Abstract
Background: Childhood visual impairment is a global public health problem, especially in developing countries. Its most common causes are avoidable by early diagnosis and treatment.
Aims: To assess prevalence of refractive error (RE) and visual impairment (VI) among school-aged children in Hargeisa, Somaliland.
Methods: This was a cross-sectional study of 1204 students (aged 6–15 years) in 8 randomly selected primary schools in Hargeisa from November 2017 to January 2018. We used the modified Refractive Error Study in Children to determine prevalence of RE and VI, including the following investigations: distance visual acuity, assessed by Snellen Tumbling E-chart; refraction, assessed by retinoscope binocular vision assessment; and examination of anterior and posterior segments.
Results: Prevalence of uncorrected, presenting and best-corrected VI of 6/12 or worse was 13.6%, 7.6% and 0.75%, respectively. Only 16 of 91 (17.6%) children were using spectacles and the rest were unaware of the problem. RE was the cause of VI in 76.8% of participants, amblyopia in 22.0%, trachoma in 2.4%, and corneal opacity and cataract in 0.6%. Anterior segment abnormalities were found in 8.3%, mainly vernal keratoconjunctivitis, while posterior abnormalities were observed in 0.7%. Prevalence of myopia was 9.1%, hypermetropia 2.7% and astigmatism 3.9%. Prevalence of VI because of RE was associated with increasing age, but there was no significant association with school grade or sex.
Conclusion: Prevalence of VI among school-aged children in Hargeisa was high, and the leading cause was uncorrected RE. There are barriers to care and it is critical that they are overcome.
Keywords: refractive error, childhood visual impairment, myopia, hypermetropia, vernal keratoconjunctivitis
Citation: Abdi Ahmed ZD; Alrasheed SH; Alghamdi W. Prevalence of refractive error and visual impairment among school-age children of Hargesia, Somaliland East Mediterr Health J. 2020;26(x):xxx-xxx http://doi.org/10.26719/emhj.20.077
Received: 18/3/2019, Accepted: 19/11/2019
Copyright © World Health Organization (WHO) 2020. Open Access. Some rights reserved. This work is available under the CC BY-NC-SA 3.0 IGO license (https://creativecommons.org/licenses/by-nc-sa/3.0/igo)
Introduction
Globally, it is estimated that there are 36 million people who are blind, 216.6 million have moderate to severe visual impairment (VI) and 188.5 million have mild VI. The leading cause of VI is uncorrected refractive error (RE) (1,2). Furthermore, 90% of people with VI live in developing countries. Almost 19 million children aged < 15 years have VI globally. In developing countries, 7–31% of childhood blindness is avoidable, 10–58% is treatable, and 3–28% is preventable (3). RE is an eye condition in which light from a distant object is not focused on the retina; it might be focused in front of or behind the retina. There are 3 types of RE: myopia, hypermetropia and astigmatism. The exact cause of ametropia remains unknown with common risk factors being hereditary, nutritional and environmental (4). Population-based studies on VI and RE in children have been conducted on populations with different racial backgrounds and environments in Africa. These studies have shown that the prevalence of VI among children was 2.15% in South Africa (5), 5.5% in Khartoum, Sudan (6), 4.4% in South Darfur, Sudan (7), and 9.5% in Ethiopia (8). World Health Organization (WHO) defines VI in children as presenting with visual acuity (VA) less than 6/12 in the better eye. However, uncorrected VA (UVA) is defined as VA less than 6/12 in one or both eyes (7). VI among children in developing countries is a priority of eye health programmes, including Vision 2020: the Right to Sight Initiative (9). Globally, the principal cause of VI is uncorrected REs (43%) and cataracts (33%) (1). Special attention should be given to children, because VI restricts their education and general performance, personality development, future quality of life and career opportunities (10). The Refractive Error Study in Children (RESC) protocol was developed by WHO in collaboration with, and under financial support from the National Eye Institute, National Institutes of Health and the United States of America to assess the prevalence of VI and RE worldwide, as well as to assess the effect of childhood VI due to uncorrected RE (11,12).
Republic of Somaliland has a population of 4.5 million, with estimated urban poverty of 29%, which is similar to 26% in Ethiopia. Only about half of children aged 6–13 years go to primary school in Somaliland, in stark contrast to 87% in neighbouring Ethiopia (13, 14). No studies have assessed VI and RE among school-aged children in Hargeisa, Somaliland. The aims of this study were to assess the common causes of VI, types of RE, and differences in prevalence according to sex, age and school grade.
