Pattern and prevalence of eye disorders and diseases in school-aged children: findings from the Nationwide School Sight Sampling Survey in Armenia

Introduction

Over 20 million children around the world are either blind or suffer from visual impairment.1 2 The prevalence and causes of visual impairment in children largely depend on the level of socioeconomic development of the country, availability and accessibility of ophthalmic care services, and behavioural patterns of the society.3 The global prevalence of blindness in children is estimated at 0.75 per 1000 children, with the highest level of 0.9 per 1000 in low-income countries compared with 0.7 in middle-income and 0.4 in high-income countries, respectively.4

Most cases of childhood visual impairment are treatable and often preventable. Worldwide, nearly 1% of all children in the age group 5–15 years are visually impaired from uncorrected or inadequately corrected refractive errors.5 6 If left untreated, visual impairment among children can have a severe negative impact on their education, personal development and future economic productivity.7 Innovative community-based strategies are required to provide quality services; periodic vision screening is imperative for detecting visual impairment and managing or preventing disease progression in children.2 As a pre-emptive measure, paediatric vision screening has shown to improve quality of life, educational outcomes, visual acuity (VA), prevention of disease and economic benefits, individually, nationally and globally.8 In particular, implementation of school-based vision screenings (SBVS) as part of school health programmes is highly recommended for low-income and middle-income countries (LMICs).7 8 Over the past two decades, more and more LMICs have implemented SBVS programmes.9

Armenia is an upper-middle-income country situated in Western Asia with a population of 2.98 million, a per capita gross domestic product of US$4732 and 26.4% poverty rate.10–12 Children are among the most vulnerable segments of the population, with nearly 34% of them living in poverty.11 There is very little information available on the prevalence of paediatric eye diseases and disorders in Armenia. The only official data available are on the incidence of ‘diseases of eye and adnexa’ (48.7 per 1000 children aged 0–14 in 2019), which are collected and reported by the National Institute of Health of Armenia in their Health and Health Care Statistical Yearbook.13 This lack of data limits the possibility of implementing targeted eye care policies to ensure quality eye care for all children in the country.

Paediatric eye care in Armenia faces two major challenges: (1) optometry as a profession does not exist in Armenia, so all eye care are directed by ophthalmologists; and (2) majority of ophthalmologists are concentrated in Yerevan, the capital, which leaves children in the rest of the country with limited access to appropriate care. There are 10.8 ophthalmologists per 10 000 children aged 0–14 years old in Yerevan, compared with an average of 1.9 in the rest of the country.13 Given that the gross enrolment of children aged 6–15 years old in public schools is high at 92%, SBVS could serve as an effective approach to increasing access to eye health services among children in Armenia.14

The Armenian EyeCare Project (AECP), a non-governmental organisation established in 1992, has been a leader in improving access to and quality of eye care services across the lifespan in Armenia.15–20 In 2018, the AECP, in collaboration with Children’s Hospital Los Angeles, launched a new paediatric vision programme with two interconnected components. The School-Based Vision Screening Initiative (SBVS-I) was intended to reduce regional disparities in eye care through provision of a full cycle of comprehensive screening, diagnostic and treatment services to schoolchildren throughout Armenia. The Nationwide School Sight Sampling Survey (NS4) was designed to collect reliable data on eye diseases and disorders among school-aged children in Armenia through the SBVS-I to develop internationally recognised indicators of their prevalence. Here we present our analysis of the NS4 along with the prevalence of eye disorders and diseases with their causes among schoolchildren in Armenia for the first time since the 1990s.

Methods

Vision screening procedures

Among children whose parents provided consent, vision screening consisted of a four-step process (figure 1).

Step 1: VA assessment

Initial screening was performed by an ophthalmologist and a nurse using a Snellen linear letter or linear picture vision chart at a distance of 6 m. Each eye was tested independently and the opposite eye occluded with a hand. VA better than 20/40 in both eyes was considered normal and no further testing was performed. VA equal to or worse than 20/40 in either or both eyes was considered abnormal. Children with an abnormal VA screen, along with those whose VA was not possible to assess, proceeded to steps 2 through 4.

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Figure 1

Screening flow diagram. IBP, instrument-based photoscreening; NS4, Nationwide School Sight Sampling Survey; SBVS-I, School-Based Vision Screening Initiative; VA, visual acuity.

Step 2: instrument-based photoscreening

Children were examined by a technical specialist using Spot Vision Screener (Welch Allyn, Skaneateles Falls, New York, USA) in a darkened room following standard manufacturer-recommended protocol.21 We used the following photoscreener settings: hyperopia (≥+2.50 D spherical equivalent (SE)), myopia (≥−1.00 D SE), astigmatism (≥+1.00 D), anisometropia (≥+1.00 D SE) and strabismus (≥8.0°).

Step 3: ophthalmologist’s examination at school

An ophthalmologist was present and examined all children with an abnormal screen using an ophthalmoscope, with the primary goal of identifying a possible disease or disorder that required immediate attention. The ophthalmologist prepared a referral for every child for a comprehensive examination at a specialised eye clinic. Parents received a follow-up letter that described why their child needs comprehensive eye examination, an instrument-based photoscreening (IBP) results printout and a voucher for a no-cost comprehensive eye examination.

Step 4: comprehensive eye examination in specialised eye clinics

All children identified with abnormal or unmeasurable VA received a voucher from the AECP for a free comprehensive eye examination within 2 months of their screening. These examinations were performed by ophthalmologists in 12 central and regional specialised eye clinics or departments, and included assessments of VA, sensorimotor examination, anterior segment evaluation, cycloplegic refraction and fundoscopic examination. The following definitions were used: low hyperopia (≤+2.25 D SE), moderate hyperopia (+2.50 D to +5.00 D SE), high hyperopia (≥+5.25 D SE), low myopia (0 to −1.50 D SE), moderate myopia (−1.75 D to −5.75 D SE), high myopia (≤−6.00 D SE), astigmatism difference between the two main meridians of the eye (≥1.00 D) and anisometropia difference of refractive power between eyes (≥+2.00 D SE).

Results

Discussion

This study represents the largest and most rigorous evaluation to date of VA among children aged 6–15 years old in Armenia since its independence in 1991. The SBVS-I successfully screened 22 600 children in every region of Armenia, from which a nationally representative NS4 cohort of 5944 children was derived. Overall, 15% of children failed the initial VA screen; 9.7% were found to have some form of visual impairment and 0.05% had blindness. The majority of children with VI had treatable refractive errors. The study revealed a statistically significant association between gender, age and geographical region and prevalence of VI. Girls, children aged 10–15 years old, and children living in Yerevan and other urban areas all had higher prevalence of VI. This urban–rural difference is consistent with other published studies.23

There are very few studies of VA among schoolchildren in Armenia. In 2000, the American University of Armenia conducted the Summer Camps Visual Impairment Project, which screened 3307 children aged 6–17 attending summer camp in three regions of Armenia, and found that 11% had refractive errors.24 A 2011 study of 112 socially vulnerable children in Yerevan reported an 18.8% prevalence of refractive errors.25 Finally, in 2017, Giloyan et al26 screened 1260 schoolchildren in Yerevan and Gegharkunik (a rural area) as part of their study to assess the prevalence of risk factors for developing myopia and found a prevalence of 18% for myopia, 3.4% for hyperopia and 3.2% for astigmatism. Similar to our research, they also reported that children living in Yerevan had more VI.

Throughout the world, VI impacts children and their families, hindering academic success, career opportunities and social life.27 Programmes to screen school-aged children in LMICs, while challenging, can be safe and effective tools to reduce the burden of VI and decrease healthcare costs, and have been implemented in several countries.1 28–30 Table 4 provides a brief summary of a sample of other SBVS studies for context.31–38 Our study is comparable with others in terms of size and scope, with VI and refractive error prevalence within the same range. It is important to note that there is significant variability across studies in protocols, diagnostic definitions and data collection, so there are limitations to the generalisability of the findings of any one study. The underlying causes of visual impairment are heterogeneous and include genetic, developmental, environmental and socioeconomic factors, further limiting how meaningful it might be to compare across countries.23

A significant strength of our initiative is the continuum-of-care approach applied to the SBVS algorithm, which ensured that all children with an abnormal screen had access to additional services, including IBP, same-day evaluation with an ophthalmologist in school and vouchers for free comprehensive eye examinations at nearby specialised eye clinics. This approach is new for Armenia and can serve as a model for government-led public health initiatives for periodic eye screenings in schools. Our experience during the COVID-19 global pandemic has helped us identify ways in which this programme could be changed to minimise personal contact by using telemedicine and telehealth, mobile apps, etc. This ‘digitization’ of SBVS could be synergistic with other initiatives in Armenia meant to provide children and their families with more health literacy resources and connect individuals to healthcare services through the internet. Other strengths of this study include its large, nationally representative sample size, robust statistical design and cross-sector collaboration with multiple stakeholders.

The sensitivity of our IBP was lower than other studies in the literature. Barugel et al39 reported that the sensitivity of the Spot Vision Screener in detecting myopia was 84.61% and for astigmatism 78.57%, while we found sensitivities of 66% and 52%, respectively. Peterseim et al40 found a sensitivity of 77.17% in detecting strabismus compared with 61% in our study.40 Other studies consistently report overall sensitivity for detecting refractive errors to be greater than 80%.39–42 One possible explanation for the lower sensitivity in our study was the IBP settings. For example, the cut-off for myopia on IBP was ≥−1.00 D (consistent with local practice in Armenia), but the comprehensive eye examination could have detected lower values. Given the differences in populations, methods and analyses, it is difficult to interpret this difference in sensitivity findings, but they may represent an opportunity to optimise our implementation of and adherence to IBP protocols.

There are certain limitations to our study. All forms, including demographic surveys, medical histories and voucher forms, were completed by hand by parents, so in some cases information was missing or illegible. Among the 403 children who had comprehensive eye examinations, complete data were only available for analysis for 365 of them, representing nearly 10% data loss. The voucher system, while innovative, also had setbacks. Only about half of all families issued a voucher actually had a comprehensive eye examination, despite being provided information about the importance of further evaluation and treatment. One reason for this is that parents would have had to travel to the nearest city or the capital to be examined, which could be a significant limitation for some families in rural regions. It is possible that some families received follow-up care with an ophthalmologist not associated with our study or organisation, although this is less likely in rural regions where the AECP may be the only provider of eye health services. Lack of parental awareness of childhood visual disorders and their consequences may have also played a role.16 Half of parents were not aware that their children had VI, according to self-reported data. This further suggests that a significant number of schoolchildren do not undergo appropriate visual examination on admission to school or periodically thereafter, despite the existence of relevant requirements.

Conclusion

Our results show that a national SBVS programme is feasible in Armenia. For the first time since the 1990s, new data are available to calculate the prevalence of VI and blindness among Armenian schoolchildren aged 6–15 years old. This study shows that the majority of visual abnormalities among this population are due to treatable refractive errors. Our findings stress the importance of regular eye examinations of schoolchildren for early detection, prevention and treatment of VI. The continuum-of-care approach can serve as a model for other screening programmes and could be easily replicated throughout Armenia. Finally, there is a need for additional public education raising awareness among parents, school staff and children about vision problems and the importance of eye health.