Table of Contents  
ORIGINAL ARTICLE
Year : 2018  |  Volume : 26  |  Issue : 1  |  Page : 67-73

Risk factors associated with amblyopia among primary school pupils in Kosofe town, Lagos state, Nigeria


1 Ancilla Catholic Hospital Eye Centre, Agege, Nigeria
2 Department of Ophthalmology (Guinness Eye Centre), Lagos University Teaching Hospital/College of Medicine of the University of Lagos, Idi-Araba, Lagos, Nigeria

Date of Web Publication5-Sep-2018

Correspondence Address:
Dr. Segun J Ikuomenisan
Ancilla Catholic Hospital Eye Centre, Agege, Lagos
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/njo.njo_29_17

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  Abstract 


Aim: To investigate the risk factors associated with amblyopia among primary school pupils in Kosofe town, Lagos State, Nigeria. Materials and Methods: A descriptive, cross-sectional, school-based study was conducted, in which a multistage random sampling technique was employed for recruiting the children. Data were collected using self-administered questionnaires by the parents or caregivers and from detailed ocular examinations performed by the investigators. Data analysis was performed using the IBM Statistical Package for Social Sciences software version 20.0. Results: A total of 1702 children participated in the study, with over 90% of the children being aged 4–10 years. Most (78.5%) of the mothers were aged 20–39 years at childbirth, and the mean age was 30.5 ± 7.8 years. Amblyopia was detected in 24 (1.41%) children. Following multivariate logistic regression analysis, children whose mothers had no formal education at childbirth had an 11-fold greater risk of having amblyopia [odds ratios (OR) = 11.25, 95% confidence intervals (95% CI) = 1.25–1.49], while those with birth weight <2500 g were 10 times more likely to have amblyopia at the time of examination (OR = 10.15, 95% CI = 0.70–0.90). In addition, children with a positive family history of crossed eyes had an eightfold greater risk of having amblyopia (OR = 8.14, 95% CI = 0.24–0.46). Conclusion: Mother’s educational qualification at childbirth, low birth weight, and a positive family history of crossed eye were found to be strongly associated with the development of amblyopia.

Keywords: Amblyopia, primary school pupils, risk factors


How to cite this article:
Ikuomenisan SJ, Musa KO, Aribaba OT, Onakoya AO. Risk factors associated with amblyopia among primary school pupils in Kosofe town, Lagos state, Nigeria. Niger J Ophthalmol 2018;26:67-73

How to cite this URL:
Ikuomenisan SJ, Musa KO, Aribaba OT, Onakoya AO. Risk factors associated with amblyopia among primary school pupils in Kosofe town, Lagos state, Nigeria. Niger J Ophthalmol [serial online] 2018 [cited 2023 Feb 6];26:67-73. Available from: http://www.nigerianjournalofophthalmology.com/text.asp?2018/26/1/67/240446




  Introduction Top


Amblyopia is a disorder of the visual system that is characterized by a decrease in the best-corrected visual acuity (BCVA) in an eye with no organic pathology.[1],[2],[3] There is no obvious ocular pathology underlying the reduced visual acuity (VA), but rather, there are some predisposing conditions that influence the development of VA after birth.[2]

Amblyopia is at least four times more common in children who were premature or small for their gestational age.[4],[5],[6] Robaei et al.[4] reported that children born at <37 weeks of gestation had a fivefold risk of having amblyopia, while those with birth weights <2500 g were almost five times more likely to have amblyopia at the time of examination. Mohammad et al.[5] during a cross-sectional study of 164 children aged 5–10 years, who were referred to an amblyopia clinic in Iran, showed a significant association between amblyopia and low birth weight (LBW), preterm birth, as well as dystocia. Saunders et al.[6] reported that premature birth carries a risk of abnormal refractive development, because early emmetropization process differed in preterm infants from that of the full-term infants. Robaei et al.[4] also found that admission into a neonatal intensive care unit conferred a fivefold increased risk of developing amblyopia. However, amblyopia was not associated with LBW, preterm birth, maternal age, or maternal smoking during pregnancy in the Strabismus, Amblyopia, and Refractive Error in Young Singaporean Children (STARS) study[7] and the Sydney Paediatric Eye Disease Study (SPEDS).[8] Factors such as maternal smoking, drugs, and alcohol use during pregnancy may be associated with an increased risk of amblyopia.[9],[10]

There are few studies on amblyopia in our community, and the majority did not investigate its associated factors. The effects of the mother’s socioeconomic status, pregnancy and birth, and developmental, familial, and past ocular histories on the pattern of amblyopia in our community need to be adequately studied. This study investigates the risk factors associated with amblyopia among primary school pupils in Kosofe town with a view to identifying the modifiable ones for which preventive measures could be suggested. The following factors were assessed: mother’s socioeconomic characteristics at birth, family’s ocular history, past medical/ocular history, as well as pregnancy, birth, and early developmental history.


  Materials and Methods Top


A detailed description of the methodology used in this study has been published earlier.[11] This descriptive, cross-sectional study was conducted among 41 primary schools (21 public and 20 private) in Kosofe Township, Lagos, Nigeria during a nine-month period. Ethical approval was obtained from the Health Research and Ethics Committee of the Lagos University Teaching Hospital as well as the Lagos State Universal Basic Education Board prior to the commencement of this study. Written informed consent from the schools’ head teachers and the parents of selected schools were also obtained before screening their wards. The research protocol adhered to the provision of the Declaration of Helsinki for research involving human beings.

Using a reported prevalence of amblyopia at 3.1[12] and 10% nonresponse, the calculated sample size was 1794. A multistage random sampling system was employed in recruiting the pupils. Presurvey training was conducted to enable the team to familiarize with the standard operating procedures involved in the study. Pilot studies were conducted in two schools (one government and one private) to validate the data collection forms and to minimize interobserver variations. The selected children were enumerated and given copies of the consent forms and questionnaires to take home with them. The questionnaires were used to collect detailed information on ethnicity, parental education, the place of residence, parent’s occupation, ocular history, a history of prematurity, birth weight, a history of eye and vision abnormalities in first-degree family members, and a history of past and present medical problems. The questionnaires were serially numbered to avoid duplication. Efforts were made to obtain the telephone numbers of these parents/caregivers from the children or schoolteachers. Telephone communications were employed to inform the parents/caregivers of the study and encourage them to sign the consent forms, fill the questionnaires, and send them back through their children or wards.

VA tests were performed in each eye with the HOTV chart from a distance of 3 m. Pupils who had an unaided VA of <6/9 in at least one eye. Subsequently, refraction was done 30 min after the instillation of three drops of 1% cyclopentolate administered at 5-min intervals. Refraction was measured with a table-mounted autorefractor (Topcon 80,00®, Japan) whenever possible, or streak retinoscope (WelchAllyn RF18240, New York) when autorefraction was not possible. Five consecutive autorefractor readings were obtained from each participant, all of which had to be within 0.25 Diopter Sphere (DS) of each other. Postcycloplegic refraction was performed to determine the BCVA of the pupils. Ocular alignment was assessed using the Hirschberg light reflex, cover test, and prism cover–uncover test. The pupils underwent full ocular examination, and any pathology involving the anterior and posterior ocular segments were documented.

Unilateral amblyopia was defined as a ≥2-line difference in BCVA, when <6/9 in the worse eye, and with amblyogenic factors such as past or present strabismus, anisometropia (≥1.00 DS difference in hyperopia, ≥3.00 DS difference in myopia, or ≥1.50 DS difference in astigmatism), and the past or present obstruction of the visual axis.[7],[13],[14] Bilateral amblyopia was defined as BCVA in both eyes of <6/12 in the presence of amblyogenic factors such as hyperopia ≥4.00 DS, myopia ≥−6.00 DS, or astigmatism ≥2.50 DS, or the past or present obstruction of the visual axis.[7],[13],[14] LBW was defined as birth weight <2500 g, while prematurity was defined as gestational age <37 weeks.[4],[5],[8]

The data obtained were entered into a database and analyzed using the IBM Statistical Package for Social Sciences software version 20.0 (IBM Corp., Armonk, NY). Descriptive statistics including frequencies, means, and standard deviations were generated to observe the distribution of sociodemographic and medical factors. Bivariate analyses were conducted with the use of cross-tables and chi-squared tests, whereas multivariate analysis was conducted using the logistic regression model to evaluate associations between variables. We report adjusted odds ratios (OR) and 95% confidence intervals (95% CI) for the following variables: mother’s occupation at childbirth, mothers’ educational qualifications at childbirth, birth weight, developmental milestones, a history of past eye complaints, a history of past spectacle use, a history of past ocular surgeries, a family history of wearing glasses, a family history of eye surgery, and a family history of crossed eyes. Analyses were considered to show statistically significant associations, when the P-values were <0.05.


  Results Top


Of the 1794 pupils eligible for this study, 1702 pupils were fully examined, representing a study completion rate of 94.9%. There were 899 male (52.8%) and 803 female (47.2%) students, with a male-to-female ratio of 1.1: 1. The age range was from 4 to 16 years, and the mean age was 7.5 ± 1.6 years [Table 1].
Table 1: Age and sex distribution of the screened children

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The age range of the mothers was from 17 to 55 years, while their mean age was 30.5 ± 7.8 years. Self-employed mothers accounted for 33.7%, 25.7% were civil servants, and 7.8% had no formal education at childbirth [Table 2]. Six hundred and sixty-nine (39.3%) mothers were ill during pregnancy, 137 (8.1%) indulged in tobacco, cigarette, or alcohol intake during pregnancy, and 245 (14.4%) took non-antenatal medications. Most (91.9%) deliveries were full term, with 27.9% having LBW [Table 3].
Table 2: Socioeconomic characteristics of the mothers of screened children

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Table 3: Pregnancy, birth, and early developmental history of the screened children

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One thousand four hundred and twenty-five (83.7%) children have never worn spectacle, and 47 (2.8%) had a history of ocular surgery. Two hundred and four (12.0%) children had a positive family history of spectacle wear, 84 (4.9%) had for eye surgery, and only 71 (4.2%) had a family history of crossed eyes in their first-degree relatives [Table 4].
Table 4: Past medical and ocular history of the screened children

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The proportion of children with amblyopia was highest in those born to mothers in the age group of 20–39 years, but this was not statistically significant. The proportion of children with amblyopia was statistically significantly higher in children whose mothers were self-employed or who had no formal education at the time of childbirth [Table 5].
Table 5: Association between socioeconomic characteristics of mothers of screened children and amblyopia

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LBW was statistically significantly associated with amblyopia. Only 1 (3.6%) child born prematurely at <34 weeks had amblyopia, and this was not statistically significant [Table 6].
Table 6: Association among pregnancy, birth, and early developmental history of the screened children and amblyopia

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The prevalence of amblyopia was higher among children with a history of past eye complaints, spectacle use, and past ocular surgery [Table 7]. A family history of wearing glasses, eye surgery, and crossed eyes were statistically significantly associated with amblyopia [Table 8].
Table 7: Association between past medical and ocular history of the screened children and amblyopia

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Table 8: Association between family ocular history of the screened children and amblyopia

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On multivariate analysis of the statistically significant risk factor, children whose mothers had no formal education at childbirth had a 11-fold greater risk of having amblyopia (OR = 11.25, 95% CI = 1.25–1.49), while those with birth weight <2500 g were 10 times more likely to have amblyopia at the time of examination (OR = 10.15, 95% CI = 0.69–0.90) as shown in [Table 9]. In addition, children with a positive family history of crossed eyes also had an eightfold greater risk of having amblyopia (OR = 8.14, 95% CI = 0.24–0.46).
Table 9: Multivariate analysis (logistic regression) of risk factors for amblyopia

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  Discussion Top


This study found that mothers’ occupation at childbirth, mothers’ educational qualifications at childbirth, birth weight, a history of past eye complaints, a history of past spectacle use, a history of past ocular surgeries, a family history of wearing glasses, a family history of eye surgery, and a family history of crossed eyes were associated with amblyopia on bivariate analyses. However, only mothers’ educational qualifications at childbirth, LBW, and a positive family history of crossed eye were found to be strongly associated with the development of amblyopia following multivariate analysis.

There was a fairly equal enrollment of boys and girls into primary schools in this community (a male-to-female ratio of 1.1:1). This may be the result of public enlightenment on the advantages of educating the girl child. In this study, the children of mothers with no formal education at childbirth had an 11-fold risk of developing amblyopia. This compares favorably with the findings of The Joint Writing Committee for the Multiethnic Paediatric Eye Disease Study and the Baltimore Paediatric Eye Disease Study Groups, which reported that the lack of primary caregiver high school education was significantly associated with bilateral reduction in VA.[15] It is difficult to determine whether this association is the result of the poor performance of VA testing in the children of parents with no formal education or whether it is a true reflection of the state of amblyopia. On the other hand, Robaei et al.[4] in the Sydney Myopia Study and Pai et al.[8] in the SPEDS found no statistical association between amblyopia and the measures of socioeconomic status.

Children with LBW were 10 times more likely to have amblyopia in this study. The Sydney Myopia Study[4] found the odd of having amblyopia following LBW to be about fivefold (OR = 4.80, 95% CI = 1.90–11.80). This study also observed that children with a positive family history of crossed eyes had a fivefold greater risk of developing amblyopia. The STARS[7] study and the study by The Joint Writing Committee for the Multiethnic Paediatric Eye Disease Study and the Baltimore Paediatric Eye Disease Study Groups[16] established that strabismus was significantly associated with a positive family history of crossed eyes, but similar association was not established between amblyopia and a family history of squint. The study also found no association between LBW and amblyopia.

There are some limitations in this study. First, mothers may have selectively under- or overreported or may have forgotten some of the answers to the questions (especially the section on “history of pregnancy, birth and early development”) in the questionnaires. This recall bias may have some impact on the result of this study and may be attributable to the study design. Second, a finite number of potential risk factors were investigated. It is possible that other unknown or unexplored factors known to affect development (such as maternal diet during pregnancy, maternal exposure to ionizing radiation during pregnancy, and environmental toxins in pregnancy) could also contribute to amblyopia. The effect of non-schooling in children may also be a possible risk factor in amblyopia development. Thus, we recommend the need for further studies to investigate these unexplored factors.

In conclusion, the development of amblyopia was significantly associated with mother’s formal education, being LBW, and a positive family history of crossed eye. In the light of the foregoing, there should be increased awareness on the need to educate the girl child. Additionally, families with individuals having crossed eyes should be specially educated on the need for every child in the family to have regular and periodic eye examinations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
von Noorden GK, Campos EC. Binocular vision and ocular motility. In: Theory and Management of Strabismus. 6th ed. St. Louis: Mosby 2001. p. 246-7.  Back to cited text no. 1
    
2.
Chuka-Okosa MC. Amblyopia: Types, presentation and treatment − A review. Niger J Ophthalmol 2003;11:54-62.  Back to cited text no. 2
    
3.
Carlton J, Karnon J, Czoski-Murray C, Smith KJ, Marr J. The clinical effective and cost-effectiveness of screening programs for amblyopia and strabismus in children up to the age of 4–5 years: A systemic review and economic evaluation. Health Technol Assess 2008;12:1-194.  Back to cited text no. 3
    
4.
Robaei D, Rose K, Ojaimi E, Kifley A, Martin F, Mitchell P. Causes and associations of amblyopia in a population-based sample of 6-year-old Australian children. Arch Ophthalmol 2006;124:878-84.  Back to cited text no. 4
    
5.
Mohammad M, Masoud A, Hamid M, Ramak R. Associations of refractive amblyopia in a population of Iranian children. J Optom 2012;12:1-6.  Back to cited text no. 5
    
6.
Saunders KJ, McCulloch DL, Shepherd AJ, Wilkinson AG. Emmetropisation following preterm birth. Br J Ophthalmol 2002;86:1035-40.  Back to cited text no. 6
    
7.
Mohamed D, Yiong-Huak C, Gus G, Dana M, Seo-Wei L, Prabakaran S et al. Prevalence of refractive error in Singaporean Chinese children: The Strabismus, Amblyopia, and Refractive Error in Young Singaporean Children Study (STARS). Invest Ophthalmol Vis Sci 2010;51:1348-55.  Back to cited text no. 7
    
8.
Pai AS, Rose KA, Leone JF, Sharbini S, Burlutsky G, Varma R et al. Amblyopia prevalence and risk factors in Australian preschool children: The Sydney Paediatric Eye Disease Study (SPEDS). Ophthalmology 2012;119:138-44.  Back to cited text no. 8
    
9.
Lois N, Abdelkader E, Reglitz K, Garden C, Ayres JG. Environmental tobacco smoke exposure and eye disease. Br J Ophthalmol 2008;92:1304-10.  Back to cited text no. 9
    
10.
Bruce BB, Biousse V, Dean AL, Newman NJ. Neurologic and ophthalmic manifestation of fetal alcohol syndrome. Rev Neurol Dis 2009;6:13-20.  Back to cited text no. 10
    
11.
Ikuomenisan SJ, Musa KO, Aribaba OT, Onakoya AO. Prevalence and pattern of amblyopia among primary school pupils in Kosofe Town, Lagos State, Nigeria. Niger Postgrad Med J 2016;23:196-201.  Back to cited text no. 11
[PUBMED]  [Full text]  
12.
Adegbehingbe BO, Oladehinde MK, Majengbasan TO, Onakpoya HO, Osagiede EO. Screening of adolescents for eye diseases in Nigerian high schools. Ghana Med J 2005;39:138-42.  Back to cited text no. 12
    
13.
Multi-ethnic Paediatric Eye Disease Study Group. Prevalence of amblyopia and strabismus in African American and Hispanic children ages 6 to 72 months: The Multi-ethnic Paediatric Eye Disease Study (MEPEDS). Ophthalmology 2008;115:1229-36.  Back to cited text no. 13
    
14.
Friedman DS, Repka MX, Katz J, Giordano L, Ibironke J, Hawse P et al. Prevalence of amblyopia and strabismus in White and African American children aged 6 through 71 months: The Baltimore Paediatric Eye Disease Study (BPEDS). Ophthalmology 2009;116:2128-34.  Back to cited text no. 14
    
15.
The Joint Writing Committee for the Multiethnic Paediatric Eye Disease Study and the Baltimore Paediatric Eye Disease Study Groups. Risk factors for decreased visual acuity in preschool children: The Multi-Ethnic Pediatric Eye Disease and Baltimore Pediatric Eye Disease Studies. Ophthalmology 2011;118:2262-73.  Back to cited text no. 15
    
16.
The Joint Writing Committee for the Multiethnic Paediatric Eye Disease Study and the Baltimore Paediatric Eye Disease Study Groups. Risk factors associated with childhood strabismus: The Multi-Ethnic Pediatric Eye Disease and Baltimore Pediatric Eye Disease Studies. Ophthalmology 2011;118:2225-61.  Back to cited text no. 16
    



 
 
    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9]


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