Although most clinicians know patients who have suffered a concussion are likely to experience exophoria at near, often greater than 6 prism diopters (pd), the literature is unclear on the actual prevalence: studies range anywhere from zero to 58% of concussed patients—yielding an average of 14%.

To better assess esophoria in this patient population, researchers reviewed the charts of 71 patients from a neuro-focused private practice setting. All participants had a documented diagnosis of concussion and underwent a comprehensive exam with an emphasis on near vision, including a cover test and von Graefe test.

Results show 28% of study participants experienced near esophoria ranging from 1pd to 14pd, with an average of 5.2pd.

The researchers note the prevalence, while in the mid-range of previous studies, is significantly higher than the average. This may be due to several factors, they speculate. Patients with unresolved esophoria may be more prone to seek care at a specialty neuro-ophthalmic practice. Also, many may not have received a comprehensive near vision exam, were referred for vision therapy for presumed exophoria and convergence insufficiency (more commonly reported in this population) and received counter-productive therapy that exacerbated the near esophoria.

Nonetheless, “the presence of esophoria at near in the concussed individual may be more common than typically believed to be the case, especially based on the earlier studies,” the researchers concluded in their report. “Thus, the near phoria must be carefully and fully evaluated by the clinician, as its presence has important ramifications diagnostically, prognostically, and therapeutically in the concussed individual.”