Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 29  |  Issue : 2  |  Page : 94-100

Prevalence of Refractive Errors and the Impact of Its Correction on Academic Performance of Primary School Children in Nigeria


1 Senior Registrar, Department of Ophthalmology, University of Ilorin Teaching Hospital, Nigeria
2 Professor of Paediatric Ophthalmology, University of Ilorin Teaching Hospital, Nigeria
3 Professor of Ophthalmology, University of Ilorin Teaching Hospital, Nigeria
4 Office of Education Quality Assurance, Ministry of Education, Lagos State, Nigeria

Date of Submission08-Apr-2020
Date of Decision16-Jul-2020
Date of Acceptance01-Sep-2020
Date of Web Publication18-Jan-2022

Correspondence Address:
S O Akinremi
Senior Registrar, Department of Ophthalmology, University of Ilorin Teaching Hospital
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njo.njo_13_20

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  Abstract 


Background: Vision is critical to optimal educational development. About 12 million children are affected with undetected visual impairment from refractive error and are mostly in Asia and Africa, hence the need to determine the prevalence of refractive error and the impact of its correction on academic performance (AP) in a representative cohort of African children in Ilorin, Kwara State, and Nigeria. Few published studies have looked at the impact of refractive error on AP in Nigeria. This study will afford the children to have vision screening and correction of their refractive errors. It will also reinforce the importance and need for vision screening among primary school pupils and increasing teachers and parents awareness. Methodology: This was a quasi-experimental study carried out among 2124 primary school pupils aged 5–15 years. Eye examination and refraction were carried out during the first term of the school academic calendar. Children with visual acuity worse than logMar 0.2 (6/9.5), which improves with pinhole, had refraction and were dispensed free eyeglasses. The AP of pupils with refractive error was assessed at the end of the first term before the use of eyeglasses and at third term after wearing eyeglasses for 6 months using the mean academic score for all subjects. Result: The prevalence of refractive errors among primary school pupils aged 5–15 years was 2.8%. Myopia was the most common refractive error with a prevalence of 1.2%. The change in mean academic score of pupils with refractive errors was statistically significant as it improved to 61.1 ± 13.4 from 56.5 ± 13.9 following the use of eyeglasses. The improvement in AP was more significant in pupils with hypermetropia and astigmatism following the use of eyeglasses. Conclusion: The average AP of pupils with refractive errors was good, but nevertheless correcting for refractive errors had a positive impact, especially in pupils with hypermetropia and astigmatism.

Keywords: Academic performance, children, refractive error


How to cite this article:
Akinremi S O, Ademola-Popoola D S, Olatunji F O, Ogunmuyiwa S O. Prevalence of Refractive Errors and the Impact of Its Correction on Academic Performance of Primary School Children in Nigeria. Niger J Ophthalmol 2021;29:94-100

How to cite this URL:
Akinremi S O, Ademola-Popoola D S, Olatunji F O, Ogunmuyiwa S O. Prevalence of Refractive Errors and the Impact of Its Correction on Academic Performance of Primary School Children in Nigeria. Niger J Ophthalmol [serial online] 2021 [cited 2022 May 22];29:94-100. Available from: http://www.nigerianjournalofophthalmology.com/text.asp?2021/29/2/94/335913




  Introduction Top


Vision in children plays a fundamental role in the acquisition of skills such as language, facial expressions interpretation, and skills requiring hand-eye coordination.[1] Undetected refractive error in children can affect their abilities to make informed choices and to learn from the environment, thus reducing their ability to explore the environment. World Health Organization’s Vision 2020 estimated that 12 million children between the ages of 5 and 15 years have undetected visual impairment from refractive error, which could result in low self-esteem and emotional instability.[2],[3]

Academic performance (AP) is the extent to which a student has achieved his or her educational goals, and it is often measured by examinations or continuous assessments.[4] Some other factors influencing AP include individual differences, level of intelligence,personality type, parents’ socioeconomic status, teachers’ competence, type of school, and home environment.[5],[6],[7],[8] Studies have found that a high level of intelligence, high parents’ socioeconomic status, and teachers’ competence are factors that improve a child’s school performance.

Studies have reported conflicting results on the effect of uncorrected and corrected refractive errors on AP, hence the need to carry out a study to assess the impact of refractive error correction on AP. In addition, parents of children with refractive error have also complained in the clinic about their wards’ poor AP. Thus, this study will help improve our understanding of the relationship between this ocular condition and AP.

Hence, the need to ask the question: “Does refractive error affect the AP of primary school children?” The aim of this study was to determine the impact of refractive error correction on AP of primary school children in Ilorin East Local Government with a view to improve their AP.


  Materials And Methods Top


A quasi-experimental study was conducted among 2153 primary school pupils between the ages of 5 and 15 years in Ilorin East Local Government, which consist of both urban and rural settlement. The study duration was from November 2016 to July 2017.

Sample size calculation: The minimum sample size was calculated using the Fisher formula.[9]



Here, n is the minimum sample size, z is the standard normal deviation, which is 1.96 and corresponds to the 95% confidence level, and p is the prevalence of refractive error in a previous study done in Ilorin by Ayanniyi et al.[10] Its value is 6.9%, and thus p is 0.069, q = 1–0.069 = 0.93; d is the degree of accuracy desired, which is set at 0.02.



n = 616

After adjusting for the attrition rate of 10%, the calculated minimum sample size for the study was 678. The pilot study suggested that the percentage of pupils with confirmed refractive errors would be less than 6.9% as in the previous local study. Thus, minimum sample size was increased by about 60% in order to yield more pupils with refractive errors. A total of 2153 children were thus recruited, while 29 were excluded for not meeting the inclusion criteria, leaving a 2124 sample size for the study.

Sampling technique

There are 79 public primary schools and 75 private primary schools in the local government area (LGA), with a total student population of 40,815 (22,289 and 18,525, respectively).[11] Primary school enrolment of public and private ratio was 1.2:1, while the number of school pupils included in this study was 2153 at a ratio of 1370:804 pupil from public and private schools, respectively. The average mean of enrolment was 268, which was derived by dividing the number of schools by the student population and this formed our cluster size.

An alphabetical listing of schools with their enrolment formed the sampling frame, and computer generated random number was used to determine the first school to be included from the list of schools. After the first school, every seventh school from the first school was chosen and their population added together until the sample size was reached. In schools where enrolment was greater than the cluster size, only 268 pupils were examined in that school using stratified sampling, proportion-to-size technique, and table of random number to determine the number of pupils to be selected in each class. In schools where the population was less than the cluster size, all pupils who met the inclusion criteria were recruited into the study.

A written approval to carry out the study at selected school was given by the local government, while ethical approval was obtained from the ethical board of University of Ilorin Teaching Hospital. Signed parental content and both verbal and signed assent forms were gotten from pupils aged 7 to 15 years. Pupils with visual impairment not correctable with refraction or pupils already using spectacles or those with learning difficulties from chromosomal/central nervous system (CNS) identifiable problems were excluded.

Clinical evaluation was carried out at first term of the school academic calendar using modified standardized questionnaires, which was carried out by the ophthalmic assistant.[12],[13] The questionnaire had section on biodata, ocular symptoms, vision assessment, eye examination, refraction, and pre- and posttreatment academic assessment. During the presurvey activities, the head teacher selected two teachers who were trained and who were assisted by the ophthalmic assistant in carrying out the visual acuity (VA). The VA test was done by setting up the Teacher-LED Vision Screening Kit.[14] The referrals by the teachers were cross-checked to validate their findings by the researcher before refraction. The VA reading chart was set at 3 meters.

Pupils found to have VA worse than logMAR 0.2 (6/9.5) and who had an improvement with pinhole had cycloplegic refraction done using 1% cyclopentolate eye drop and a postcycloplegic refraction was done a week later at the various schools. The required glasses were dispensed at no cost to the affected pupils after counselling the pupils and teachers. There were follow-up phone calls to parents and teachers to ensure and monitor compliance. Other pupils found to have ocular disorders were either treated at the screening site or referred to nearest tertiary eye clinic at the University of Ilorin Teaching Hospital for further assessment and treatment.

To determine the child’s AP, the percentage mean academic score was calculated from the continuous assessment booklet, and the scores were situated within different categories, 0%–39%, 40%–49%, 50%–59%, 60%–69%, and above 70%,[15] using the percentage mean academic score for all subjects. The AP of the children with refractive error was assessed at the end of first term examination using the mean academic score in their continuous assessment and compared with their third term mean academic score after using their eyeglasses for 6 months. These data were collated by the education assistant, who is a member of the reach team from the head teacher.

In this study, myopia was defined as a refractive error corrected by a sphere of at least −0.50D, while hypermetropia was defined as a refractive error corrected by a sphere of +0.50D and above, which improves vision. Astigmatism was defined as a refractive error corrected by a cylindrical lens of ≥0.25DC alone or with a sphere to achieve good vision.

Following data collection and entry, statistical analysis was performed using IBM-SPSS-20 (Armonk, NY: IBM Corp 2011). An initial frequency count of variables was performed, and relevant mean, range, and standard deviations were deduced. The association between continuous variables was determined with student t test and analysis of variance (ANOVA). Student t test was used to determine whether there was a relationship between the pre- and posttreatment of refractive errors and AP. P < 0.05 was considered statistically significant.


  Results Top


A total of 2153 pupils were recruited as part of the 12 cohorts that formed the study population. Twenty-nine pupils (1.3%) were thereafter excluded because they fell short of the inclusion criteria. The age range was 5 to 15 years, with the mean age of 9.2 ± 2.2. The highest number of children screened was between the ages of 9 and 10 years (28.8%). Gender was almost equitably distributed with a ratio of ratio 1:1 [Table 1].
Table 1 Age and gender distribution of 2124 primary school pupils screened

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Out of the 2124 pupils screened, refractive errors were found in 116 eyes of 60 pupils, giving a prevalence of 2.8% [Table 2], although the prevalence of refractive errors was higher among pupils in urban communities.
Table 2 Prevalence of refractive errors in different neighborhood among primary school pupils

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All the 25 (41.7%) pupils with myopia had simple myopia with the range from −–0.50 to −–3.00D Dioptres and this was the most common refractive error ([Figure 1).]. The type of refractive error in the right eye was used in making the diagnosis. Anisometropia this was diagnosed in 8 eight (13.3%) children. Majority (47, 78%) of the children with refractive error were found among children aged 7-–12 years, ([Figure 2).].
Figure 1 Types of refractive error in the 60 children with refractive error

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Figure 2 Age distribution of children with refractive error

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[Table 3] shows the magnitude of different types of refractive error per eye among the various age groups in this study. The age group most affected by refractive error was that of children between the ages of 9 to and 12 years. However, these findings were not statistically significant.
Table 3 Magnitude of different types of refractive error among various age groups in pupils with refractive error

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AP was assessed only in 56 pupils because four (6.7%) pupils were excluded from completing the study due to change in school. This gave the study a participation figure of 56 (93.3%) pupils. Thirty-eight pupils (67.9%) had a mean academic score of 50 and above, while 18 (32.1%) had a mean academic score below 50 before treatment, when compared to 45 (80.4%) pupils who had 50 and above in their AP 6 months after using eyeglasses [Table 4]. The gross increase in the mean academic score before and after the use of eyeglasses showed a statistically significant improvement from 56.5 ± 13.9 to 61.1 ± 13.4, with a P < 0.001 [Table 5]. Pupils with corrected hypermetropia and astigmatism had a statistically significant improvement in their AP unlike pupils with myopia [Table 6].
Table 4 Academic performance grade before and after treatment in pupils with refractive error

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Table 5 Mean AP before and after treatment in children with refractive error

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Table 6 Comparison of AP of children pre- and posteyeglasses use for different types of refractive error

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Extracurricular activities engaged in by pupils after school hours include learning skills, trading, attending Arabic classes, and home coaching classes. Thirty-nine (69.6%) pupils with refractive errors engaged in some extracurricular activities and the most common extracurricular activity among the pupils with refractive error was trading (14, 25%) and followed by coaching classes (11 pupils, 19.6%) [Table 7].
Table 7 Extracurricular activities engaged in by pupils with refractive error before and after treatment

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Pupils who engaged in after school coaching classes and those who were not involved in any extracurricular activities had a significant improvement in their academic score than pupils who were involved in other forms of activities after 6 months of spectacle use [Table 8].
Table 8 Comparison of the academic performance of pupils who engaged in extracurricular activities pre- and posteyeglasses use at third term

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Compliance with the use of glasses was monitored by making three phone calls to the school within the period of the study. Compliance is said to be good if the child is found to be wearing the glasses at least least twice out of the three times the phone call was made. Forty-seven pupils (83.9%) were found to be compliant with the use of their glasses, while nine pupils (16.1%) were not compliant. The schools (and teachers) were able to achieve and sustain compliance by sending the pupils back home to bring their glasses to school and ensuring the use of the glasses during class work or assisting in keeping the glasses in school to prevent damage or loss.


  Discussion Top


The prevalence of refractive error in this study is similar to the 2.2% found by Opubiri and Pedro-Egbe[16] in Bayelsa State, Nigeria among pupils aged 5 to 15 years old. The prevalence is low when compared to other similar studies in Nigeria such as Ajaiyeoba et al.[17] in southwest Nigeria (5.8%) who assessed older children between the ages of 4 and 24 years. Ayanniyi et al.[10] in Ilorin (north central Nigeria) found a prevalence of 6.9%, which is probably because they estimated only refractive from pinhole assessment, whereas this study reflects a true situation from refraction and improvement in VA with eyeglasses. Abah et al.[18] in Kaduna (northwest Nigeria) reported a much higher prevalence of 8.0% with a sample size of 327. The high prevalence reported by Abah et al. could be because the study took place in an urban community and subjective refraction was not done.

Similarly to this study, Mehari and Yimer[19] in Ethiopia and Shankar et al.[20] in Nepal reported myopia as the most common refractive error, although with varying degree of prevalence, which could be due to the slightly older age range of the study population, which was 7–18 years and 5–16 years, respectively, and children already using eyeglasses were not excluded unlike in our study. The mean academic score of pupils with refractive error was 56.54 ± 13.95. Children with myopia had the highest academic score when compared to children with other forms of refractive error. This could be because myopes have preference for near work and the absence of asthenopic symptoms allows them to spend longer time reading. The mean AP of myopes was 59.52 ± 14.49, while astigmatic and hypermetropic children had 54.85 ± 13.95 and 53.85 ± 13.00 before eyeglasses, respectively. This is supported by a study by Basu et al.[21] in a cross-sectional study among female students in India between the ages of 7 and 15 years that 75.9% of children with refractive error had good AP. Carolina et al.[22] observed in a cross-sectional study involving 222 students aged 8–10 years that 25% of students with VA of 0.7 (6/30) had unsatisfactory performance. However, Kotingo et al.[15] observed among children with reduced VA that only 42% of children with reduced VA had good AP while 58% had poor AP.

There was a statistically significant improvement in the mean academic score with a P < 0.05. This finding is supported by Pavithra et al.,[23] who observed that 87.5% of children who were consistent with the use of eyeglasses had an improvement in school-related activities. Joseph[24] also found a significant difference in the AP of children with refractive error following the use of glasses.

This study also found a statistically significant improvement in the mean academic score of children with hypermetropia and astigmatism following correction with eyeglasses, unlike children with myopia who had some degree of improvement but was not significant statistically. This could be because myopes tend to prefer indoor activities, which are carried out at a close range and do not have asthenopic symptoms when studying unlike pupils with hypermetropia or astigmatism. Similarly, Ma et al.[25] assessed the effect of providing free glasses to children’s educational outcomes in China where 19,934 children between the ages of 9 and 12 years were screened. They also found a statistically significant impact of providing glasses on AP of children with refractive error despite unsatisfactory compliance.

Confounding factors that could influence AP include extracurricular activities and chronic absenteeism from school. In this study, those pupils who were involved in extracurricular coaching classes had a statistically significant improvement in their AP following the use of spectacle than those who were involved in other extracurricular activities such as skill acquisition. Chronic absenteeism, which means missing more than 10% of the school academic year for any reason, has been proven to be a cause of low AP.[26] In this study, none of the pupils with refractive error was observed to be absent from school for more than 10% of the year. Chronic absenteeism therefore could not have been a cause of bias in this study.

The limitation of this study includes not looking at the impact of study time, competence of teachers, and comparing the AP of pupils with refractive error to the AP of other pupils without refractive error.


  Conclusion Top


Myopia was the commonest types of refractive error seen in the study population. Pupils with uncorrected myopia had the best AP. The correction of refractive error with eyeglasses significantly improved the AP of pupils with hypermetropia and astigmatism, Therefore, the need for school eye screening program with teachers taking a lead in early detection and treatment of refractive errors by eye care team is emphasized.

Financial support and sponsorship

Nil.Conflicts of Interest

There are no conflicts of interest.



 
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Ayanniyi AA, Mahmoud AO, Olatunji FO. Causes and prevalence of ocular morbidity among primary school children in Ilorin, Nigeria. Niger J Clin Pract 2010;13:248-53.  Back to cited text no. 10
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List of schools enrolment was gotten from the office of the Kwara state universal basic education board. 2016.  Back to cited text no. 11
    
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Opubiri I, Pedro-Egbe CN. Screening of primary school children for refractive error in South-South Nigeria. Ethiop J Health Sci 2012;22:129-34.  Back to cited text no. 16
    
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Pavithra MB, Hamsa L, Madhukumar S. Factors associated with spectacle-wear compliance among school children of 7-15 years in South India. Int J Med Public Heal 2014;4:146.  Back to cited text no. 23
    
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Ma X, Zhou Z, Yi H, Pang X, Shi Y, Chen Q et al. Effect of providing free glasses on children’s educational outcomes in China: cluster randomized controlled trial. BMJ 2014;349:g5740.  Back to cited text no. 25
    
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