Prevalence of high myopia and its associated factors among secondary school students at Finote-selam town, Northwest Ethiopia, 2023

Abstract

High myopia is a severe form of myopia defined as a refractive error of –6.00 diopters or more associated with a high risk of irreversible visual impairment and blindness. However, data on its magnitude and determinants among school-aged children in Ethiopia are scarce. This school-based cross-sectional study was conducted from May 10 to June 10, 2023, among 408 secondary school students in Finote-Selam town, Northwest Ethiopia, selected using systematic random sampling. Data were collected using a pretested structured questionnaire, and refraction was assessed through dry retinoscopy followed by subjective refraction. High myopia was defined as a spherical equivalent refractive error of −6.00 diopters in either eye. Data were entered into EpiData 4.6 and analyzed using SPSS version 25. Variables with a p-value < 0.05 in the multivariable analysis were considered statistically significant. The prevalence of high myopia was 3.77% (95% CI: 1.90–5.70). Factors significantly associated with high myopia included a family history of myopia (AOR = 2.80; 95% CI: 1.46–20.02), ocular comorbidity (AOR = 5.02; 95% CI: 1.40–18.06), low outdoor activity (AOR = 3.68; 95% CI: 1.20–11.29), and prolonged near-work activity (AOR = 5.25; 95% CI: 1.13–24.46). High myopia was present among a notable proportion among secondary school students, and both genetic and behavioral factors contributed to its occurrence. Promoting outdoor activities, monitoring high-risk individuals, limiting excessive near-work, and managing ocular comorbidities are recommended to reduce the burden of high myopia.

Introduction

High myopia (HM) is a severe form of myopia defined as a refractive error of –6.00 diopters or more, typically resulting from excessive elongation of the eyeball that leads to structural changes and progressive atrophy of ocular tissues^1,2. It is both a refractive and pathological condition associated with an increased risk of irreversible vision-threatening complications such as retinal detachment, myopic macular degeneration, glaucoma, and cataract ^3–6. These complications can cause significant visual impairment and blindness, making high myopia a major global public health concern.

Beyond its clinical implications, myopia imposes a considerable socioeconomic burden through direct medical costs and indirect losses in productivity and quality of life ⁷. The risk of myopia and its complications is particularly high in East Asian populations, where myopic macular degeneration remains a leading cause of blindness ^8,9. Environmental and behavioral factors, especially prolonged near-work activities, intensive educational demands, and limited outdoor exposure, have been identified as modifiable risk factors contributing to the onset and progression of myopia¹⁰.

Globally, the prevalence of myopia and high myopia has been increasing at an alarming rate. It is estimated that by 2050, nearly half of the world’s population will be affected by myopia, with around 10% developing high myopia ¹¹. According to the World Health Organization (WHO), approximately 2.8% of the global population (about 170 million people) were affected by high myopia in 2010 ¹². Studies in Western countries report prevalence rates ranging from 1.6% to 4.6%, whereas Asian populations show higher figures, from 0.8% to 9.1% ^13,14. A systematic review and meta-analysis conducted in China reported a prevalence of 5.3%¹⁵. This growing trend is concerning because sight-threatening complications of high myopia are expected to affect more than one billion people by 2050¹¹.

Although most studies on myopia have focused on Asian and Western populations, emerging evidence shows that myopia is also becoming a significant concern in Africa. A systematic review and meta-analysis among African school children reported a pooled prevalence of 4.7% ¹⁶. In Ethiopia, a school-based study found that approximately 6.5% of participants were myopic ¹⁷. However, limited data are available specifically on high myopia, which carries the highest risk for vision loss.

It is crucial to establish preventive and control strategies against myopia, particularly high myopia, through early detection and timely intervention. A clear framework for evaluating and treating myopia involves understanding its impact. By detecting myopia early and implementing interventions to slow its progression, we can reduce the risk of sight-threatening complications, as well as the financial burdens associated with managing the condition. This proactive approach would lead to improved visual outcomes, resulting in both financial benefits and an enhanced quality of life for individuals and society as a whole ^7,18.

Therefore, this study aimed to assess the prevalence of high myopia and identify its associated factors among secondary school students in Finote Selam, Northwest Ethiopia. The findings will provide essential baseline data for developing early intervention strategies, inform school-based vision screening programs, and guide public health policies aimed at reducing the burden of myopia-related visual impairment in Ethiopia.

Methods and materials

Study design

A school-based cross-sectional study was conducted.

Study area and period

The study was conducted in Finote Selam town, located in the West Gojjam Zone of northwest Ethiopia, from May 10 to June 10, 2023. The town lies approximately 387 km northwest of Addis Ababa, the capital city of Ethiopia, and 176 km southwest of Bahir Dar, the capital of the Amhara Regional State. According to the 2007 Ethiopian Central Statistical Agency census, the town has a total population of 25,148¹⁹. In the town, there is one general hospital, one public health center, and five private clinics. The general hospital includes a primary eye care ophthalmic clinic, which consists of one room and is staffed by two ophthalmic nurses. Those ophthalmic nurses serve a population of around 1.5 million to 2 million people in the catchment area. Additionally, there is one optical workshop in the town. Administratively, Finote Selam is divided into six kebeles (the smallest administrative units). Educationally, it comprises eight elementary schools and three government secondary schools, namely Gojjam Secondary School, Damot Secondary School No. 1, and Damot Secondary School No. 2.

Source population/ Study population

All secondary school students at Finote Selam Town.

Inclusion and Exclusion Criteria

Inclusion criteria

All secondary school students at Finote Selam Town.

Exclusion criteria

Students who have an active ocular infection and inflammation, especially those who have involve intraocular structure.

Sample size determination

The sample size was calculated by a single population proportion formula

where; n – sample size.

Z – Value of z statistic at 95% confidence interval = 1.96.

The estimated proportion of high myopia was set at 50% due to the absence of previous studies conducted in Ethiopia. The margin of error was established as 5% (0.05), resulting in a required sample size of 384. Taking into account a 10% non-response rate, the final sample size needed is 424.

Sampling technique and procedure

A total of 7,706 students were enrolled across secondary schools in Finote Selam town during the study period. The required sample size was 424 students. The sample was proportionally allocated to each school based on the number of students enrolled. A systematic random sampling technique was employed to select participants from each school. The sampling interval (k) was calculated by dividing the total number of students in each school by the sample size. Accordingly: Damot Secondary School 1: k = 2833/424≈6, Damot Secondary School 2: k = 3003/424≈7 and Gojjam Secondary School: k = 1870/424≈4.

To select participants, a random starting number between 1 and the respective k value was chosen using the lottery method from each school’s student roster. Subsequently, every kth student was included until the allocated sample size for that school was achieved (Fig. 1).

Fig. 1.

A schematic representation of the sampling technique and procedure on the prevalence and associated factors of high myopia among secondary school students in Finote Selam Town, Northwest Ethiopia 2023.

Variables of the study

Dependent variable

High myopia.

Independent variable

The independent variables in this study were categorized into three domains: Sociodemographic, clinical, and environmental factors. Sociodemographic variables included age, sex, educational level, residency, family history of myopia, and family income. Clinical variables comprised ocular comorbidities and working distance during near tasks. Environmental variables encompassed outdoor activity, duration of near-work activities, average sleeping duration, and engagement in active rest during close work. These variables were assessed to identify potential factors associated with high myopia among secondary school students.

Operational definition

High myopia It is a condition in which the spherical equivalent refractive error of an eye is 6.00 D when ocular accommodation is relaxed²⁰.

Family history of myopia The presence of any degree of myopia in first-degree relatives (father, mother, brothers, and sisters) diagnosed by eye care professionals during examination ²¹.

Active rest during close work Considered as “yes” when the student takes rest commonly during reading and “no” when the student takes rest occasionally or never ²².

Outdoor activity Considered as yes if the child spent > 2 h per day in outdoor activities including playing games and sports ²¹.

Working distance The habitual distance range at which a person adapts to do near tasks and is considered as 33-60 cm. A habitual working distance shorter than 30 cm is considered a close working distance²³.

Data collection tools and procedures

Data were collected by three senior clinical optometrists using a pre-tested and structured questionnaire. The questionnaire comprised sections addressing socio-demographic characteristics, environmental factors, and clinical parameters. The data collection tool was adapted from previously published literature ^24–26. specifically, the measurement of the outcome variable was adapted from the International Myopia Institute guidelines ²⁰, while independent variables such as family history of myopia ²¹, Active rest during close work ²², outdoor activity²¹, working distance²³, family income ²⁷, Age of study participant ¹⁷, ocular comorbidity⁴ were adapted from related studies. The original English version of the questionnaire was translated into Amharic and modified to ensure clarity and ease of understanding during interviews. In addition, ocular examination checklists were used to assess near and distance visual acuity, perform objective refraction, and identify any ocular abnormalities. Participants’ habitual working distance was measured by first asking each participant to demonstrate their usual near working distance using a reading material, and that distance was then measured using a tape meter.

Comprehensive ocular examinations were conducted using standard instruments, including the Snellen visual acuity chart, pinhole occluder, retinoscope, trial case lenses, trial frame, pen torch, and direct ophthalmoscope. Unaided visual acuity was initially assessed for each participant; those with visual acuity worse than 6/12 underwent pinhole testing. Anterior segment evaluation was performed using a pen torch, ocular alignment was assessed using the cover test, and posterior segment examination was carried out with a direct ophthalmoscope.

The outcome variable, high myopia was defined as a spherical equivalent refractive error of ≥  − 6.00 diopters in either eye, determined through objective refraction using retinoscopy followed by subjective refraction to obtain the final refractive status. Finally, students diagnosed with ocular abnormalities or refractive errors, including myopia, were referred to Finote Selam General Hospital for further evaluation and management.

Data quality control

A pretest was conducted on 5%(n = 22) of the total sample size among secondary school students in Bahir Dar City. Based on the pretest findings, necessary modifications were made to the data collection tools. Additionally, the data collectors, who were trained optometrists, received comprehensive training before data collection. Moreover, the principal investigator and the supervisor closely monitored the daily data collection process to ensure completeness, accuracy, and consistency of the information gathered during fieldwork. In addition internal consistency of the questionnaire was assessed using Cronbach’s alpha with value of 0.85.

Data processing and analysis

The collected data were coded and entered into EpiData version 4.6 and subsequently exported to SPSS version 25 for analysis. The investigator conducted all analyses using the same software. Descriptive statistics, including proportions, means, and standard deviations, were computed to summarize the data.

The wealth index was used to assess the household socioeconomic status and was constructed using Principal Component Analysis. Variables with a prevalence of less than 5% or greater than 95% were excluded from the PCA. Components with eigenvalues greater than 1 were retained for extraction, and varimax (orthogonal) rotation was applied to improve interpretability. The resulting wealth scores were categorized into three groups poor, middle, and rich and subsequently divided into wealth quintiles.

Binary logistic regression analysis was employed to identify factors associated with the outcome variable. Variables with a p-value < 0.2 in the bivariate analysis were included in the multivariable logistic regression model. The strength of the association was determined using Adjusted Odds Ratios (AOR) with 95% Confidence Intervals, and a p-value < 0.05 was considered statistically significant. Multicollinearity among independent variables was assessed using the Variance Inflation Factor and tolerance values indicating acceptable levels. The model fitness was checked using the Hosmer–Lemeshow goodness-of-fit test, which indicated that the model adequately fit the data.

Ethical consideration

Ethical approval for this study was obtained from the Ethical Review Committee of the College of Medicine and Health Sciences, University of Gondar. Permission to conduct the research was secured through formal letters addressed to the Amhara Regional Institute of Public Health, the Finote Selam Town Zonal Health Office, the Finote Selam Administrative Education Office, and the selected schools.

Written informed consent was obtained from the parents or legal guardians of all participants younger than 18 years, together with assent from the students themselves. Participants aged 18 years and above provided their own written informed consent.

All participants were fully informed about the study objectives, their voluntary participation, and their right to withdraw at any time without penalty. Confidentiality was maintained by assigning code numbers and excluding personal identifiers from all records. Students identified with myopia or other ocular conditions were referred to Finote Selam General Hospital for a comprehensive ocular examination and appropriate management. All study procedures adhered to the Declaration of Helsinki.

Result

Socio-demographic characteristics of study participants

A total of 408 students participated in the study, yielding a response rate of 95.9%. Of these, 207 (50.7%) were female. The mean age of participants was 17.49 ± 2.02 years, ranging from 13 to 25 years. More than half of the participants, 231 (57.1%), were urban residents. Regarding family economic status, 199 (48.8%) reported having a low income. Most participants, 247 (59.9%), were aged between 13 and 16 years. With respect to educational level, the largest proportion of students were in grade 12, comprising 118 (28.3%) of the sample (Table 1).

Table 1.

Socio-demographic characteristics of secondary school students enrolled in the study at Finote Selam Town, Northwest Ethiopia, 2023 (n = 424).

Variabe	Frequency	Percent
Age
13–16	247	59.90
17–25	161	40.10
Sex
Male	201	49.30
Female	207	50.70
Residency
Rural	177	42.90
Urban	231	57.10
Family income
Low income	199	48.80
Middle income	91	22.40
High income	118	28.80
Educational level
Grade 9	95	23.80
Grade 10	96	23.60
Grade 11	99	24.30
Grade 12	118	28.30

Clinical characteristics of study participants

Among the 408 study participants, the majority, 347 (84.2%), had no ocular comorbidities, and 336 (81.6%) reported no family history of myopia. Additionally, 184 (45.8%) of the participants had a habitual reading distance of less than 33 cm (Table 2).

Table 2.

Clinical characteristics of secondary school students enrolled in the study at Finote Selam Town, Northwest Ethiopia, 2023 (n = 424).

Variable	Frequency	percent
Ocular comorbidity
Yes	61	15.80
No	347	84.20
Habitual working distance
< 33 cm	184	45.80
33–60 cm	144	35.60
> 60 cm	76	18.60
Family history of myopia
Yes	72	18.40
No	336	81.60

Environmental characteristics

In this study, the majority of students, 336 (81.1%), reported engaging in more than 2 h of outdoor activity per day. Approximately 155 participants (37.5%) had sleep duration of more than 10 h per night, while around 162 (39.2%) engaged in less than 3 h of near-work activity daily. Most participants, 336 (71.0%), reported taking active breaks during close work (Table 3).

Table 3.

Environmental characteristics of the study subjects at Finote Selam Town, Northwest Ethiopia, 2023 (n = 424).

Variable	Frequency	Percent
Outdoor activity
< 2 h	72	18.90
> 2 h	336	81.10
Near work activity
< 3 h	162	39.20
3–6 h	94	22.60
7–9 h	76	18.40
> 9 h	76	19.80
Sleep duration
< 8 h	133	33.30
8-10 h	120	29.20
> 10 h	155	37.50
Active rest during close work
Yes	336	71.00
No	72	29.00

Prevalence of high myopia

The overall prevalence of high myopia among secondary school students in Finote Selam town was 3.77% (95% CI: 1.90–5.70) (Fig. 2).

Fig. 2.

Prevalence of high myopia among secondary school students at Finote Selam Town, Northwest Ethiopia, 2023 (n = 424).

Factors associated with high myopia

In the bivariable analysis, age, family history of myopia, ocular comorbidities, near-work activity, outdoor activity, and active rest during close work showed a p-value of less than 0.20 and were therefore included in the multivariable analysis.

After adjusting for potential confounders in the multivariable analysis, four factors were independently associated with higher odds of high myopia. Students with a family history of myopia had approximately 2.8 times higher odds of developing high myopia compared with those without such a history (AOR 2.80; 95% CI: 1.46–20.02). The presence of ocular comorbidities was associated with a fivefold increase in the odds of high myopia (AOR 5.02; 95% CI: 1.40–18.06) compared with students without ocular comorbidities. Engaging in less than 2 h of outdoor activity per day was linked to higher odds of high myopia (AOR 3.68; 95% CI: 1.20–11.29) relative to 2 h or more of outdoor activity. Similarly, near-work activity of less than 3 h per day was associated with higher odds of high myopia (AOR 5.25; 95% CI: 1.13–24.46) compared with 3 h or more of near work (Table 4).

Table 4.

Factors associated with high myopia in bivariate analysis and multivariate analysis among study participants at Finote Selam Town, Northwest Ethiopia, 2023 (n = 424).

Variable	High myopia		COR (95%CI)	AOR (95%CI)	P-Value
	Yes	No
Age
13–16	7	247	1.00	1.00
17–25	9	161	1.97 (0.72–5.40)	1.25 (0.36–4.37)	0.72
Family history of myopia
Yes	6	72	1.00	1.00
NO	10	336	2.80 (1.27–7.95)	5.40 (1.46–20.02)	0.012
Ocular comorbidity
Yes	6	61	1.00	1.00
NO	10	347	3.41 (1.20–9.74)	5.02 (1.40–18.06)	0.014
Outdoor activity
< 2 h	7	72	4.67 (1.70–12.85)	3.68 (1.20–11.29)	0.023
> 2 h	9	336	1.00	1.00
Naar work activity
< 3 h	4	162	1.00	100
3–6 h	2	94	0.86 (0.16–4.80)	1.02 (0.15–7.11)	0.98
7–9 h	2	76	1.07 (0.19–5.95)	0.95 (0.15–6.17)	0.96
> 9 h	8	76	4.26 (1.25–14.60)	5.25 (1.13–24.46)	0.035
Sleep duration
< 6 h	8	133	2.33 (0.69–7.91)	4.72 (0.96–23.24)	0.06
7.01 h-8 h	4	120	2.34 (0.42–13.07)	2.31 (0.47–11.35)	0.30
> 8 h	4	155	1.00	1.00
Active rest during close work
Yes	9	292	1.96 (0.71–5.38)	2.63 (0.75–9.25)	0.13
No	7	116	1.00	1.00

Discussion

This study assessed the prevalence of high myopia among secondary school students in Finote Selam town, Northwest Ethiopia. The findings revealed that high myopia was relatively prevalent in this population, with 3.77% of the students affected. This prevalence is comparable to findings reported in Finland (3.9%)²⁶, Shanghai (4.2%)²⁸, and China (3.2%)²⁹. Similarly, the result is consistent with a study conducted in the USA, Europe, and Australia, which reported a high myopia prevalence of approximately (4.6%)³⁰. This similarity may be due to comparable educational demands, near work activities, and limited outdoor exposure among students, which are known risk factors for myopia development. Genetic and environmental influences may also contribute to the comparable prevalence rates observed across these populations.

However, the prevalence observed in this study is relatively low compared to findings from population-based studies conducted elsewhere ^31–34. It is also lower than the prevalence reported in studies from China(19.5%)and Taiwan(10.9%) ^35,36. These discrepancies across studies may be attributed to differences in genetic susceptibility, environmental factors, socioeconomic conditions, educational pressure, and methodological variations, including differences in measurement techniques and diagnostic criteria. In contrast, the prevalence reported in this study is higher than that found in studies conducted in Israel(1.7%)⁶ and Greater Beijing(1.5%)²². This variation may be attributed to differences in diagnostic criteria, such as the threshold diopters used to define high myopia, the use or absence of cycloplegia during refraction, differences in sampling frames (school-based versus clinic-based studies), and variations in the period of data collection, all of which can substantially influence the reported prevalence rates.

In terms of associated factors, students with a family history of myopia had higher odds of developing high myopia. This finding is consistent with studies conducted in the United Kingdom ^26,37. The possible explanation for this association is that a family history of myopia represents a strong genetic predisposition influencing ocular growth and structure. Children with myopic parents, particularly when both parents are myopic are at a substantially higher risk of developing myopia and progressing to high myopia. This risk is even greater if the parents themselves have high myopia. Moreover, children with highly myopic parents tend to develop myopia at an earlier age and experience faster progression, especially due to accelerated axial length elongation, which is a key determinant in the development of high myopia ^23,38.

Ocular comorbidities were also associated with higher odds of high myopia, consistent with findings from Beijing ³⁹. High myopia often coexists with other ocular diseases that increase the risk of severe and sometimes irreversible visual impairment, including glaucoma, retinal detachment, choroidal neovascularization, and cataracts ^4,40.

Behavioral factors were equally important. Study participants who engaged in less outdoor activity had higher odds of developing high myopia compared to those with more outdoor activity. This finding is consistent with studies conducted in Pakistan ⁴¹. During childhood, high myopia and axial elongation, a key precursor to high myopia have been associated with insufficient time spent outdoors ⁴². Numerous studies and meta-analyses have shown that increased outdoor activity is linked to a lower risk of developing myopia and slower progression of existing myopia ^43,44. The global rise in myopia prevalence has been partly attributed to modern lifestyles, where children spend more time indoors engaged in reading, studying, and screen-based activities. Reduced outdoor activity has been independently associated with increased axial elongation, which is a critical factor in the development of high myopia⁴².

Study participants engaged in more near-work activities had higher odds of being highly myopic compared to those with less near-work activity. This finding aligns with studies conducted in Taiwan ⁴⁵. High myopia is associated with near-work activities, especially prolonged reading and tasks performed at close distances. Children who engage in more near work are at a greater risk of developing myopia. To reduce this risk, it is practical to limit the duration of continuous near work and to increase the working distance ^{23,42,46–48}.

Strength and limitation

The strengths of this study include the use of a structured, pretested questionnaire alongside both objective and subjective clinical measurements, which ensured reliable and comprehensive data collection. Additionally, the study provides context-specific evidence on the prevalence of high myopia in Ethiopia, where existing data are limited, thereby offering valuable insights to inform national eye health policies, particularly those aimed at preventing and controlling myopia among youth.

However, the study has some limitations. Its cross-sectional design restricts the ability to evaluate changes in myopia over time and prevents establishing causal relationships between variables. Furthermore, some behavioral factors were self-reported, introducing the possibility of recall bias.

Conclusion and recommendation

High myopia is present among a notable proportion of secondary school students, representing a growing public health concern because of its potential sight-threatening complications. Factors such as limited outdoor activity, prolonged near-work, ocular comorbidities, and a family history of myopia were significantly associated with high myopia. Promoting outdoor activities, monitoring near-work duration, and providing counseling for students with a family history of myopia are recommended to help prevent its progression and related complications. Moreover, these findings serve as valuable baseline evidence for future longitudinal investigations and may inform the design of targeted, school-based preventive interventions.

Author contributions

AZ: conceptualization, investigation, data curation, methodology, formal analysis, software, writing original draft, funding, resource, project administration, writing review and editing. GS: investigation, data curation, methodology, formal analysis, software, writing original draft, project administration, supervision, writing review and editing. MT: validation, formal analysis, methodology, supervision, writing review and editing. BL: Data curation, Formal analysis, Methodology, Supervision, writing review and editing, and validation. AF: Formal analysis, Methodology, Supervision, writing review and editing, and validation. EM: Data curation, Formal analysis, Supervision, writing review and validation. .MM: Formal analysis, Methodology, Supervision, writing review and editing. GK: Formal analysis, Methodology, Supervision, writing review and editing, and validation. ZM: Data curation, Methodology, Supervision, writing review and editing. YA: Data curation, Formal analysis, Methodology, Supervision, writing review and editing. MM: validation, formal analysis, methodology, supervision, writing review and editing. MM: validation, formal analysis, methodology, writing review and editing..HG: formal analysis, methodology, supervision, writing review and editing. All authors read and approved the final manuscript. All authors reviewed the manuscript.

Funding

The authors declared that no financial support was received for the research, authorship, or publication of this article.

Data availability

The datasets during and/or analyzed during the current study available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval was obtained from the University of Gondar, CMHS Ethical Review Committee in accordance with the Declaration of Helsinki. Permission to conduct the study was obtained after formal letters were sent to several officials, Amhara regional institute of public health, Finote selam town zonal health office, Finote Selam Administrative Education Office, and chosen schools. Written informed consent was given to each student. Only students who provided assent and signed consent forms to participate in the study were chosen for recruitment. For those children whose age < 16, informed consent was taken from their parents or guardians and children were asked for agreement or assent to participate in this study. Every study Participants were informed about the aim of the study and they had the right of withdrawing to participate in the study. Confidentiality of the information was assured by assigning a code number and omitting the participant’s name. Participants who were found to have myopia or any other ocular disorder were referred and underwent a full ocular examination at Finote Selam General Hospital.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.