Amblyopia is an ocular disorder with a deficiency of form or spatial vision sense resulting in the reduced visual acuity of greater than two lines between the eyes or an absolute reduction in visual acuity less than 6/9 either eye in Snellen's Vision Chart. This disorder is not correctable by refraction and cannot be attributed to any structural abnormality as well as central visual pathway defects.¹

The Global Amblyopia prevalence varies greatly across various regions due to age groups studied, racial differences, cultural differences, literacy rate, geographical factors and frequency of visual screening programs.² Literature reveals Amblyopia prevalence from as low as 0.7% to as high as 5-7%, the reasons being characteristics of study population, visual acuity criteria and measurement methods. Amblyopia remains quite a common ocular condition diagnosed in Pediatric population. Early management can lead to significant improvement in Amblyopia. Amblyopia develops due to defective development of the visual axis in Pediatric age. Continuous, clear and focused visual impulses are required by visual cortex to develop normally. Children with Amblyopia predisposing factors, if not diagnosed and treated early, are vulnerable to Amblyopia as well as blindness.³

It is observed that age of Amblyopia development is Pediatric age from early childhood to the age of 7 to 8 years. Amblyopia can be effectively treated if diagnosed and managed before the age of 9 to 10 years. Left untreated, Amblyopia can lead to permanent lifelong visual impairment.⁴

Although significant research has been done for school-going Pediatric population, but there is a lack of consensus upon the ideal age and frequency of visual screening. In United States, a mandatory vision screening is recommended for children between 3-5 years of age by the US Preventive Services Task Force. Whereas, the European countries start vision screening as early as 3-4 years of age.⁵

Cross-sectional Descriptive Study and total 6043 students had refractive error and were referred to our hospital for diagnosis of Amblyopia. The study was conducted in children of Abbottabad. Pakistan from 30th March, 2019 to 30th June, 2021. After taking permission from hospital ethics committee, a community based study was carried out after informed consent. Out of a total of 155,776 children, 6043 children (03.87%) were diagnosed having uncorrected refractive errors with Snellen chart and auto-refractokeratometer. These children went through complete retinoscopy by an optometrist in Abbottabad Ayub Teaching Hospital. Then the patients who had 6/12 vision in any eye with best possible correction whose vision is not even improved by pinhole were selected for the study. The children with squint, prior eye surgery and other ocular diseases were excluded. All the observations along with demographic information of patients were noted on a pre-designed Proforma. Data was analyzed by using SPSS version 21.

Out of these 6043 children with different refractive errors, Amblyopia was diagnosed in 118 out of 6043 children, using a visual criterion of 20/30 or less on Snellen charts  (Table-I).

Table- I: Percentage of amblyopia in various age groups

The Amblyopia prevalence was 01.95% (95% confidence interval) with significant variation (p<0.001) across various age groups. There were 54(45.76%) males and 64(54.23%) were females (Table-II)). Age distribution revealed that maximum cases of Amblyopia were seen in 13-16 years age group 59(50.0%), followed by 9-12 years age group 54(45.76%) and 5(4.23%) in 5-8 years age group (Table- III).

Table- II: Percentage of amblyopia in both genders

Table- III: Percentage of amblyopia in various age groups among both genders

Out of total 155,776 children, 6043 children (03.87%) were diagnosed having refractive errors. These results are comparable with a study done by Kalikivayi et al. who reported 3.1% undiagnosed refractive errors.⁶ The results of our study are much lower as compared to Padhye AS et al. whose cluster-weighted prevalence of uncorrected refractive error in urban and rural children was 5.46% (95% CI, 5.44-5.48) and 2.63% (95% CI, 2.62-2.64) respectively.⁷ The prevalence of Amblyopia in our study was 01.95% (95% confidence interval:0.64%-0.83%) with significant variation (p<0.001) across age groups. This is comparable to a study done in Northern Mexico where prevalence of Amblyopia was found to be 2.5%., Gupta et al. who showed a prevalence of 1.39% of participants and 1.1% by Jarwal et al.³,⁸,⁹ This Prevalence is higher as compared to 0.41% depicted by Singh et al. and 0.74% (95% confidence interval, 0.64-0.83) shown by Xiao O et al.¹⁰,¹¹ However, there are certain studies which have shown a higher prevalence of Amblyopia including 12.9% in Nigeria, 5.97% shown by Karki, 8.6% by Gupta et al and 7.53% in Malaysia.⁵,¹,²,⁵,¹² This may be attributed to ethnic variation in Amblyopia prevalence. Amblyopia was more prevalent in females in our study i.e. 54.23% as compared to 45.76% males. Similar results with female pre dominance was observed in Iran and Minia County.¹³,¹⁴ This is in contrast to Karki et al who showed Amblyopia more in males 57.14% as compared to and 42.86% females¹ and Gupta et al Male 66.66% was more amblyopic than female 33.33%.³ In 2 studies, Amblyopia had no association with age or gender.⁴,⁹ Age distribution revealed that maximum cases of Amblyopia were seen in 13-16 years age group (50.0%), followed by 9-12 years age group (45.76%) and (4.23%) in 5-8 years age group. These results are comparable with another study in which the mean age was 11 (±3.16) years.³ Similarly in another study by Cherian et al Amblyopia was commonly observed in Pediatric Population between the group of 11 - 13 years.¹⁵ In contrast a younger age was shown by Gupta M where, 51.61% cases presented between 5-10 years² and Malaysian study showed a mean age of 5.03 years (SD:0.77).⁵

Significant prevalence of amblyopia in school going pediatric population with refractive errors show inadequacy of present school screening programs in KPK, Pakistan. Initiation and regular implementation of such programs in pediatric population will lead to early detection as well as management of amblyopia.

Disclaimer:
Nothing to declare.

Acknowledgement:
The author thank the department medical staffs for their help and support. They keep patient record properly and managed the data carefully which helped in completing this research

Authors’ CONTRIBUTION:

¹Conceptualized the study and contributed in the data collection and aided in drafting of the article, ²Data collection, drafting of the article, ³Active Participation in active methodology.

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