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Year : 2016  |  Volume : 8  |  Issue : 1  |  Page : 10-13

Refractive errors status among children examined at optical center in Khartoum state

1 Associate Professor of Optometry, Al-Neelain University, Khartoum, Sudan
2 Algazira Optical Centre, General Manager, Buraidah, Saudi Arabia
3 Assistant Professor of Optometry, Al-Neelain University, Khartoum, Sudan and Qassim University, Buraidah, Saudi Arabia

Date of Web Publication17-Jun-2016

Correspondence Address:
Atif Babiker Mohamed Ali
Faculty of Optometry, Al-Neelain University, Khartoum
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/1858-540X.184236

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Background: Uncorrected refractive errors continue to remain a public health problem in the different population groups. Among children, it has a considerable impact on learning and academic achievement, especially in under-served communities. Optical correction of refractive errors in children is indicated when the refractive errors are sufficiently large to cause amblyopia or impairing the child's ability to function normally. Objective: The study aimed to investigate the distribution pattern of refractive errors and related visual impairment due to amblyopia in children. Materials and Methods: The recorded data of 183 children examined at optical center during the period (2007-2011) were reviewed and analyzed to show refractive status. The examination included visual acuity measurements, cover test, and noncycloplegic refraction (retinoscopy and/or autorefraction). The best-corrected visual acuity was noted. Results: The age range of children was 5-15 years, of whom 72 (39.3%) were males and 111 (60.7%) females. There was no significant difference in the correction of the two eyes and no gender associations. In this study, 97 (53.0%) were myopic, 17 (9.3%) hypermetropic, 42 (22.9%) pure astigmatic, and 27 (14.8%) normal. An adequate improvement of vision after correction in each eye reached 1.0 (6/6) achieved in 123 (67.2%) children (P < 0.0001) while binocular amblyopia found in 46 (25.2%) children and monocular amblyopia found in 14 (7.6%). Cover test mainly for near showed 126 (68.9%) children with associated exophoria, 7 (3.8%) with esophoria, and other 7 (3.8%) have manifest strabismus, and only 43 (23.5%) have orthophoria. Conclusions: Significant refractive errors revealed among children aged 5-15 years. Therefore, there is a need to have eye examination in school-age children at least at the commencement of school so as to early tackle disabilities due to amblyopia in children.

Keywords: Amblyopia, refractive errors, visual acuity

How to cite this article:
Ali AB, Talha AK, Elmadina AM. Refractive errors status among children examined at optical center in Khartoum state. Sudanese J Ophthalmol 2016;8:10-3

How to cite this URL:
Ali AB, Talha AK, Elmadina AM. Refractive errors status among children examined at optical center in Khartoum state. Sudanese J Ophthalmol [serial online] 2016 [cited 2023 Sep 28];8:10-3. Available from: https://www.sjopthal.net/text.asp?2016/8/1/10/184236

  Introduction Top

An estimated 153 million people over 5 years of age are visually impaired as a result of uncorrected refractive errors, of which 8 million are blind.[1] Global estimates by the World Health Organization (WHO) on visual impairment and its causes in 2010 reported uncorrected refractive error (43%) as the major cause of visual impairment.[2]

Childhood visual impairment due to refractive errors is one of the most common problems among school-age children and is the second leading cause for treatable blindness.[3] Vision 2020: The Right to Sight, a global initiative launched by a coalition of nongovernment organizations and the WHO [4] is to eliminate avoidable visual impairment and blindness on a global scale.

Poor vision and an inability to read material on the school board due to refractive error can profoundly affect a child's participation and learning in the classroom.[5] Vision is important in development because it allows children to interact with their environment. Vision in preschool children is uniquely important because their visual system is still developing, and they are at risk of developing amblyopia from some forms of uncorrected high ametropia or anisometropia and deprivation may lead to long-term visual impairment.[6] In school-based study done in Sudan (2013), the overall prevalence of refractive error was 2.19%. Myopia was found in 10,064 (1.50%) children while 4661 (0.70%) were hypermetropic.[7] Other studies in the world found that myopia was the common type of refractive error as examples in Saudi Arabia (2013: 65.7%), Malaysia (2008: 77.5%), Nepal (2010: 59.8%), India (2009: 20.65%), Jordan (2009: 31.05%), and Qatar (2010: 25.54%) of screened errors among 6-14 years schoolchildren.[8]

Failure to compensate for a heterophoria will result in a heterotropia, but the failure of compensation does not depend on the size of the heterophoria but rather on inadequate fusional reserves. There have been differences in the reported prevalence and distribution of heterophoria at near. However, previous studies of children are in agreement that orthophoria predominates at distance fixation and the relationship between heterophoria and refractive error has often been claimed, and studies specifically investigating this link have reported no association or no direct relationship between the amount of ametropia and heterophoria.[9]

This study aimed to gather information on the refractive status during school-age and to highlight their effect on vision and binocularity.

  Materials and Methods Top

This study reviewed183 records of children aged 5-15 years who were refracted at Algazira optical center between 2007 and 2011. The children's age, sex, and type of refractive error were recorded. The refractive status was grouped into myopia, hypermetropia, and pure astigmatism. Astigmatism was considered in the minus cylinder format and was included as such when cylindrical error was ≥0.50 in any axis.

All children recorded data included the following examinations in the following sequence: Visual acuity measurement of each eye separately with a Snellen test types before and after correction (a pin-hole used when visual acuity not reaches 6/6), cover-uncover test (distant and near), assessment of near point of convergence, and noncycloplegic refraction using autorefractometer (8100, Topcon, Japan) and retinoscopy (Neitz RX, Japan).

The data obtained were analyzed using the Statistical Package of the Social Sciences software version 16 (SPSS 16) and scientific calculator. The t-test was used to compare variables and a P< 0.05 was considered clinically significant.

Definitions of variables

In the current study, myopia was defined as a spherical equivalent refractive error of at least −0.50 D in one or both eyes. Hypermetropia was defined as a spherical equivalent refractive error of at least +0.75 D or more in one or both eyes. Astigmatism was defined as cylinder power ≥0.50 (no compound spherical error) in one or both eyes. Amblyopia was defined when binocular or monocular optimal visual acuity is subnormal (<6/6) even after full refractive correction.[10]

  Results Top

In this study, we found 72 (39.3%) males and 111 (60.7%) females but there is no gender correlation with type of refractive error. There was no significant difference in correction of the two eyes and an adequate improvement of vision after correction in a separate eye reached 1.0 (6/6) achieved in 123 (67.2%) children (P< 0.0001) while binocular amblyopia found in 46 (25.2%) children and monocular amblyopia found in 14 (7.6%).

  Discussion Top

Refractive errors in children are an important public health issue. Clinical evidence suggests refractive errors along with amblyopia, and strabismus is common in children.

This study will be compared with some hospital-based and community-based studies. In this study, however, the small sample size and the differences in definitions may be responsible for the high prevalence observed.

The trend of refractive errors in this study elicited myopia was the common type found [51%, [Table 1] which not differ than other studies in Saudi Arabia, Malaysia, Nepal, India, Jordan, and Qatar of screened errors among schoolchildren.[8] In the current study, we have found a high prevalence of astigmatism [21%, [Table 1] and similar results have been reported from Qatar (70%), Ghana (49.3%), Pakistan (35.5%), and Jordan (20.4%).[8] In Ethiopian study (2001), about 98% of the children with refractive errors of <6/12 were myopic indicating that myopia was a prevalent visual problem in schoolchildren.[11] In the Nigerian hospital-based study, myopia with 70 (61.4%) cases was the most common refractive error followed by astigmatism with 31 cases (27.2%). Hypermetropia with 13 (11.4%) cases was the least common.[12] On the other hand, this study is different compared to findings of Pavithra et al. (India: 2013) among schoolchildren which revealed that the prevalence of hypermetropia, myopia and astigmatism was 5.0%, 1.7% and 6.6%, respectively.[13] Some studies found that astigmatism is more dominant of other types of errors; for example, in Nepal study (2012), the most common type of refractive error among children was astigmatism (47%) followed by myopia (34%) and hypermetropia (15%).[14]
Table 1: The distribution of refractive errors in the two eyes

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According to the form of astigmatism [Table 2], the direct form (with-the-rule) is the most common in this age which represents 58% and this is in agreement with study of Mohamed Ali et al., which showed the direct form (with-the-rule) (42.5%) being more common in youth and the inverse form (against-the-rule) more in advanced life.[15]
Table 2: Distribution of astigmatism forms

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Exophoria is more dominant in this study [Table 3] which is in agreement with other studies; for example, the Australian study which showed exophoria was highly prevalent at near fixation (age 6: 58.3%, age 12: 52.2%). Orthophoria predominated at distance fixation (age 6: 85.4%, age 12: 90.9%).[9]
Table 3: Results of cover test assessment

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This study revealed that a significant improvement of vision was achieved after correction [Table 4] in each eye reached 1.0 (6/6) in 123 (67.2%) children (P < 0.0001). However, binocular amblyopia found in 46 (25.2%) children and monocular amblyopia found in 14 (7.6%). This functional visual problem appears high because most children have defective vision and come to clinic seeking visual correction. However, these results can be compared to the study done by the refractive error study in children group, and refractive error was the major cause of visual acuity of 0.5 (20/40) or worse in at least one eye in 89.5% of children in China and 56% in Nepal.[16],[17]
Table 4: Results of visual acuity before and after correction

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  Conclusion Top

This study may reflect that myopic and astigmatic trend is most probably due to the occurrence of civilizational changes such as the increase in intensive near work including reading and writing. Furthermore, the occurrence of hypermetropia in young children decreases with age. Thus, children are born with physiological hyperopia; in the course of time, the optical components in the eyeball change and this may be aggravated by intensive close work.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

WHO. Prevention of blindness and deafness. Available data on blindness, update 2006. Geneva: WHO; 2006.  Back to cited text no. 1
Pascolini D, Mariotti SP. Global estimates of visual impairment: 2010. Br J Ophthalmol 2012;96:614-8.  Back to cited text no. 2
Alam H, Siddiqui MI, Jafri SI, Khan AS, Ahmed SI, Jafar M. Prevalence of refractive error in school children of Karachi. J Pak Med Assoc 2008;58:322-5.  Back to cited text no. 3
Pizzarello L, Abiose A, Ffytche T, Duerksen R, Thulasiraj R, Taylor H, et al. Vision 2020: The Right to Sight: A global initiative to eliminate avoidable blindness. Arch Ophthalmol 2004;122:615-20.  Back to cited text no. 4
Negrel AD, Maul E, Pokharel GP, Zhao J, Ellwein LB. Refractive Error Study in Children: Sampling and measurement methods for a multi-country survey. Am J Ophthalmol 2000;129:421-6.  Back to cited text no. 5
Ibironke JO, Friedman DS, Repka MX, Katz J, Giordano L, Hawse P, et al. Child development and refractive errors in preschool children. Optom Vis Sci 2011;88:181-7.  Back to cited text no. 6
Rushood AA, Azmat S, Shariq M, Khamis A, Lakho KA, Jadoon MZ, et al. Ocular disorders among schoolchildren in Khartoum State, Sudan. East Mediterr Health J 2013;19:282-8.  Back to cited text no. 7
Al Wadaani FA, Amin TT, Ali A, Khan AR. Prevalence and pattern of refractive errors among primary school children in Al Hassa, Saudi Arabia. Glob J Health Sci 2012;5:125-34.  Back to cited text no. 8
Leone JF, Cornell E, Morgan IG, Mitchell P, Kifley A, Wang JJ, et al. Prevalence of heterophoria and associations with refractive error, heterotropia and ethnicity in Australian school children. Br J Ophthalmol 2010;94:542-6.  Back to cited text no. 9
Kleinstein RN, Jones LA, Hullett S, Kwon S, Lee RJ, Friedman NE, et al. Refractive error and ethnicity in children. Arch Ophthalmol 2003;121:1141-7.  Back to cited text no. 10
Tibebu K, Getu DA. Prevalence of refractive errors in pre-school and school children of Debark and Kola Diba towns, North-Western Ethiopia. Ethiop J Health Dev 2001;17:117-24.  Back to cited text no. 11
Ibeinmo O, Adedayo A, Megbelayin E. Refractive error pattern of children in South-South Nigeria: A tertiary hospital study. Sky J Med Med Sci 2013;1:10-4.  Back to cited text no. 12
Pavithra MB, Maheshwaran R, Rani Sujatha MA. A study on the prevalence of refractive errors among school children of 7-15 years age group in the field practice area of a medical college in Bangalore. Int J Med Sci Public Health 2013;2:641-5.  Back to cited text no. 13
Rai S, Thapa HB, Sharma MK, Dhakhwa K, Karki R. The distribution of refractive errors among children attending Lumbini Eye Institute, Nepal. Nepal J Ophthalmol 2012;4:90-5.  Back to cited text no. 14
Mohamed Ali AB, Lakho KA, AbdElbagi AE. Physical and physiological changes with presbyopia. Pak J Ophthalmol 2014;30:78-81.  Back to cited text no. 15
Jialiang Z, Xiangjun P, Ruifang S, Sergio RM, Robert DS, Leon BE. Refractive error study in children: Results from Shunyi District. China Am J Ophthalmol 2000;129:427-35.  Back to cited text no. 16
Pokharel GP, Negrel AD, Munoz SR, Ellwein LB. Refractive error study in children: Results from Mechi Zone, Nepal. Am J Ophthalmol 2000;129:436-44.  Back to cited text no. 17


  [Table 1], [Table 2], [Table 3], [Table 4]

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