Abstract
Purpose: :
The duration of near-based study and complexity of visual interactions places increasing demands on accommodation and convergence in school children as they move into secondary school. We hypothesized that students without significant refractive error or with myopia would be less bothered by these near demands than hyperopic students who require greater active accommodation and convergence to compensate for their refractive error at near, and hence are more likely to be symptomatic.
Methods: :
A brief history was elicited from 353 students in grades 6 to 9 at a Melbourne-based middle school prior to non-cycloplegic refraction using a Shin Nippon NVision-K5000 autorefractor and completing a Borsting et al’s[1] Convergence Insufficiency Symptom Survey (CISS) in class.
Results: :
Mean age was 13.2±0.1 years and mean spherical equivalent refraction +0.05±0.74D. The prevalence of myopia (≥-0.50D SphEq) and hyperopia (≥+0.75D) were both approximately 15%. The mean symptom survey score for students without amblyopia or strabismus was ~16 (range 0-56) and showed a significant effect for refractive group, F(4, 333) = 3.46, p = .009 (h2=0.04). Post-hoc tests showed that the mean symptom survey scores were significantly higher for students with hyperopia over +2.00D (27.7±4.4) than for those with milder hyperopia (18.3±1.9), emmetropia (15.8±0.7), mild myopia (15.1±2.1) or myopia over -2.00D (13.6±1.4).
Conclusions: :
These findings partially support our hypothesis that students with hyperopia are more likely to be symptomatic. However, of interest is the fact that Borsting et al[1], the originators of CISS, found a mean CISS score of 8.4±6.4 for children with normal binocular vision aged 9-18 years. Hence, our findings would imply that a large proportion of refractively emmetropic and myopic children are symptomatic for near and raises questions regarding the incidence of binocular anomalies in this group, or, challenges the validity and reliability of the symptoms questionnaire [1,2].[1] Borsting EJ et al. Validity and reliability of the revised convergence insufficiency symptom survey in children aged 9 to 18 years. Optom Vis Sci 2003, 80 (12):832-8[2] Rouse M et al. Validity of the convergence insufficiency symptom survey: a confirmatory study. Optom Vis Sci 2009, 86(4):357-63.
Keywords: refraction • clinical (human) or epidemiologic studies: risk factor assessment • binocular vision/stereopsis