Determining Near Point of Convergence: An Exploration of One Component of the Vestibular/Ocular Motor Screen Compared to Varied Target Sizes

Abstract

ObjectiveSport-related concussions are considered a public health issue due to the number of athletes who sustain concussions.BackgroundThe Vestibular Ocular Motor Screening (VOMS) Assessment appears to be useful in evaluating concussion. Investigators have reported that abnormal near point of convergence (NPC), a component of the VOMS, is associated with prolonged concussion recovery. The purpose of this study was to compare four commonly used approaches to estimating NPC.Design/MethodsFour methods of measuring NPC were evaluated (tip of a pen, 12-point font, 14-point font, and the Bernell Vergel™ 9-point font). A generalized estimating equations approach was used to compare NPC measurements with the four methods, employing one practice trial, followed by three test trials. A sequential Bonferroni adjustment was used for pairwise comparisons. NPC estimate was modestly correlated with age of the subject, so age was included as a covariate. Significance was set at p = 0.05, a priori.ResultsSeventy-five healthy adults (16 males, 59 females; mean age, 21 ± 6.12 years, range, 18-58 years) were tested. The mean (standard error) for NPC was 7.13 ± 0.36 (95% CI, 6.45, 7.88). The smaller targets (Bernell Vergell™ and pen) yielded significantly larger estimates of NPC than both the 12- and 14-point font targets, p < 0.001). The Bernell Vergell™ and pen NPC did not differ (p = 0.134), and the 12- and 14-point font NPC’s did not differ (p = 0.794).ConclusionsEvaluation of NPC in the clinical environment uses non-standardized items of convenience that vary in size. The results of this study suggest that size is an important consideration when measuring NPC. Multiple disciplines are investigating NPC because of its relationship with concussion. Using evidence-based assessment tools such as the VOMS requires a systematic approach. Precision is required in clinical assessment, so it is suggested that clinicians use one standard approach to estimate NPC.