The Vergence Endurance Test (VET), a quantitative and objective eye movement assessment, was utilized to differentiate control from concussed subjects. Nine symptomatic concussed (2 male; 30.8 -11 years) and 9 asymptomatic control (6 male; 25.1 -1.4 years) subjects participated in the VET. Symmetrical disparity vergence step targets were presented with and without visual distractors. A masked data analyst measured vergence latency, peak velocity, response amplitude, settling time, and the percentage of trials which contained blinks. A Binocular Precision Index (BPI) and a Binocular Accuracy Index (BAI) were calculated to quantify the changes that occur in the vergence parameters over the duration of the VET. Convergence and divergence peak velocity, divergence response amplitude, the percentage of trials that contained blinks during the transient portion of the response, and the BAI were significantly ( p < 0.05) different between the concussed and the control subjects. For these parameters, the BAI and divergence response amplitude yielded the greatest accuracy, 78%, in their ability to discriminate between the groups. The VET objectively measures the change in vergence performance over time and shows promise as a method to diagnose a concussion. Future studies will determine whether the VET can be used to assess the extent of natural recovery and the effectiveness of therapeutic interventions.

SIGNIFICANCE: This is the first report recording an accommodative disorder after concussion characterized by periodic moderately sized myopic refractive error fluctuations without measurable other features of spasm of the near reflex. PURPOSE:Objectively document a class of accommodative dysfunction that may be related to concussion. CASE REPORTS: Case 1 involved two sports-related concussions 2 months apart with symptoms of headache and variable blur. Refractive stability was measured 28 months after injury with a binocular open-field refractometer documenting fluctuations from −0.25 to −1.75 D occurring 10 times during 4.2 seconds of recording with no evident miosis or convergent strabismus. The symptoms resolved with 1% atropine  3 weeks. Case 2 involved a concussive blast injury (improvised explosive device) 7 years prior with symptoms of headache behind the eyes and occasional variable blur and reduced tolerance of electronic displays and other visually intensive tasks. Refractive fluctuations from +0.50 to −2.00 D occurred seven times over 44 seconds of recording with no appreciable miosis or change of interpalpebral fissure. The signs and symptoms were unresponsive to seven occupational therapy sessions involving task modifications and accommodative vision therapy activities. CONCLUSIONS: In patients complaining of blurry vision, a careful evaluation of the stability of accommodation is indicated.

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