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ORIGINAL ARTICLE
Year : 2021  |  Volume : 28  |  Issue : 1  |  Page : 23-28  

Ocular disorders among preschool children in Southwest Nigeria


1 Eleta Eye Institute, Ibadan, Oyo State, Nigeria
2 Department of Ophthalmology, University College Hospital, Ibadan, Oyo State, Nigeria

Date of Submission19-Jul-2019
Date of Acceptance07-Apr-2021
Date of Web Publication30-Apr-2021

Correspondence Address:
Dr. Olubusayo O Adejumo
Eleta Eye Institute, Ibadan, Oyo State
Nigeria
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/meajo.MEAJO_191_19

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   Abstract 


PURPOSE: The aim of the study was to determine the prevalence and causes of ocular disorders among preschool children.
METHODS: A multi-stage random sampling technique was used to select 560 children from a total of 9944 children aged 3–5 years attending nursery schools in the study area. Demographic and other relevant data were collected from the children. They underwent full ophthalmic evaluation including anterior and posterior segment examination as well as cycloplegic autorefraction.
RESULTS: Out of the 560 children screened, 170 (30.3%) were 3 years old, 183 (32.7%) were 4 years old, while the remaining 207 (37.0%) were 5 years old. Male-to-female ratio was 1:1.1. Visual acuity was testable using Lea symbol chart in 90% of the children. Ocular disorders were found in 61 eyes of 35 children giving a prevalence of 6.3%. The most common ocular disorder among participants was refractive error (3.9%), followed by allergic conjunctivitis (1.3%). Other identified ocular disorders were strabismus (0.9%), congenital cataract (0.4%), congenital ptosis (0.4%), optic atrophy (0.4%), ectopia lentis (0.2%), and phthisis bulbi (0.2%). There was no statistically significant difference in the distribution of ocular disorders by age or gender.
CONCLUSION: Screening is useful in early detection and treatment of ocular disorders in preschool children. Uncorrected refractive error which was identified as the major ocular disorder in these children is treatable. Periodic preschool vision screening would reduce the burden of uncorrected refractive error and other ocular disorders which can interfere with the learning skills of young children entering school.

Keywords: Nigeria, ocular disorder, preschool children, vision screening


How to cite this article:
Adejumo OO, Olusanya BA, Ajayi BG. Ocular disorders among preschool children in Southwest Nigeria. Middle East Afr J Ophthalmol 2021;28:23-8

How to cite this URL:
Adejumo OO, Olusanya BA, Ajayi BG. Ocular disorders among preschool children in Southwest Nigeria. Middle East Afr J Ophthalmol [serial online] 2021 [cited 2021 Sep 25];28:23-8. Available from: http://www.meajo.org/text.asp?2021/28/1/23/315316




   Introduction Top


Children's visual wellbeing is one of the top priorities of “Vision 2020: the right to sight.”[1] This is because a child's quality of life and neurological development are highly dependent on adequate vision. A visually impaired or blind child potentially has a lifetime of blindness to contend with. In addition, blindness impacts negatively on a child's education, future employment, and social welfare. A visually impaired or blind child is a burden to the family and community as a whole. With compromised vision, there are serious implications on a child's overall progress, hence the need for early vision screening in children.[2]

The preschool age generally refers to the period before primary school education, particularly the age of 3–5 years.[3],[4] Preschool ocular health is an important aspect of child health and an integral part of medical care for children.[5] Preschool vision screening offers a unique opportunity to promote the eye health of children as well as their educational experience. It has been described as an efficient and cost-effective method for early detection of visual impairment or ocular disorders that are likely to lead to vision loss.[6],[7] Preschool vision screening has been recommended by the U. S preventive services task force,[8] in all children before they enter primary school. The Preferred Practice Pattern of American Academy of Ophthalmology,[9] also recommends early eye screening, especially for age 3–5 years and at regular intervals to allow early detection of ocular disorders and prompt treatment before the young child enters school.

Hospital-based studies have been carried out in Nigeria on children of all age groups.[10],[11],[12] Visual screening programs on school age children have also been reported in Nigeria.[13],[14],[15],[16],[17],[18],[19],[20] However, there is very little information on visual screening of preschool children in Nigeria,[21] or any of the African countries. This could be due to the challenging nature of visual acuity (VA) assessment in children within the preschool age group because their attention span is very short. Nevertheless, there is a need for preschool visual assessment in order to identify children with ocular disorders before primary school entry so that they may benefit from early intervention to correct or improve vision.

This study aims to determine the ocular disorders seen among preschool children in Ijebu North local government area (LGA) in order to provide opportunity for early intervention and prevention of permanent vision loss. It would also serve as a pilot study into the logistics for introducing preschool eye screening in Nigeria.


   Methods Top


It was a community-based descriptive, cross-sectional study. A multi-stage random sampling technique was used to select 560 children from a total of 9944 children within ages 3–5 years attending both government and private nursery schools in Ijebu North LGA. Ethical approval was obtained from the Health Research Ethics Committee of Catholic Group of Hospitals, Ibadan, Oyo State, Nigeria, and a written approval was obtained from Ministry of Education, Ogun State, Nigeria. All the selected children met the inclusion criteria, their parents, or guardians consented to the study and had their demographic and other relevant data collected. They all underwent full ophthalmic assessment.

Assessment of monocular VA with Lea symbols chart began with a pretest during which the child was shown large, individual symbols at a distance of about 1 m. If the child could name the symbols or match them on a lap card, the child was asked to identify the symbols on the top line (6/60 equivalent) of the eye chart, at a distance of 3 m.

Presenting visual acuity (PVA) was recorded, for each eye, as the symbol size of the smallest line at which the child could correctly identify three of the 4 symbols. Children with VA worse than 6/18 were screened a second time after waiting for about 15 min to allow the child's attention to be regained. Children whose VA was still worse than 6/18 were screened a third time. The VA after the third screening was recorded for such children. Stereopsis was measured in normal daylight conditions for all the children using the Lang stereo test. The children were asked to name the images or point at the location of the images one by one and their response was noted. The normal range of stereopsis using this test is 550–1200 s of arc.

Hirschberg test was performed at near, by asking the child to focus on the nose of the examiner and at far by asking the child to focus on a toy held at 3 m in order to detect ocular deviation and estimate the magnitude of deviation. Cover testing using an occluder was performed on those children who had asymmetrical cornea light reflexes to confirm the direction of deviation.

The anterior segments of the children were examined using a pen torch. Their pupils were dilated with 1% cyclopentolate drops instilled at 15 min interval over 45 min. Thereafter, cycloplegic autorefraction, using handheld Welch Allyn Auto refractor, 901029 vision screener was performed to determine the children's objective refractive error. The children's posterior segments were then examined using a binocular indirect ophthalmoscope.

The children with identifiable ocular disorders were administered appropriate treatment at subsidized rates. This comprised eye drops or spectacle prescription, as necessary.

Statistical analysis

Data was entered into a computer spread sheet and statistical analysis performed using Statistical Package for Social Sciences Version 20 (IBM Corporation, New York, USA). Chi-square test was used to determine the statistical significance of any observed relationships between categorical variables and P value below 0.05 was considered statistically significant.


   Results Top


Out of the 560 children screened, 170 (30.3%) were 3 years old, 183 (32.7%) were 4 years old while the remaining 207 (37.0%) were 5 years old. The mean age of the children was 4.14 ± 0.71 years. The male-to-female ratio was 1:1.1; there were 265 (47.3%) males and 295 (52.7%) females [Figure 1].
Figure 1: Age and gender distribution of children

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PVA of 6/18 or better was recorded in the better eye of 93.2% of 5-year-old children, whereas only 67.1% of the 3-year-old children tested had PVA of 6/18 or better in their better eye. Overall, PVA of worse than 6/18 was observed in 62 (11.1%) participants [Table 1], but only 9 (1.6%) of these were aged 5 years. Level of cooperation with VA testing also improved with age; 19.4% of 3-year-old children were untestable as against 2.4% of 5-year-old children that were untestable. This difference was statistically significant [Table 2].
Table 1: Presenting visual acuity in better eye of the children (n=560)

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Table 2: Presenting visual acuity in better eye by age of participants

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VA of better than 6/18 was seen in 79.2% and 78.7% of male and female participants, respectively. There was no statistically significant difference in the VA in the better eye of male versus female subjects.

Thirty-five children (6.3%) out of the 560 participants had ocular disorders in one or both eyes; representing 61 eyes (5.4%) out of the 1120 eyes examined. Ninety-six ocular disorders were identified in these 61 eyes because some of these eyes had multiple pathologies.

[Table 3] highlights the identified ocular disorders among participants. The most common identified ocular disorder was refractive error, followed by allergic conjunctivitis. Other identified ocular disorders were strabismus, congenital cataract, congenital ptosis, optic atrophy, ectopic lentis, and phthisis bulbi.
Table 3: Identified ocular disorders among participants (n=560)

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A child with vernal keratoconjunctivitis was noticed to have a left blind eye from cornea opacity, presumed to be as a result of complication from the vernal conjunctivitis. Four of the children had esotropia, while a child had exotropia. The two children with posterior segment disorder had optic atrophy, one child had bilateral optic atrophy, while the other had unilateral optic atrophy. PVA of worse than 6/18 was seen in the better eye of 8 (22.9%) of the 35 children with ocular disorders, 23 (65.7%) had better than or equal to 6/18 vision in the better eye, while the remaining 4 (11.4%) were not cooperative with the symbol chart used to assess VA. A 5-year-old, male child was found to be blind from bilateral optic atrophy.

Ocular disorders were identified in 6.8% and 5.8% of male and female participants, respectively. Ocular disorders were identified in 6.5% of 3-year-old participants, 7.1% of 4-year-old participants, and 5.3% of 5-year-old participants, respectively. There was no statistically significant difference in the distribution of ocular disorders across the age groups as well as between male and female participants [Table 4].
Table 4: Occurrence of ocular disorder by age and gender

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Simple myopia was the most common type of refractive error accounting for 50% [Figure 2] of the identified refractive errors. Almost all the cases of myopia were in the range of −0.50 DS to <−3.00 DS (90.9%) with a mean of −2.00 ± 0.16 DS. Simple hyperopia was the least common type of refractive error (13.6%), and all cases of hyperopia were in the range of +3.00 DS to <+6.00 DS (100%) with a mean of +3.25 ± 0.15 DS. Astigmatism (myopic, hyperopic, and mixed types) accounted for 36.4% of the refractive errors with a range of −1.00 DC to −3.75 DC and a mean of –2.50 ± 0.12 DC. None of the children with refractive error had spectacle correction before examination.
Figure 2: Distribution of identified refractive error among 22 participants

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Good stereopsis was observed in 92.5% of participants. Twenty (3.6%) had stereopsis of 600 s of arc, while 15 (2.7%) had 1200 s of arc. Seven (1.2%) out of the participants had no stereopsis, four out of the children with no stereopsis had strabismus, one had bilateral optic atrophy, while the remaining 2 children had no identifiable ocular disorder.


   Discussion Top


Majority of the participants were testable with Lea symbol chart. This is in concordance with a similar study by Obajolowo,[21] Nigeria; as well as the study by Friedman et al.,[22] Maryland, USA. Hered and Murphy,[23] in their study, found better testability with Lea symbol chart compared with HOTV chart among 3 years old. This could be as a result of the fact that the symbols in the Lea chart are universal so that children would usually respond more readily compared to the HOTV chart. However, in a similar study, Adhikari et al.,[5] in Nepal reported 100% VA testability among participants. Their finding could possibly be due to the usage of two different VA test charts in accordance with the children's cooperation and possibly because some of the participants already had a previous history of ocular examination further enhancing their cooperation.

In this study, VA performance improved with age but was not associated with gender. This is akin to findings of local studies by Obajolowo as well as Osaiyuwu and Atuanya in Nigeria.[21],[24] Hered and Murphy,[23] in Florida, USA, also reported that VA performance improved with age. This association could be attributed to better cooperation, longer attention span, and a higher level of visual development with age.

This study demonstrates a higher preponderance of children with poor PVA compared with other similar studies.[5],[22],[25] This could be attributed to first time exposure to ocular checkup by the participants because as at the time of examination none of them had undergone previous eye examination.

The prevalence of ocular disorder found in this study was 6.3%. This finding is similar to those reported from similar studies on ocular disorders among preschool children in developing countries[21],[25],[26],[27] and developed countries.[28],[29],[30],[31] Obajolowo,[21] Nigeria, in a local study on preschool children, also reported prevalence close to what was found in this study. However, other local studies on school-aged Nigerian children reported higher range of prevalence of ocular disorders, this could be as a result of the fact that older age groups were studied.[13],[20],[32]

There are little or no variations in the prevalence of visual impairment among preschool children in different regions of the world. In the developing world, the prevalence of visual impairment was between 4.5% and 5.46%,[21],[25],[26],[27] while in the developed world prevalence was between 4.3% and 6.4%,[28],[29],[30],[31] except for the study at New South Wales, Australia, with a prevalence of 8.1%.[33] This high prevalence could be directly related to the fact that the study was conducted by local health district staff, and 11.2% of the children referred by the staff had no abnormality diagnosed on further evaluation by a pediatric ophthalmologist.[33]

The most common identifiable ocular disorder in this study was uncorrected refractive error followed by allergic conjunctivitis. This is comparable to similar studies in developing world[5],[21],[25],[34],[35] and developed world,[22],[28],[29],[30],[31],[33] in which refractive error was found as the commonest ocular disorder among preschool children. This finding is also similar to those reported by local studies on Nigerian children irrespective of the studied age group.[11],[12],[13],[14],[15],[16],[17],[18],[21],[32],[36]

The most common ocular disorder in this study is treatable. Therefore, greater attention needs to be paid to the refractive needs of the preschool children in the study population and Nigeria as a whole to prevent interference with the learning skills of young children entering school and to prevent permanent visual impairment from amblyopia.[37],[38] Regular, periodical vision screening at preschool entry would assist in early detection of uncorrected refractive error. In this study, treatment was administered to children with ocular disorders at subsidized rates in terms of drugs and prescribed spectacles as necessary.

Myopia was found as the major type of uncorrected refractive error in this study followed by astigmatism which is similar to what was found by Obajolowo,[21] Nigeria, Adhikari et al.,[5] Nepal, Multi Ethnic Pediatric Eye Disease Study Group,[30] Los Angeles USA and Giordano et al.,[39] Maryland, USA.

Vernal conjunctivitis/allergic conjunctivitis which was second in occurrence after refractive error in this study also needs close attention. Severe form of ocular allergy with cornea involvement, if not managed appropriately, can lead to childhood blindness as seen in a case of left blind eye (cornea opacity) from vernal conjunctivitis in this study.

In this study, there was no statistically significant difference in the distribution of ocular disorders across the age groups (P = 0.281) as well as between male and female participants (P = 0.123). This is in support of the study by Obajolowo,[21] Nigeria. A similar study by Premsenthil et al.,[25] Malaysia also found no statistically significant difference in the distribution of ocular disorder by gender (P = 0.142). However, in another study on schoolchildren in South Western Nigeria by Ajaiyeoba et al.,[32] ocular disorders were found to be significantly more common among the female schoolchildren, this may have been due to the female preponderance in that study.

This study has a few limitations. First, the study was conducted in the nursery school environment and may not provide a true picture of the ocular disorders among preschool children in the community because it is possible that some of them may not attend nursery school. Notwithstanding, this study provides useful information about the prevalence and causes of ocular disorders among preschool children while avoiding the difficult logistics of conducting a similar study at household level within the community.

Another limitation is that, maximum cooperation from the children in the course of examination was difficult to obtain because of the age of the subjects in this study. This may have resulted in under diagnosis of some ocular disorders.


   Conclusion Top


This study has shown that preschool screening with basic ocular examination is feasible in our environment and can help in early detection of ocular disorders, especially the amblyogenic risk factors such as uncorrected refractive error which was the most common identified ocular disorder in this study. Greater attention needs to be paid to the refractive needs of these children to prevent interference with their learning skills and also to prevent permanent blindness from amblyopia.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

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    Tables

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



 

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