmental Eye Movement (DEM) Test.

The left (A, C) and right (B, D) panels depict vertical and horizontal DEM performance, respectively. R values displayed are the Pearson correlation coefficient. P-values are listed above the graphs. Regression lines are fit using total least squares (i.e. orthogonal) regression. cm – centimeters; D – diopters.