Magnitude of Prevelance of Refractive Errors in School-age Children: A Cross-sectional Study

Aim: To determine the frequency of refractive errors in school-age children. Study Design: Cross-sectional study. Place and duration: Two Government and two Private schools of Hyderabad Sindh, screened by the institute of ophthalmology at Liaquat University of Medical and Health Sciences Jamshoro, from January 2021 to June 2021. Methodology: Schools and students were selected by stratified random method; a total of four hundred students were screened in four schools. From class one to class ten, 10 students were selected from each class. Prior written permission was obtained from parents. External ocular examination, visual acuity, pinhole test, autorefraction, and fundus examination were done and recorded on proforma along with the information regarding age, sex, family history, and parent’s education. The data was entered and analyzed by SPSS version 22. Results: In government schools 27 students out of 200 had refractive errors, myopia was present in Original Research Article Gilal et al.; JPRI, 34(25B): 14-21, 2022; Article no.JPRI.82363 15 15 (55.55%) students, hypermetropia in 7 (25.93%) students and astigmatism in 5 (18.52%) students, while in private schools 25 students had refractive errors. Myopia was present in 16 (64%) students, hypermetropia in 7 (28%) students and astigmatism in 2 (8%) students. Myopia and astigmatism were more prevalent in female sex being 8.1% and 2% respectively, while in males it was 6.4% and 1.4% cases. In this study, no significant refractive error difference was found between government and private sector schools. Conclusion: In our study, the prevalence of refractive errors was 13% (52) out of 400 students. Refractive errors are the most common and easily treatable causes of decreased vision in schoolaged children. It is recommended that visual acuity be checked prior to admission to school because refractive errors can be easily corrected with glasses. If it is treated in time, the child can be prevented from amblyopia and squint.


INTRODUCTION
Refractive error can be defined as an optical condition of the eye in which the parallel rays of light are not focused on fovea centralis when accommodation is at rest [1]. Refractive error is the commonest cause of visual impairment in world [2] and the second leading cause of treatable blindness [3]. It is reported that 2.3 billion people throughout the world have a refractive error, [4] only 1.8 billion people have access to ophthalmologists and optometrists and have affordable corrections [5], this leaves approximately 500 million people, including 1.5 million children, mostly in developing countries with an uncorrected refractive error causing either blindness or impaired vision [6].
Refractive error is not only uncorrected in a significant number of people, but also it has been estimated that it may remain under corrected in 50% of cases [7]. Possible risk factors for myopia are family history, level of education, intelligence, and amount of close work [8]. Some studies also indicate genetic and environmental factors [9].
The World Health Organization has launched the Global initiative vision 2020 in 1999 with the slogan "The Right to Sight" it has five priorities, they are chosen on the basis of the burden of blindness they represent. It includes Refractive errors although other major causes of blindness like Glaucoma and Diabetic retinopathy are not included [10]. Refractive errors are usually present since childhood and continue the adult life, unfortunately, they are not given much importance in our society which is evident from the fact that there is no screening system for Pre School visual examination of children either in government or in the private sector.
Effective preschool health programs are available in developed countries and refractive error detections lie mainly on school health personnel as well as the optometrist [11]. Even in the presence of such effective school health services, these developed countries are now seeking help from community health workers and teachers to detect visual disorders in schoolgoing children.
In myopia the image is focused in front of the retina, [12] this condition may result from an excess of corneal power, lens power, or both for a normal axial length or the axial length being longer than normal or longer than that which is compatible with the refractive power of the normal eye. Children usually do not complain of decreased vision. They may be unaware of their problem. They adjust to poor vision or even avoid work that requires visual concentration. Defective vision due to refractive error affects education, personality development, and career opportunities, in addition to causing an economic burden on society. The current study is planned to determine the frequency of refractive errors in school-age children as timely measures could be taken to prevent the preventable cause of blindness.

METHODOLOGY
This cross-sectional study was conducted in two government and two private schools of Hyderabad Sindh, by the institute of ophthalmology, Eye Unit-III at Liaquat University of Medical and Health Sciences Hyderabad from January 2021 to June 2021. Schools and Students were selected by stratified random method. School-going children of 6-15 years of age were included in the study. Children having corneal opacity, congenital eye diseases like glaucoma & cataract, previous ocular surgery like cataracts, glaucoma, corneal repair, history of trauma, and retinal disease like retinopathy of prematurity & retinitis pigmentosa were excluded from the study. Sample size was calculated as P = 4.27%  4%, n = 369, d = 0.02, http://www.openepi.com/SampleSize. Visual acuity of 6/6 & 6/9 was considered as normal visual acuity. Refractive errors in children were defined as uncorrected visual acuity equal to or worse than 6/12 in one or both eyes [2]. Myopia was defined as spherical equivalent equal to or worse than -0.5 DS [4] and spherical equivalent equal to or worse than -5.00 DS was classified as high myopia. Hypermetropia was defined as refractive error equal to or worse than +2.0 DS [4].
We took permission and completed a list of public sector schools in Hyderabad from the director of education and divided the schools into two groups, group one comprised government schools, and group two comprised private schools. We selected two schools from each group by stratified random method. Permission was taken from principals of all four schools. The visiting team comprised of one doctor and two technicians. Prior informed written consent was taken from parents. From class one to class ten, 10 students were selected from each class by stratified random method. All the selected students were examined for external ocular examination to exclude corneal opacity, cataract, and previous ocular trauma. Visual acuity was recorded uniocularly in both eyes; Snellen's chart was used for visual acuity. Pinhole test, autorefraction, and fundus examination were done. A subjective correction was given to Students who had visual acuity of 6/12 or poor. Refractive errors were labeled as per operational definitions. The age, sex, family history, parent's education, and refractive error were recorded on proforma. We used cyclopentolate Hydrochloride eye drop to have accurate refractive values. We also used spherical equivalents for hypermetropia and myopia or ignore astigmatic measurements.
Data was entered and analyzed on SPSS version 22. Mean with standard deviation was calculated for the age of patients. Frequencies and percentages were calculated for categorical variables like sex, visual acuity, parent`s education, and outcome variables (Hypermetropia, myopia, and Astigmatism). Pvalue ≤0.05 was taken as significant.

RESULTS
Total 400 students from 4 schools were screened out, 200 students were from government schools and 200 students were from private schools.

DISCUSSION
Refractory errors are the most common eye problems causing visual impairment in the general population. Uncorrected refractive errors in children can cause reduced visual acuity, blurring of vision, reduced reading efficiency, and school performance.
In our study, the prevalence of refractive error was 13% (52) out of 400 students. We divided students into two groups, in government schools 13.5% (27) students out of 200 had a refractive error and in private schools, 12.5% (25) students out of 200 had a refractive error. In government schools 55.55% (15) were myopic, 25.93% (7) were hypermetropic and 18.52% (5) were astigmatic while in private schools 64% (16) were myopic, 28% (7) were hypermetropic and 8% (2) were astigmatic. In this study there was no statistically significant refractive error difference was found between government and private sector schools. Similarly, myopia was present in 33.3% of cases in an international study and astigmatism in 13.4% of cases. Although they included persons up to the age of 30 years results were similar to us signifying the more prevalence of these visual problems in children as well as young adults [13]. Furthermore, in 15-20 years old adolescents, the prevalence of refractory error was 24.7%. About 10.4% of children were myopic. It signifies the less prevalence of myopia in adolescents [14]. The results of our study showed an association of refractive error with gender; Myopia and Astigmatism were more prevalent in the female sex being 8.1% and 2% respectively while in males it was 6.4% and 1.4%. Hypermetropia was more common in males being 3.9% as compared to 3% in females. An unsimilar study from Saudi Arabia showed no sex difference for refractive errors, it was present in 4.2% boys and 4.9% girls. The prevalence of refractory errors was just 4.5%. This difference may be due to racial and geographical factors [17]. Furthermore in another study females had a slightly higher refractive error (6.93%) than males (5.9 %) [18]. A local study in 2014 showed a low prevalence (3.3%) of reduced vision in school-going children but like our study majority of children (65.5%) were female [19]. Another local study conducted in 2016 showed a high prevalence (20.4%) of refractive errors in school-going children, signifying the different prevalence in various regions of Pakistan [20].

CONCLUSION
In our study, the prevalence of refractive error was 13% (52) out of 400 students. Refractive errors are the most common and easily treatable cause of decreased vision in school-aged children. It is recommended that visual acuity should be checked prior to admission to school because refractive error can be easily corrected with glasses. If it is treated in time, the can be prevented from amblyopia and squint.

PARENTAL CONSENT
Prior informed written consent was taken from parents.

ETHICAL APPROVAL
It is not applicable.