The role of outdoor activity in the development of myopia in schoolchildren.

Introduction: The aim of our study was to examine whether outdoor activity influences the prevalence of myopia in schoolchildren. Materials and methods: 5601 Polish students of elementary and secondary schools (2688 boys and 2913 girls), 6­18 years of age (mean 11.9 ±3.2 years) were examined. In every student cycloplegia after 1% tropicamide was performed. The mean spherical equivalent (SE) was calculated after examination of both eyes. Time spent on outdoor activity was evaluated based on a questionnaire. The obtained results were typed into an Excel spreadsheet and analyzed statistically using Statistica 10 software. Non-parametric tests were used due to the SE distribution being significantly different from normal distribution in the Kolmogorov­Smirnov test. The Spearman rank correlation coefficient (Rs) was used to evaluate the strength of the correlation between these variables. A p-value less than 0.05 was considered significant. Results: It has been established that with the increase in time spent on outdoor activity, the spherical equivalent of the examined students significantly increases, but the correlation is very weak (Rs = +0.036, p = 0.007). Conclusion: Outdoor activity slightly reduces the prevalence of myopia in schoolchildren.

Does the month of birth influence the prevalence of refractive errors?

PURPOSE: The aim of our study was to examine whether the month of birth influences the prevalence of refractive errors. MATERIAL AND METHODS: A total of 5,601 schoolchildren were examined (2,688 boys and 2,913 girls, aged 6-18 years, mean age 11.9, SD 3.2 years). The children examined, students of elementary and secondary schools, were Polish and resided in and around Szczecin, Poland. Every examined subject underwent retinoscopy under cycloplegia using 1% tropicamide. Data analysis was performed using the Kruskal-Wallis test followed by the Siegel and Castellan post-hoc test or the Mann-Whitney U-test. P values of < 0.05 were considered statistically significant. RESULTS: Students born in June had significantly higher spherical equivalents than schoolchildren born in May (0.66 ± 1.17 and 0.39 ± 1.17 respectively, p = 0.0058). The Mann-Whitney U-test showed that students born in June had significantly higher spherical equivalents than schoolchildren born in any other month (0.66 ± 1.17 and 0.50 ± 1.17 respectively, p = 0.0033). Besides that, we did not observe any other association between refractive errors and the month of birth. CONCLUSION: Children born in Poland in June may have a higher spherical equivalent.

Myopia and night lighting. Investigations on children with negative family history.

PURPOSE: The aim of our study was to investigate if ambient lighting at night before the age of 2 years is associated with the occurrence of myopia in a large population of Polish children. To eliminate the influence of genetic factors, only children with a negative family history of myopia were included. MATERIAL AND METHODS: A total of 3905 students, all of whom had a negative family history of myopia were examined (1800 boys and 2105 girls, aged 6-18 years, mean age 12.2, S.D. 3.3 years). The examination included retinoscopy under cycloplegia with 1% tropicamide. Myopia in the subjects was defined as a spherical equivalent of at least -0.50 dioptres. The parents of all students examined completed a questionnaire on the child's family history of myopia as well as the child's exposure to light emitted by incandescent or fluorescent lamps before the age of two years. Data analysis was performed using chi-squared Pearson test; p-values of <0.05 were considered statistically significant. RESULTS: Sleeping until the age of two with a room light is not associated with the presence of myopia during school years (p>0.05). No differences in the use of light emitted by incandescent or fluorescent lamps on the prevalence of myopia was found (p>0.05). CONCLUSIONS: Myopia is not associated with night light use before age of 2 years in a population of Polish children with a negative family history of myopia. Because both, the restricted population and results differ from our previous positive associations, perhaps early light exposure and family history/genetics interact in influcencing the occurance of myopia.

The effect of genetic factors on the occurrence of myopia.

PURPOSE: The aim of this study was to investigate on a large population if and how genetic factors have an influence on the occurrence of myopia. MATERIAL AND METHODS: A total of 5533 students were examined (2659 boys and 2874 girls, in age 6 18 years, mean age 11.9, S.D. 3.2). The examination included retinoscopy under cycloplegia induced with 1% tropicamide. Myopia was defined as a spherical equivalent of at least -0.5 dioptres. The students and their parents completed a questionnaire on the child's family history of myopia. Data analysis was performed using chi-squared test; p-values of < 0.05 were considered statistically significant. RESULTS: It was found that myopia occurs more often in students whose father (p < 0.001), mother (p < 0.001) or siblings (p < 0.0001) have myopia. A relation between the occurrence of myopia in grandparents and grandchildren was not observed (p > 0.05). CONCLUSIONS: The obtained results indicate that genetic factors have a significant effect on the occurrence of myopia.

Reading, writing, working on a computer or watching television, and myopia.

PURPOSE: The aim of our study was to investigate on a large population if reading, writing, working on a computer or watching television might be associated with the occurrence of myopia. MATERIAL AND METHODS: A total of 5865 schoolchildren were examined (2792 boys and 3073 girls, at the age 6-18 years, mean age 11.9, S.D. 3.3). The examination included retinoscopy under cycloplegia induced with 1% tropicamide. Myopia was defined as a spherical equivalent of at least -0.50 dioptres. Mean refractive error was -1.2, SD 1.3. (The students and their parents completed a questionnaire on the child's visual work. Data analysis was performed using independence chi-squared Pearson test; p-values of <0.05 were considered statistically significant. RESULTS: It was observed that myopia occurs more often in students who read and write >2 hours/day (p<0.001), and also work >0.8 hours/day on a computer (p<0.01). Furthermore, no increase in the prevalence of myopia in subjects who spend >2 hours/day watching television was found (p>0.05). CONCLUSIONS: The obtained results indicate that reading, writing, working on a computer might be associated with the occurrence of myopia among schoolchildren. Watching television is not related to the occurrence of myopia.

Prevalence of myopia and hyperopia among urban and rural schoolchildren in Poland.

INTRODUCTION: Myopia and hyperopia have a significant clinical meaning as they can be the cause of low visual acuity or even blindness. Therefore, there is a high demand for all clinical investigations regarding the development of the eye and the creation of refractive errors. Nevertheless, not many papers have been published around the world which compared the prevalence of myopia as well as hyperopia among metropolitan and provincial schoolchildren. Whereas, in Poland there was not a single paper yet published concerning this topic. That is why the aim of this paper is to describe the prevalence of myopia and hyperopia among urban and rural schoolchildren in Poland. MATERIAL AND METHODS: 2206 students were examined 1155 boys and 1051 girls, aged 10-14 years, mean age 11.9 (SD = 1.4). 614 boys in the age of 11.8 years (SD = 1.4) lived in the city, as 541 boys in the age of 11.9 years (SD = 1.4) lived in the countryside. 586 girls in the age of 11.8 years (SD = 1.5) lived in the city, as 465 girls in the age of 11.9 years (SD = 1.4) lived in the countryside. The examined students were Caucasian and lived in Szczecin, Poland or in villages located near Szczecin. The examination included retinoscopy under cycloplegia. The refractive error readings were expressed as spherical equivalent (SE). Myopia was defined as SE of at least -0.5 D, hyperopia as SE of at least +1.5 D. Astigmatism among students with myopia and hyperopia was smaller than 1 DC. Data analysis was performed using chi2 test. P values of less than 0.05 were considered statistically significant. RESULTS: It was observed that myopia occurred more frequently among children living in the city than in the countryside. 13.9% urban and 7.5% rural schoolchildren had myopia (p < 0.001)--table 1. Furthermore, it was found that hyperopia is less frequent among children living in the city than in the countryside. 7.1% urban and 30.8% rural students had hyperopia (p < 0.001)--table 2. It was determined that the average refractive error is lower among children from the city than the countryside--table 3. CONCLUSION: Living in an urban or a rural environment may have an influence on the occurrence of myopia and hyperopia among schoolchildren.

Prevalence of myopia and hyperopia in a population of Polish schoolchildren.

PURPOSE: The aim of this study was to determine the prevalence of myopia and hyperopia in a population of Polish schoolchildren. METHODS: A total of 4422 students were examined (2107 boys and 2315 girls, aged 6-18 years, mean age 11.1, S.D. 3.5). The examination included retinoscopy under cycloplegia induced with 1% tropicamide. Myopia was defined as a spherical equivalent (SE) of at least -0.5 dioptres (D), and hyperopia as a SE of at least +1.0 D. Data analysis was performed using Spearman's rank correlation coefficients and chi-squared test; p-values of <0.05 were considered statistically significant. RESULTS: It was observed that 13.3% of Polish students in the age group ranging from 6 to 18 years were myopic while 13.1% of students were hyperopic. Furthermore, a positive correlation was found between the prevalence of myopia and age (p < 0.001) and a negative correlation between prevalence of hyperopia and age (p < 0.001). It was observed that the prevalence of myopia increases substantially between 7 and 8 years of age (p < 0.01). Moreover, it was determined that with age the average refractive error among schoolchildren becomes more myopic (p < 0.001). CONCLUSIONS: The occurrence, degree and progress of myopia and hyperopia in Poland is similar to that in other European countries with a predominantly Caucasian population.

Role of gender in the occurrence of refractive errors.

PURPOSE: The aim of the paper was to study the role of gender in the occurrence of refractive errors in schoolchildren ranging from 6-18 years of age. MATERIAL AND METHODS: 5865 children from elementary schools, junior high schools and high schools were examined (2845 boys, aged 6-18 years, mean age 11.4, SD = 3.0 and 3020 girls, aged 6-18 years, mean age 11.9, SD = 3.3). 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, hyperopia as SE of at least +1.0 D. Astigmatism was diagnosed when the difference in the refraction of axes in one eye was > 0.5 DC. Data analysis was performed using chi2 test. P values of less than 0.05 were considered statistically significant. RESULTS: It was found that myopia occurs more frequently in girls (7.4%) than in boys (5.1%) - p < 0.001. Hyperopia occurs more frequently in boys (19.6%) than in girls (18.2%) - p < 0.001. A slightly higher prevalence of astigmatism in girls (1.9%) than in boys (1.5%) was also observed (p > 0.05). CONCLUSIONS: Gender influences the occurrence of myopia and hyperopia in schoolchildren ranging from 6-18 years of age.

Prevalence of refractive errors in schoolchildren ranging from 6 to 18 years of age.

PURPOSE: The aim of the paper was to study the prevalence of myopia, hyperopia and astigmatism in schoolchildren ranging from 6-18 years of age. MATERIAL AND METHODS: 5724 children from elementary schools, junior high schools and high schools were examined (2765 boys and 2959 girls, aged 6-18 years, mean age 11.7, SD = 3.2). The examined students were Caucasian and resided in and around Szczecin, Poland. The examination included retinoscopy under cycloplegia. The refractive error readings were expressed as the spherical equivalent (SE). Myopia was defined as SE of at least -0.5 D, hyperopia as SE of at least +1.0 D. Astigmatism was diagnosed when the difference in the refraction of axes in one eye was greater than 0.5 DC. The statistical analysis of data was performed by calculating the linear correlation coefficients and the coefficients for the regression equation. Additionally, Spearman's rank correlation coefficient was calculated. P values of less than 0.05 were considered statistically significant. RESULTS: It was observed that 13% of Polish students in the age group from 6 to 18 were myopic, 38% of students were hyperopic and 4% were astigmatic. Besides, a positive correlation was found between the prevalence of myopia and age (p <0.001) as well as a negative correlation between prevalence of hyperopia and age (p < 0.001). An association between the prevalence of astigmatism and age was not observed.

The influence of low birth weight on the prevalence of refractive errors among schoolchildren.

PURPOSE: The aim of the study was to determine in a large population whether low birth weight has an influence on the prevalence of refractive errors among schoolchildren. MATERIAL AND METHODS: 3663 schoolchildren were examined (1738 boys and 1925 girls, aged 6-17 years, mean age 11.1, SD = 3.2). The weight at birth was 1500-2500 grams (mean 2184, SD = 271) in 254 and more than 2500 grams (mean 3398, SD = 441) in the remaining 3409 children. Skiascopy with cycloplegia was done and refractive error readings were reported as the spherical equivalent (SE). Myopia was defined as SE < or = -0.5 D, hyperopia as SE > or = +1.5 D. Anisometropia was diagnosed when the difference in the refraction of both eyes was > 1.0 D. The parents completed a questionnaire on the child's weight and term of birth. Data analysis was performed using chi-square test. P values of less than 0.05 were considered statistically significant. RESULTS: Hyperopia was observed more frequently in 6-7 year-old children whose birth weight was > 2500 grams (p < 0.05) - table 1. Additionally, it was found that anisometropia was less frequent in 10-11 year-old children whose birth weight was > 2500 g (p < 0.05) - table 2. CONCLUSION: Low birth weight may have an effect on the prevalence of refractive errors among schoolchidren.

[Occurrence of hyperopia among students ranging from 6 to 18 years of age]. / Wystepowanie nadwzrocznosci wsród uczniów w wieku od 6 do 18 lat.

PURPOSE: To determine the prevalence of hyperopia among students ranging from 6 to 18 years of age. MATERIAL AND METHODS: 5023 students from elementary schools, junior high schools and high schools, aged 6-18 years were examined. Measurements of visual acuity as well as retinoscopy after cycloplegia have been carried out. The data was analyzed using chi-square test, u-test and Student's t-test. RESULTS: It was found that 21% of the students, aged from 6 to 18 suffers from hyperopia. It has been observed that from the sixth to the eighteenth years of life along with the age decreases the prevalence of hyperopia. A major decrease in the frequency of hyperopia occurrence among students aged between 6 and 9 years old as well as among those aged 16 and older, has been found. Significant differences between prevalence of hyperopia among boys and girls was not observed.

[Occurrence of anisometropia among students ranging from 6 to 18 years of age]. / Wystepowanie róonowzrocznosci u uczniów w wieku od 6 do 18 lat.

PURPOSE: To determine the prevalence of anisometropia among students ranging from 6 to 18 years of age. MATERIAL AND METHODS: 5023 students from elementary schools, junior high schools and high schools, aged 6-18 years were examined. Measurements of visual acuity as well as retinoscopy after cycloplegia have been carried out. The data were analyzed using chi-square test and the coefficients of rang Spearman's correlation were calculated. RESULTS: It was found that 6% of the students suffer from anisometropia. No influence of the students' age on the prevalence of anisometropia was observed. It was found that anisometropia occurs more frequently among boys than among girls.

Occurrence of refractive errors among students who before the age of two grew up under the influence of light emitted by incandescent or fluorescent lamps.

PURPOSE: The aim of the study was to determine whether the development of refractive errors could be associated with exposure to light emitted by incandescent or fluorescent lamps. MATERIAL AND METHODS: 3636 students were examined (1638 boys and 1998 girls, aged 6-18 years, mean age 12.1, SD 3.4). The examination included skiascopy with cycloplegia. Myopia was defined as refractive error < or = -0.5 D, hyperopia as refractive error > or = +1.5 D, astigmatism as refractive error > 0.5 DC. Anisometropia was diagnosed when the difference in the refraction of both eyes was > 1.0 D. The parents of all the students examined completed a questionnaire on the child's light exposure before the age oftwo. Data were analyzed statistically with the chi2 test. P values of less than 0.05 were considered statistically significant. RESULTS: It was observed that sleeping until the age of two in a room with a light turned on is associated with an increase in the occurrence of anisometropia (p < 0.02) as well as with a reduction in the prevalence of emmetropia (p < 0.05). It was also found that light emitted by fluorescent lamps leads to more frequent occurrence of astigmatism (p < 0.01).

[Astigmatism among students ranging from 6 to 18 years of age]. / Wystepownie niezbornosci wsród uczniów w wieku od 6 do 18 lat.

PURPOSE: To determine the prevalence of astigmatism among students ranging from 6 to 18 years of age. MATERIAL AND METHODS: 5023 students from elementary schools, junior high schools and high schools, aged 6-18 years were examined. Measurements of visual acuity as well as retinoscopy after cycloplegia have been carried out. The data was analyzed using chi-square test, and the coefficients of rang Spearman's correlation were calculated. RESULTS: It was found that 4% of the students, aged from 6 to 18 suffers from astigmatism. No influence of the students' age on the prevalence of astigmatism was observed. It was found that astigmatism occurs more frequently among boys rather than girls.

Role of light emitted by incandescent or fluorescent lamps in the development of myopia and astigmatism.

BACKGROUND: The purpose of our study was to determine if the development of refractive errors night be associated with exposure to light emitted by incandescent or fluorescent lamps. MATERIAL/METHODS: 3377 students from elementary schools, junior high schools and high schools were examined, aged 6-19 years. Visual acuity was measured, and retinoscopy was performed after cycloplegia. The parents of all students examined completed a questionnaire concerning the child's exposure to light emitted by incandescent or fluorescent lamps before the age of two. The data was analyzed using the chi-squared test. RESULTS: Sleeping till the age of two with a room light turned on leads to an increase in the occurrence of myopia (P<0.01). It was also found that light emitted by fluorescent lamps leads to more frequent occurrence of astigmatism (P<0.01). CONCLUSIONS: Disturbance of the daily light/dark cycle over the time during which refraction develops may disrupt emmetropization and lead to refractive errors.

Refractive errors among students occupying rooms lighted with incandescent or fluorescent lamps.

The purpose of the study was to determine whether the development of refractive errors could be associated with exposure to light emitted by incandescent or fluorescent lamps. 3636 students were examined (1638 boys and 1998 girls, aged 6-18 years, mean age 12.1, SD 3.4). The examination included retinoscopy with cycloplegia. Myopia was defined as refractive error < or = -0.5 D, hyperopia as refractive error > or = +1.5 D, astigmatism as refractive error > 0.5 DC. Anisometropia was diagnosed when the difference in the refraction of both eyes was > 1.0 D. The children and their parents completed a questionnaire on exposure to light at home. Data were analyzed statistically with the chi2 test. P values of less than 0.05 were considered statistically significant. It was found that the use of fluorescent lamps was associated with an increase in the occurrence of hyperopia (P < 0.01). There was no association between sleeping with the light turned on and prevalence of refractive errors.

[Occurrence of myopia among Polish students aged 6 to 18 years old]. / Wystepownie krótkowzrocznosci wsród uczniów w wieku od 6 do 18 lat.

PURPOSE: To determine the prevalence of myopia among students ranging from 6 to 18 years of age. MATERIAL AND METHODS: 5023 students in all, from elementary schools, junior high schools and high schools, aged 6-18 years were examined. Measurements of visual acuity as well as retinoscopy after cycloplegia have been carried out. The data was analysed using chi-square test. RESULTS: It was found that 15% of the students, aged from 6 to 18 suffers from myopia. It has been observed that from the sixth to the eighteenth years of life along with the age grows the prevalence was well as value of myopia. A major increase in the frequency of myopia occurrence among students over the age of 14 has been found. Significant differences between prevalence of myopia among boys and girls was not observed. CONCLUSIONS: (1) 15% of students in the age from 6 to 18 suffer from myopia. (2) Along with the age the prevalence of myopia increases.