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Year : 2018  |  Volume : 31  |  Issue : 1  |  Page : 293-298

Refraction errors in school children

1 Department of Ophthalmology, Faculty of Medicine, Menoufia University, Menoufia, Egypt
2 Department of Ophthalmology, Faculty of Medicine, Tanta University, Tanta, Egypt

Date of Web Publication14-Jun-2018

Correspondence Address:
Marian S. S. Salem
Faculty of Medicine, Tanta University, Tanta, Gharbia
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/mmj.mmj_115_17

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The aim of the study was the detection and estimation of refractive errors among school children in Tanta to allow for early correction of diagnosed children. A cross-sectional study was used.
Refractive error is one of the most common causes of visual impairment and the second leading cause of blindness following cataract.
Patients and methods
Children aging from 11 to 15 years at different public and private schools in Tanta city were included in the study. Twenty-five classes were randomly selected from 10 schools, eight public and two private, in Tanta and they were included in the study. The field work was carried out between December 2015 to March 2016. A total of 1272 students were examined at the schools: their visual acuity and autorefraction were assessed; moreover, they underwent an external eye examination. Those diagnosed with any refractive errors were referred to Tanta ophthalmology hospital for glasses prescription.
The prevalence of refraction errors among school children was 68%. The most frequent error was myopia (55.3%) followed by astigmatism (51%), and hypermetropia (11.4%). Myopia was more frequent in boys (56.5%). Hypermetropia was more frequent in girls (13.3%), and astigmatism also was more frequent in girls (54.1%). Amblyopia represented 12% of total children who had errors, and 8% of all children. Anisometropia was found in 1.8% of children with errors.
Refractive errors affected approximately more than half of the students. Myopia was the more frequent refractive problem. Most of the children were unaware of their refractive errors. The majority of the students were never examined for visual acuity. Most refractive errors can be corrected early in the life. Therefore, every child should receive eye examination by an ophthalmologist at the time of entry into school.

Keywords: Egypt, refractions errors, Gharbia, school children, Tanta

How to cite this article:
Farida FM, Hassan Farahat HG, Salem MS. Refraction errors in school children. Menoufia Med J 2018;31:293-8

How to cite this URL:
Farida FM, Hassan Farahat HG, Salem MS. Refraction errors in school children. Menoufia Med J [serial online] 2018 [cited 2022 Jan 18];31:293-8. Available from: http://www.mmj.eg.net/text.asp?2018/31/1/293/234205

  Introduction Top

Refractive errors occur when the shape of the eye prevents light from focusing directly on the retina. The length of the eyeball (longer or shorter), changes in the shape of the cornea, or aging of the lens can cause refractive errors.

The most common types of refractive errors are myopia, hyperopia, presbyopia, and astigmatism.

Myopia (nearsightedness), hyperopia (farsightedness) is a common type of refractive error where distant objects may be seen more clearly than objects that are near. However, people experience hyperopia differently. Some people may not notice any problems with their vision, especially when they are young. For people with significant hyperopia, vision can be blurry for objects at any distance, near or far. Astigmatism is a condition in which the eye does not focus light evenly onto the retina, the light-sensitive tissue at the back of the eye. This can cause images to appear blurry and stretched out. Refractive error is one of the most common causes of visual impairment and the second leading cause of blindness following cataract [1]. There are an estimated 500 million people, mostly in developing countries, including children that do not have access to eye examination and affordable correction. Many are not aware that there is a cure for their compromised vision or cannot afford the appliance they need for correction [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]. WHO and a coalition of nongovernment organizations launched a global initiative, Vision 2020: the right to sight [4]; one of its priorities is the correction of refractive errors and low vision to eliminate avoidable visual impairment and blindness on a global scale [5]. To reduce the occurrence of avoidable visual impairment and blindness caused by refractive errors, there is an urgent need for obtaining the epidemiological information on refractive errors and other eye diseases among school-age children. In China, the problem of uncorrected refractive error is particularly common, and the refractive errors have become one of the leading causes for visual impairment and blindness, especially among children [1]. Refractive errors affected approximately more than half of the students between the 7 and 15 years in Qavin, Iran [6]. Children with refractive errors are less likely to opt for correction until they are significantly visually impaired and have difficulty performing specific visual tasks. This is especially so in rural and urban poor regions where there are inadequate eye care services. Regular eye screening programs in schools will help in the early detection and correction of refractive errors. Schools with long-established tradition of engaging in vision screening have proven to be effective in detecting previously undiagnosed conditions including refractive errors [7]. Impairment due to refractive error in any population suggests that eye care services are inadequate. This is because the treatment of refractive errors is perhaps the simplest and most cost-effective healthcare interventions. Uncorrected refractive error in school children portends significant implications for a child's academic achievement as well as social interactions [8]. Poor vision has been correlated with poor academic performance [9]. In Egypt there are a few studies showing the prevalence of refractive errors. A survey conducted among 5839 Egyptian school children aged 7–15 years found that the prevalence of refractive errors (visual acuity ≤6/12) was 22.1% [10]. A preliminary national survey done in the Helwan area of Cairo reported that 34% of the recorded disabilities were visual disabilities [11].


The aim of the present study was the detection and estimation of refractive errors among school children aged 11–15-year old in Tanta, Gharbia, Egypt, to allow for early correction of diagnosed children.

  Patients and Methods Top


This was a cross-sectional study. Tanta city is divided into two districts ( first, second). The calculated sample was chosen from the total number of students in Tanta schools

In total, 1258 students were chosen randomly out of the total students in the chosen 10 schools from the two districts of Tanta city.

Sample size

The total number of patients to be selected was estimated using the following equation: n = (z2 × p × q)/D2 at power 80% and 95% confidence interval; finally, the sample size was calculated to be 1258.

Children aged 11–15 years at different public and private schools in Tanta city were included in the study. Twenty-five classes were randomly selected from 10 schools, eight public and two private, in Tanta. The field work was carried out between December 2015 and March 2016. A total of 1272 students were examined.

Inclusion criteria

The students were selected by using the random sampling technique from schools of Tanta city for detection of refractive errors.

Exclusion criteria

Any other causes of visual acuity decrease rather than refractive errors were excluded from the study.


At school

Visual acuity, external eye examination, and autorefraction were assessed. Those diagnosed to have any refractive errors were referred to Tanta ophthalmology hospital for glasses prescription.

The proposal of the study was reviewed by the Ethical Committee in Faculty of Medicine. Administrative approval letters were taken from Gharbia Directorate of Education. A questionnaire and a written consent were distributed to the students in the selected class rooms to take the approval of the students' parents.

Students were subjected to a full and detailed history taking, including personal history (age, sex, residential address, socioeconomic condition), complaints if present, and past history (medications, trauma, or ocular surgery). Parents also were asked about wearing glasses. Examinations carried out were as follows:

  • External examination: During history taking, we judged:

    1. Alertness level
    2. Gross ocular alignment
    3. Head posture orbits (appraised for ptosis, abnormalities in fissure size or shape, and orbital depth)

  • Visual acuity testing (with and without correction): Visual acuity is the easiest to perform and most important test of visual function

  • Landolt C chart, the broken ring optotype is made with a 'C' like. The patients have to indicate the orientation of the gap (left, right, up, and down)

  • Examination of pupillary reaction and near reflex: It is important to rule out an afferent pupillary defect, especially with unilateral visual loss or strabismus. The swinging flashlight test was routinely used. In addition, near reflex was examined for all students
  • Red reflex: Evaluation and binocular comparison of the red reflex are valuable in assessing media opacities or refractive aberrancies. It is best performed using the Bruckner modification, which is simply a simultaneous bilateral red reflex; in dim illumination, by staying far enough away from the child, both pupils of the child are illuminated with the same direct ophthalmoscope beam and then the quality and intensity of reflexes between the two eyes are compared. It is started with the ophthalmoscope on low illumination, and then slowly the illumination is increased until red reflex is seen
  • Autorefraction: It was assessed by using an autorefractometer.

Statistical analysis

Results were statistically analyzed by SPSS (version 20; SPSS Inc., Chicago, Illinois, USA). Student's t test was used for parametric data. The c2 test was used for qualitative variables. value less than 0.05 was considered significant.

  Results Top

Out of the selected 1272 children, 812 (63.8%) were girls and 460 (36.2%) were boys; 534 (42%) children were from private schools and 738 (58%) from public schools. Mean±SD age of the children was 13.14 ± 0.91 years. Family history of refractive errors was (63.1%) positive [Table 1]. In this study other ocular diseases were found during examination. In total, 308 children had other eye diseases and these diseases were allergic conjunctivitis, which represented 55.8% of this cases, amblyopia (35%), strabismus (2.5%), eyelid chalazae (0.3%), trachoma (1.3%), mucopurulant conjunctivitis (3.5%) congenital anomalies (microcornea) (0.3%) [Table 1].
Table  1: Distribution of the studied children regarding their characteristics and other ocular diseases

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Refractive errors were present in 868 (68.2%) children. Myopia was the most common error, present in 704 (55.3%) children, followed by astigmatism [648 (51%) children] and hypermetropia [144 (11.4%) children] [Table 2]. Overall 33.6% children had visual acuity 6/6 in the right eye and 34.9% had it in the left eye, whereas 31.7% children had visual acuity 6/6 in both eyes. Most of the children had visual acuity of 6/9; 3.5% had a visual acuity of 6/60 and counting fingers (CF) was detected in 0.6% children [Table 3]. The mean ± SD age of showing refractive errors was 13.08 ± 0.5 [Table 4]. According to sex, myopia was present in 260 (56.5%) boys and 444 (54.6%) girls. Hypermetropia was present in 36 (7.8%) boys and 108 (13.3%) girls. Astigmatism was present in 208 (45.2%) boys and 440 (54.1%) girls [Table 5]. The percentage of refractive errors was almost the same in private and public schools [Table 6].
Table  2: Distribution of the studied children regarding refractive error and its types

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Table  3: Distribution of the studied children regarding their visual acuity

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Table  4: Distribution of refraction errors its types regarding age

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Table  5: Distribution of refraction errors types regarding sex

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Table  6: Distribution of refraction error its types regarding school

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One of the most important results found was the prevalence of amblyopia. Amblyopia represented 12% of the total children who had errors, and 8% of all children. Anisometropia was 1.8% of children with errors [Figure 1] and [Figure 2].
Figure  1: Prevalence of amblyopia among school children.

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Figure  2: Prevalence of amblyopia regarding school children errors.

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  Discussion Top

School screening programs have been an established part of the school health service since 1907 and remain universally recommended. These programs are primarily aimed at detecting amblyopia and refractive errors.

In our study children aged 11–15 years at different public and private schools in Tanta city were included in the study. Twenty-five classes were randomly selected from 10 schools, eight public and two private, in Tanta, Gharbia government. The field work was carried out between December 2015 and March 2016. A total of 1272 students were examined.

In our study, 68.2% children had a refractive error of ± 0.5 or worse in one or both eyes and needed glasses. Among refractive errors, myopia was the most common (55.3%) followed by hypermetropia (11.4%); this was higher compared with other studies carried out in other regions as in Cairo (22.1% of students aged 7–14 years) [10]; this may be attributed to lake of awareness of the parents of testing their children's vision and only when conditions are severe as to be noticed by the parents or teachers that ophthalmological examination is performed. These results are near to a study carried out in Assiut in 2014 (66.9%). In our study, astigmatism was detected among 51% of the examined students with or without other refractive errors; this was higher than that reported in New Delhi 2002 as astigmatism accounted for 10.3% of all errors.

In our study refractive errors were more common among children who had a positive family history of wearing glasses, with one or more of their parents; this may support the theory of genetic factor as in OMIN [12].

Furthermore, in our study only 31% children wore glasses and this indicated a lack of awareness about the importance of regular eye examination of children, even the highly educated ones.

In our study amblyopia was detected in 8% of children; this explained the importance of early diagnosis of refractive errors in early childhood. Anisometropia was present in 1.8% of the children.

Refractive errors were shown to be the leading cause of visual impairment among school children as reported in numerous studies. But many young children with such conditions are asymptomatic. Visual screening can be useful for detecting asymptomatic visual problems; however, compliance with spectacle wearing may be very low for many reasons, such as forgetting to wear glasses, concern about appearance, or not feeling that glasses are needed [13].

Because most refractive errors can be corrected in early life and because visual impairment can have a detrimental impact on education and development in a child's life, cost-effective strategies to eliminate this easily treatable cause of visual impairment are warranted [6].

From our findings, 26.6% of the students previously went to the ophthalmologists for follow-up and eye inflammations, with none of them wearing eyeglasses. This may reflect social stigmatization of spectacles. Furthermore, there are some misconceptions regarding wearing eyeglasses at young age, as it associated or may lead to blindness later on. The prevalence of refractive errors from eye screening in school children worldwide has been found to be 10–40% [14].

The prevalence of abnormal visual acuity in general population of children aged 7–8 years in Poland was estimated on the basis of results from a studied sample on the level of 17.7 ± 5.0% for 95% confidence interval and was in the range 12.3–24.9% [15].

In the year 2005 Muszyńska-Lachota et al. [16] studied 138 children 7–8 years of age from the West Pomeranian region, Poland, demonstrating that among 7-year-old children, hypermetropia was the dominating refraction error affecting 75% of the girls and 75.3% of the boys. Myopia was detected in 3.2% girls and 2.5% boys. Among 8-year-old children, hypermetropia was also a common problem (80.8% girls and 74.1% boys); astigmatism was shown in 2.1% girls and 3.7% boys. The prevalence of particular refraction errors among both age groups showed no statistically significant difference [16].

Myopia and astigmatism were 65 and 16.1%, respectively [6]. Myopia was found to be the most common type of refractive error among Malaysian children aged 6–12 years, with a prevalence of 5.4%, followed by hyperopia (1.0%) and astigmatism (0.6%). A significant positive correlation was noted between myopia development with increasing age, more hours spent on reading books, and background history of siblings with glasses and whose parents are of higher educational level [17].

One hundred seven of the 122 (87.7%) patients were considered to have a refractive error with or without one or more other eye conditions [18]. Cross-sectional studies have also found a positive association between myopia and near-work activity such as reading and writing. Overall, 60.7% of myopic students watched television for less than 1 h and about one-third of them watched it at a distance of 1–2 m. These findings may be explained by the fact that myopia made the students watch television for a shorter duration and at close distance compared with other students [19],[20],[21],[22].

Hashim et al. [17] found that myopia was the most common type of refractive error, detected in 38 students, contributing 77.5% of the total refractive errors. The prevalence of myopia was 5.4% in the study population. Hyperopia was detected in seven (1%) students, followed by astigmatism in four (0.6%) students. There was a statistically significant association of students in the upper primary group, longer hours spent for reading books, background history of siblings with glasses, parent's educational level, and household income in the development of myopia. There was no significant association between myopia development and the history of parents with glasses [Figure 3] [23],[24],[25],[26],[27],[28].
Figure  3: Prevalence of myopia worldwide.

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  Conclusion Top

Refractive errors affected approximately more than half of the students. Myopia was the more frequent refractive problem. Most of the children are unaware of their refractive errors. The majority of the students were never examined for visual acuity. Most refractive errors can be corrected early in the life. Therefore, every child should receive eye examination by an ophthalmologist at school entrance.

Financial support and sponsorship


Conflicts of interest

There are no conflicts of interest.

  References Top

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  [Figure 1], [Figure 2], [Figure 3]

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]


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