European Journal of Cardiovascular Medicine

Amblyopia, or "lazy eye," is defined as unilateral or bilateral reduction in BCVA (Best Corrected Visual Acuity) caused by form vision deprivation or abnormal binocular interaction, without any identifiable ocular pathology.^[1,2] The American Academy of Ophthalmology describes it as an interocular difference of two or more lines in visual acuity or BCVA ≤ 20/30 with optimal correction.^[3]

Amblyopia is a common childhood visual disorder, with a global prevalence ranging from 1.6% to 3.6%.^[4] In India, prevalence rates vary: 1.1% in Southern India and 1.75% in Northern India among school-aged children.^[5,6] Underdiagnosis is common due to limited parental awareness and delayed referrals.^[7–9] Variability in reported prevalence may stem from regional, methodological, and diagnostic differences.

Risk factors include high refractive errors, strabismus, media opacities, low birth weight, maternal substance abuse, and lower socioeconomic and educational backgrounds.^[10]

Early detection and intervention are crucial, as visual pathways remain responsive to treatment during the critical developmental period. Occlusion therapy is the standard treatment, with alternatives like atropine penalization, filters, or dichoptic training. The critical window for effective treatment extends up to 17 years of age, beyond which recovery becomes limited (PEDIG).

This study aims to assess the prevalence and causes of amblyopia in children under 18 presenting to a tertiary care eye OPD in Bhopal.

Aims and Objectives

The aim of this study was to investigate the prevalence and characteristics of amblyopia in school-going children under 18 years of age presenting to the ophthalmology outpatient department of a tertiary care hospital in Bhopal. The objectives include determining the magnitude of amblyopia within this age group, identifying the contributing risk factors such as refractive errors and strabismus, and classifying the different types of amblyopia observed among the affected children. This comprehensive approach seeks to enhance early detection, improve management strategies, and reduce the long-term visual and developmental impact of amblyopia in the pediatric population.

This analytical cross-sectional study was conducted in the Department of Ophthalmology at Peoples College of Medical Science and Research Center, Bhopal, Madhya Pradesh. The study aimed to assess the prevalence and characteristics of amblyopia in school-going children under 18 years of age presenting to the eye outpatient department. Ethical clearance was obtained from the Institutional Ethical Committee prior to the initiation of the study. Detailed demographic and clinical data, including age, gender, education, and visual acuity parameters such as squint, were recorded using a structured proforma.

Inclusion and Exclusion Criteria

The study included all patients below 18 years of age presenting to the ophthalmology outpatient department at Peoples College of Medical Science and Research Center, Bhopal. Patients were excluded if they had a known cause of reduced visual acuity, a history of prior intraocular surgery, any existing pathological ocular conditions, or if they did not provide consent to participate in the study.

A total of 1000 children under the age of 18 were randomly selected for inclusion in the study. The sample comprised patients who presented to the ophthalmology OPD during the study period and met the inclusion criteria. All participants were screened for amblyopia using standardized ophthalmic evaluation protocols. The sample size was determined to be adequate for estimating the prevalence of amblyopia with reasonable precision within the target population, considering the expected prevalence from previous studies and ensuring representative coverage of school-aged children in the region.

Data Collection Tools

The tools and instruments used for data collection in this study included a vision chart (Snellen chart), streak retinoscope, autorefractometer, slit lamp (Haag-Streit 900 using Appasamy technique), Worth's four-dot test apparatus, indirect ophthalmoscope, cover test tools, prism bar, and synoptophore. These tools were employed to assess various ocular parameters such as visual acuity, refractive errors, strabismus, binocular vision, anterior segment condition, and retinal health. A structured questionnaire comprising 10 questions was also utilized, available in both Hindi and English, to capture patient history and relevant demographic information.

Data Collection Procedure

A total of 1000 children under 18 years of age presenting at the ophthalmology OPD were randomly recruited over a 16-month period following ethical approval and informed consent. A detailed history was recorded for each participant, including demographic data, educational background, and medical history. General and ocular examinations were conducted systematically for both eyes.

Visual acuity was first assessed unaided and with a pinhole, followed by objective refraction using an autorefractometer and confirmation with streak retinoscopy. Additional assessments included the Hirshberg test for strabismus, Worth’s four-dot test for binocular vision, and prism bar measurements for angle of deviation. Anterior segment evaluation was done using a slit lamp, and fundus examination was carried out using both direct and indirect ophthalmoscopes. Children with subnormal pinhole vision underwent further refraction, and those with BCVA less than 6/6 were diagnosed and categorized based on amblyopia type. Data were recorded, compiled into a master Excel sheet, and analyzed using SPSS software.

Statistical Analysis

The collected data were first entered into a Microsoft Excel spreadsheet for organization and preliminary review. Subsequently, the compiled data were analyzed using the Statistical Package for the Social Sciences (SPSS) software, version 22. Descriptive and inferential statistical methods were applied as appropriate. A p-value of less than 0.005 was considered statistically significant, indicating a high level of confidence in the observed associations and outcomes.

Table 1 presents the age and gender distribution of the 1000 study participants. The sample is evenly spread across age groups from 5 to under 18 years, ensuring a balanced representation for age-wise analysis. Gender distribution is nearly equal, with a slight predominance of females (50.7%), which eliminates gender-related sampling bias and strengthens the generalizability of the findings.

Table 2 compares the distribution of refractive errors in the overall study population and specifically within the amblyopic subgroup. Emmetropia was the most common finding overall, while hypermetropia was the predominant refractive error in amblyopic patients. The table illustrates that refractive errors are strongly associated with amblyopia, particularly hypermetropia and myopia.

Table 3 classifies refractive errors into low, moderate, and high grades for myopia, hypermetropia, and astigmatism and compares their prevalence in amblyopic and non-amblyopic subjects. Most amblyopic patients had moderate to high degrees of refractive error, especially significant hypermetropia and high astigmatism. This highlights the importance of early detection and correction of higher refractive errors to prevent amblyopia.

Table 4 details the different types, laterality (unilateral vs. bilateral), and severity of amblyopia based on BCVA. Anisometropic amblyopia was the most prevalent (50%), and most cases were unilateral (63.6%) and severe (63.6%). These findings emphasize that significant refractive imbalances between the eyes contribute most to amblyopia and that many patients present at a late stage, underlining the need for routine vision screening.

Table 5 shows that amblyopia was slightly more prevalent in males (63.6%) compared to females (36.4%). While the sample size is small, this may indicate a slight gender disparity in either the occurrence or detection of amblyopia, though more robust data would be needed to draw firm conclusions.

Table 6 compares the presence of symptoms among all patients versus those diagnosed with amblyopia. While 42.7% of all patients reported symptoms, a much higher proportion (77.3%) of amblyopic patients were symptomatic. This suggests that symptom reporting may be a useful initial indicator for detecting amblyopia during screenings.

Table 7 categorizes the types of symptoms reported by all patients and the amblyopic subgroup. Tired eyes/strain and watering/irritation were the most common complaints, often reported together. These overlapping symptoms suggest that many children experience generalized visual discomfort, and such complaints should prompt further ophthalmologic evaluation, especially in school-aged children.

Amblyopia poses a significant public health concern due to its high prevalence among children and the risk of severe, permanent visual impairment if left untreated.^[11] The current study aimed to assess the prevalence, associated factors, and types of amblyopia in school-going children under 18 years of age attending the eye outpatient department at a tertiary care hospital in Bhopal. The overall prevalence of amblyopia was found to be 2.2%, with anisometropic amblyopia being the most common type. Most cases were unilateral and associated with severe visual impairment, highlighting the importance of early detection and regular vision screening.

Among the 1,000 participants, the age distribution was relatively balanced. The largest group was children aged 7–8 years (15.9%), and the smallest was 9–10 years (13.4%). This even distribution allowed for more accurate age-related comparisons. Literature presents varying associations between age and amblyopia prevalence. Mondal M et al. found higher prevalence in the 5–10 years age group,^[12] while Aldebasi YH reported a statistically significant higher prevalence in children aged 10–13 years compared to 6–9 years.^[13] In contrast, the BPEDS (Baltimore Pediatric Eye Disease Study) observed a slight increase in prevalence with age,^[14] and a Singaporean-Chinese study found no significant variation across age groups.^[15]

Gender distribution in the study was nearly equal: females constituted 50.7% and males 49.3%. However, other studies have shown differing results. Janti SS et al. reported a male predominance (63.79%),^[16] as did Mondal M (52.8% male)^[12] and Sapkota K et al.^[17]

Among non-amblyopic children, emmetropia (38%) was the most frequent refractive status, followed by hypermetropia (25.7%), myopia (21.4%), and astigmatism (12.7%). These proportions remained consistent even when amblyopic cases were included. The 2.2% prevalence found in this study is lower than that reported by Mondal M et al., who found an 11.4% prevalence in a cohort of 500 children.^[12] In a study by Prajapati V et al., hypermetropia (42%) was the most common refractive error causing amblyopia, followed by myopia (19%), hypermetropic astigmatism (19%), myopic astigmatism (8%), and anisometropia (12%).^[18] These findings emphasize the importance of timely correction of refractive errors to prevent amblyopia.

This study further noted that amblyopic children tended to have significant hypermetropia (≥ +2.0D), high astigmatism (≥ +2.75D), and medium myopia (-3.0D to -6.0D), while non-amblyopic children commonly presented with low to moderate refractive errors.

Among the 22 amblyopic cases, anisometropic amblyopia was the most prevalent (50%), followed by isometropic (22.7%), meridional (13.7%), strabismic (9.1%), and sensory deprivation amblyopia (4.5%). This aligns with findings from Bamhane P et al. (53.33%),[19] Janti SS et al. (36.2%),^[16] and Jarwal et al. (29.5%).^[20] In the study by Janti SS et al., anisometropic (36.20%) and strabismic (25.86%) amblyopia were the most common, with hypermetropia (46.15%) more prevalent than myopia (25.64%) and astigmatism (18.20%).[16] In strabismic amblyopia, exotropia (53.33%) was more frequent than esotropia (40%) and hypertropia (6.66%). Prajapati V et al. and Menon et al. also reported hypermetropia as the most common refractive error associated with amblyopia.^[18,21] The high incidence of anisometropic amblyopia may be due to its often-unnoticed unilateral presentation in children.

In this study, 63.64% of amblyopic cases were unilateral and 36.36% bilateral, similar to Bamhane P et al.'s finding of 80% unilateral and 20% bilateral cases.^[19]

Severity analysis revealed that 18.2% of patients had mild amblyopia (6/12 to 6/24), 18.2% had moderate amblyopia (6/36 to 6/60), and 63.6% had severe amblyopia (>6/60). This is in contrast to Sinha S et al., who reported moderate amblyopia in 88% and severe in only 12% of cases.^[22] Bamhane et al. and Jarwal et al. also found moderate amblyopia to be the most common severity grade.^[19,20] Pai AS et al. noted that amblyopic eyes typically had moderate refractive errors and a mean visual acuity of 20/50.^[23]

Jamali P et al. reported that 3.6% of children had significantly impaired vision (6/12 or worse),^[24] while Murthy GV et al. found a 6.4% prevalence of uncorrected visual acuity of 20/40 or worse in the better eye, which dropped to 0.81% after correction.^[25] Kalikiyavi V et al. noted a 3.1% rate of visual impairment (<6/18 in the better eye), with 1.1% legally blind and 0.5% economically blind. Remarkably, 94.8% of those with initial visual impairment improved to 6/18 or better after correction.^[26]

In our cohort, hypermetropia was the most frequent refractive error among amblyopic children (45.45%), followed by myopia (31.82%) and astigmatism (22.73%). A slight male predominance was observed (63.64% male vs. 36.36% female), though the difference is not statistically significant.

Prajapati V et al. reported similar patterns, with hypermetropia being the most common error and males more frequently affected.^[18] Conversely, Hamid A et al. found no significant correlation between amblyopia and gender or age.^[27] In their study, 61.9% had hyperopia, 55.5% had anisometropia, and 55.56% had anisohyperopic amblyopia, with a greater prevalence of bilateral amblyopia.

Lastly, in the present study, 42.7% of all subjects were symptomatic. Among amblyopic patients, 77.3% reported symptoms-most commonly tired eyes or eye strain. This high rate of symptomatology underscores the multifactorial nature of visual complaints in this population.

LIMITATIONS

Despite a relatively large sample size, the study's findings may not be fully generalizable due to its single-center design, which introduces potential selection bias. Reliance on clinical assessments may also involve measurement errors and inter-observer variability. The absence of long-term follow-up limits insights into the progression and treatment outcomes of amblyopia. Additionally, the lack of detailed socioeconomic data restricts analysis of its influence on amblyopia prevalence.

In conclusion, this study highlights a 2.2% prevalence of amblyopia among school-going children under 18 in Bhopal, with anisometropic amblyopia being the most common type. Most cases were unilateral and associated with severe visual impairment, with hypermetropia as the predominant refractive error. A slight male predominance was observed. These findings emphasize the need for regular vision screening and early intervention to prevent long-term visual impairment.

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