Myopia: Risk Factors, Disease Mechanisms, Diagnostic Modalities, and Therapeutic Options 2019View this Special Issue
Role of Gender in the Prevalence of Myopia among Polish Schoolchildren
Purpose. The aim of the paper was to study the role of gender in the progression of myopia among Polish schoolchildren. Materials and Methods. 4875 children from elementary schools and high schools were examined (2470 boys, aged 6–16 years, mean age 11.0, SD = 2.6 and 2405 girls, aged 6–16 years, mean age 11.1, SD = 2.6). The examined students were Caucasian and resided in and around Szczecin, Poland. The examination included retinoscopy under cycloplegia. The refractive error readings were reported as spherical equivalent (SE). Myopia was defined as SE of at least −0.5 D. Data analysis was performed using the Mann–Whitney test and 2-sided Fisher’s exact test. values of less than 0.05 were considered statistically significant. Results. It was found that the SE among Polish boys is similar to the SE among Polish girls before the age of 9 years. However, in older children, lower SE values and higher prevalence of myopia were found among girls than boys, both at 9–13 years range (0.45 ± 1.05 vs 0.55 ± 1.23 D, and 8.30% vs 5.71%, , respectively) and at 13–16 years range (0.32 ± 1.14 vs 0.54 ± 1.08 D, and 10.37% vs 5.96%, ), respectively. Conclusions. Gender is associated with the prevalence of myopia among Polish schoolchildren ranging from 9 to 16 years of age.
Several studies have been carried out in different countries on the role of gender in the progression of myopia among schoolchildren. In Poland, only one paper dealing with the issue has been published [1–12].
Several contradictory results from these studies can be found in the world literature. However, most researchers point to a more frequent occurrence of myopia in girls [1–6, 9, 11, 12] than in boys [7, 8] (Table 1).
Due to the discrepancies in the obtained data, we decided to examine the spherical equivalent (SE) on a large population of 4875 Polish students after cycloplegia with 1% tropicamide.
2. Materials and Methods
The studies were carried out from October 2000 to March 2009. 4875 children from elementary schools and high schools were examined (2470 boys, aged 6–16 years, mean age 11.0, SD = 2.6 and 2405 girls aged 6–16 years, mean age 11.1, SD = 2.6). The examined students were Caucasian and resided in and around Szczecin, Poland.
Twenty-one schools were selected by random sampling out of 210 schools from the area of Szczecin. All children from the selected schools were invited to participate in the study. However, only 95.8% accepted to participate. We did not observe differential dropout.
Every examined student had undergone the following examinations: distance visual acuity testing, cover test, anterior segment evaluation, and cycloplegic retinoscopy after instillation of 1% tropicamide, and a questionnaire was taken. The methodology of the examinations has been described in detail in previous work.
Data analysis was performed using the Mann–Whitney test and 2-sided Fisher’s exact test. values of less than 0.05 were considered statistically significant .
It was found that the spherical equivalent among Polish boys is similar to the SE among Polish girls before the age of 9 years. However, in older children, lower SE values and higher prevalence of myopia were found among girls than boys, both at 9–13 years range (0.45 ± 1.05 vs 0.55 ± 1.23 D, and 8.30% vs 5.71%, , respectively) and at 13–16 years range (0.32 ± 1.14 vs 0.54 ± 1.08 D, and 10.37% vs 5.96%, ), respectively (Figure 1, Tables 2 and 3).
It is widely known that myopia occurs more often in pupils who spend a lot of time reading, writing, or using a computer [13–15]. Myopia occurs less often in pupils who spend a lot of time doing outdoor activities [13, 14, 16]. It is widely regarded that myopia occurs more often in girls than in boys, especially in older children. In our study, we also observed a higher occurrence of myopia in girls aged 9 to 16 years. A similar relationship was observed by other authors. Only Maul et al.  in Chile concluded that myopia occurs more often in boys aged 5–15 years.
In order to reduce the possibility of making a mistake, we decided to conduct the examinations on a large population of 4875 students after cycloplegia with 1% tropicamide. Besides, the examinations were performed only by two doctors. According to Zadnik et al. , 95% limits of agreement for cycloplegic retinoscopy are ±0.95 D.
Based on the conducted examinations, we found that in Polish schoolchildren, with age, a decrease in the spherical equivalent occurs. A faster and larger decrease was observed in girls compared to boys. This may indicate that myopia occurs earlier and more often in girls than in boys. In 2007, we published a similar paper on the prevalence of refractive errors among children aged 6–18 years. We concluded that the prevalence of myopia among boys was 5.1% and among girls was 7.4% .
The data obtained by us are similar to the results of investigations performed in India , Poland , Armenia , Malaysia , Taiwan , Australia , Finland , Nepal , Singapore , and China . However, they differ from the results gathered in Hong Kong  and Chile .
It is widely accepted that there are two possibilities for gender differences. The first is that the differences are biologically determined. The second possibility is that they are socially/behaviorally determined.
Zylbermann et al.  determined that Orthodox Jewish boys, who receive an intensive religious education, are much more myopic than their sisters and the rest of their age cohort who receive a more secular education. Probably, the high degree and prevalence of myopia observed in the Orthodox male group may be due to their heavy accommodative eye use attributed to their different study habits.
Recent extensive studies carried out in China on the prevalence of myopia have concluded that myopia occurs more often in girls. Ma et al.  have shown that myopia occurs more often in girls below 3 years of age. However, Li et al.  concluded that myopia occurs more often in 12.7-year-old girls.
According to Krause et al. , the reasons for sex differences are determined by genetic factors, dietary factors, and amount of close work, as well as are connected with puberty. Girls reach puberty earlier than boys and therefore reach their final body height one or two years earlier than boys. This leads to a rise in the prevalence of myopia.
Our results are similar to the results obtained by other authors. We also demonstrated that gender is associated with the prevalence of myopia.
Gender is associated with the prevalence of myopia among Polish schoolchildren ranging from 9 to 16 years of age.
The data used to support the findings of this study are available from the corresponding author upon request.
Conflicts of Interest
The authors declare that there are no conflicts of interest regarding the publication of this paper.
I. Ahmed, S. Mian, S. Mudasir, and K. I. Andrabi, “Prevalence of myopia in students of Srinagar City of Kashmir, India,” International Journal of Health Sciences, vol. 2, no. 1, pp. 77–81, 2008.View at: Google Scholar
D. Czepita, A. Mojsa, M. Ustianowska, M. Czepita, and E. Lachowicz, “Role of gender in the occurrence of refractive errors,” Annales Academiae Medical Stetinensis, vol. 53, no. 2, pp. 5–7, 2007.View at: Google Scholar
D. Czepita, “Myopia: incidence, pathogenesis, management and new possibilities of treatment,” Russian Ophthalmological Journal, vol. 7, no. 1, pp. 96–101, 2014.View at: Google Scholar
M. Czepita, L. Kuprjanowicz, K. Safranow et al., “The role of outdoor activity in the development of myopia in schoolchildren,” Pomeranian Journal of Live Sciences, vol. 62, no. 4, pp. 30–32, 2016.View at: Google Scholar
K. Zadnik, D. O. Mutti, and A. Adams, “The repeatability of measurement of the ocular components,” Investigative Ophthalmology & Visual Science, vol. 33, no. 7, pp. 2325–2333, 1992.View at: Google Scholar
R. Zylbermann, D. Landau, and D. Berson, “The influence of study habits on myopia in Jewisch teenagers,” Journal of Pediatric Ophthalmology & Strabismus, vol. 30, no. 5, pp. 319–322, 1993.View at: Google Scholar