Near vision anomalies in Black high school children in Empangeni, South Africa: A pilot study

Abstract

Background: The ability to read efficiently and comfortably is important in the intellectual development and academic performance of a child. Some children experience difficulties when reading due to symptoms related to near vision anomalies. Aim: To explore the feasibility of conducting a large study to determine the prevalence, distribution and characteristics of near vision anomalies in high school children in Empangeni, South Africa. Methods: The study was a cross sectional descriptive pilot study designed to provide preliminary data on prevalence, distribution and characteristics of near vision anomalies in a sample of high school-children in South Africa. Study participants comprised 65 Black children (30 males and 35 females), ages ranged between 13 and 19 years with a mean age and standard deviation of 17 ± 1.43 years. The visual functions evaluated and the techniques used included visual acuity (LogMAR acuity chart), refractive error (autorefractor and subjective refraction), heterophoria (von Graefe), near point of convergence (push-in-to-double), amplitude of accommodation (push-in-to-blur) accommodation facility (± 2 D flipper lenses), relative accommodation, accommodation response (monocular estimation method) and fusional vergences (step vergence with prism bars). Possible associations between symptoms and near vision anomalies were explored using a 20-point symptoms questionnaire. Results: Prevalence estimates were: Myopia 4.8%, hyperopia 1.6% and astigmatism 1.6%. For accommodative anomalies, 1.6% had accommodative insufficiency while 1.6% had accommodative infacility. For convergence anomalies, 3.2% had receded near point of convergence, 16% had low suspect convergence insufficiency, no participant had high suspect convergence insufficiency, 1.6% had definite convergence insufficiency and 3.2% had convergence excess. Female participants reported more symptoms than the males and the association between clinical measures and symptoms were not remarkable. Conclusion: Although the overall prevalence of near vision anomalies was low, convergence anomalies were found to be more prevalent than refractive and accommodative anomalies. Symptoms were not significantly associated with near vision anomalies. Overall, the pilot project reveals that it is feasible to conduct the study on a large scale with minor modifications. Identification and referrals for near vision anomalies are important steps towards diagnosis and treatment which will minimize discomfort with reading and subsequent poor performance which may be associated with such anomalies.

Vergence anomalies in a sample of high school students in South Africa

“…Using the formula 31 : where n = sample size; Zα = 1.96 = (CI: 95%) (level of significance); p = expected prevalence or proportion (in decimal point) = estimate of 17.9% prevalence of convergence anomalies from our pilot study. 7 …”

“…1 , 2 , 4 , 5 This is relevant given that a great amount of time that a child spends on academic activities both at school and home entails using the accommodative–vergence mechanism. 6 , 7 It has been reported that children with accommodative–vergence anomalies are at greater risk for reading and learning problems. 4 , 7 Etiological factors in functional vergence anomalies relate to Skeffington's 5 model of near point stress, which attributes the development of binocular dysfunctions to deficiencies in the relation between accommodative and vergence interactions.…”

“…6 , 7 It has been reported that children with accommodative–vergence anomalies are at greater risk for reading and learning problems. 4 , 7 Etiological factors in functional vergence anomalies relate to Skeffington's 5 model of near point stress, which attributes the development of binocular dysfunctions to deficiencies in the relation between accommodative and vergence interactions. 5 Such deficiencies and associated symptoms are primarily aggravated by prolonged visually demanding, near-centered tasks such as reading, writing or computer-based work.…”

“…2 , 4 Other negative consequences associated (non-causal) with VAs include reported associations between CI and attention deficit hyperactivity disorder (ADHD), anxiety, emotional and social problems. 7 …”

Stereoacuity and refractive, accommodative and vergence anomalies of South African school children, aged 13–18 years

“…5), using the standard von Graefe technique to assess heterophoria and FV would have allowed for consistency in approach. However, we used von Graefe and prism bars (as in our pilot study, 47 we confirmed that the children would have difficulties with rotary prisms to measure FVs in a school setting). However, the possible influences of this change in measurement methodology are unknown.…”