Prevalence of Convergence Insufficiency in a Population of University Students

Purpose:
Convergence insufficiency (CI) is one of the most important binocular vision disorders. Because there is no previous report on CI prevalence in an Iranian population, the purpose of this study is to estimate the frequency of CI in a population of 18 to 30 years old university students in the rehabilitation faculty of Iran University of Medical Sciences.
Methods:
160 students aged 18 to 30 years (mean± SD = 21.7 ± 2.8 age) that had no glasses or had worn glasses or contact lenses≥ 1 month with corrected or uncorrected visual acuity of 20/30 or better in both eyes and uncorrected refractive error less than or equal to -0.5 D to +1.00 D, or ≤ 1.00 D astigmatism in either eye or ≤ 1.00 D anisometropia and no strabismus, were enrolled to evaluate the presence of CI. Individuals with following clinical signs were considered as a CI patient: near point of convergence (NPC) of ≥ 10 cm, exophoria at near ≥4∆ more than far measurements, insufficient fusional convergence amplitude according to sheard criterion, normal amplitude of accommodation according to Hofstetter formula (minimum age appropriate amplitude of accommodation= 15- 0.25× age in years ) . The prevalence of CI was calculated based on the abovementioned data.
Results:
Regardless of accommodative condition, 10% of the study population showed CI disorder. 25% of this population showed lower amplitudes of accommodation compared to the normal accommodative values. Indeed, 7.5 % were CI and 2.5 % were pseudo CI.
Conclusion:
The results of the present study demonstrated a high frequency of CI in population of university students. Because of the symptoms of CI during near work activities such as reading and using computer, screening and applying appropriate treatments seem to be essential.