The Relationship Between Binocular Vision Symptoms and near Point of Convergence and Jump Convergence Anomalies in Students of Zahedan University of Medical Sciences

With attention to the high prevalence of binocular vision anomalies, specially, convergence anomalies among university students which cause symptoms such as eye-strain, binocular vision symptoms, headache and problems in near daily activity, this study aims to assess the relationship between binocular vision symptoms and near point of convergence and jump convergence anomalies in students of Zahedan university of medical sciences. In this cross-sectional study, 181 students were selected randomly, and divided into symptomatic and asymptomatic groups. At first, refractive errors of individuals were determined by retinoscopy and corrected, if necessary. The convergence status was evaluated by near point of convergence and jump convergence. NPC, as the nearest point that subjects report diplopia, was determined using small isolated letter of approximately 20/30 (6/9) size from snellen reduced chart and jump convergence by two targets in different distances 15 and 50 cm along the median plane. The data were analyzed through SPSS software version15 using descriptive and analytical statistics of t-test, χ2 and ROC curve. From 181 students, 56 students (30.9%) were symptomatic and 125 (69.1%) asymptomatic. The means of near point of convergence in all subjects, symptomatic and asymptomatic ones, were 10.95, 15.20 and 9.05 cm, respectively. The normal patterns of jump convergence in all persons, persons with and without symptoms, were 72.4, 37.5 and 88 percent, respectively. In this study, a significant difference was found between NPC and symptoms (p<0.001) and symptoms and jump convergence (p=0.01). Abnormal near points of convergence and jump convergence can produce binocular vision symptoms hence, the use of these two tests for evaluation of convergence status is necessary and if there is any functional abnormality, appropriate treatment options are selected. Often this problem can be easily managed by orthoptics.