PREVALENCE OF MYOPIA AND HYPEROPIA AMONG URBAN AND RURAL SCHOOLCHILDREN IN POLAND

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1 ANNALES ACADEMIAE MEDICAE STETINENSIS ROCZNIKI POMORSKIEJ AKADEMII MEDYCZNEJ W SZCZECINIE 2008, 54, 1, DAMIAN CZEPITA, ARTUR MOJSA, MARIA ŻEJMO 1 PREVALENCE OF MYOPIA AND HYPEROPIA AMONG URBAN AND RURAL SCHOOLCHILDREN IN POLAND CZĘSTOŚĆ WYSTĘPOWANIA KRÓTKOWZROCZNOŚCI I NADWZROCZNOŚCI WŚRÓD UCZNIÓW MIEJSKICH I WIEJSKICH W POLSCE Katedra i Klinika Okulistyki Pomorskiej Akademii Medycznej w Szczecinie al. Powstańców Wlkp. 72, Szczecin Kierownik: prof. dr hab. n. med. Danuta Karczewicz 1 Katedra i Zakład Mikrobiologii i Immunologii Pomorskiej Akademii Medycznej w Szczecinie al. Powstańców Wlkp. 72, Szczecin Kierownik: prof. dr hab. n. med. Stefania Giedrys-Kalemba Streszczenie Wstęp: Krótkowzroczność i nadwzroczność mają duże znaczenie kliniczne ponieważ mogą prowadzić do obniżenia ostrości wzroku, a nawet do ślepoty. Dlatego też istnieje duże zapotrzebowanie na wszelkie badania kliniczne dotyczące rozwoju oka oraz powstawania wad refrakcji. Pomimo tego do tej pory na świecie nie opublikowano zbyt wielu prac porównujących częstość występowania krótkowzroczności i nadwzroczności wśród uczniów miejskich i wiejskich, natomiast w Polsce nie opublikowano żadnej. Dlatego celem pracy było opisanie częstości występowania krótkowzroczności i nadwzroczności wśród dzieci miejskich i wiejskich w Polsce. Materiał i metody: Przebadano 2206 uczniów (1155 chłopców i 1051 dziewcząt w wieku lat, średni wiek 11,9 lat, SD = 1,4). 614 chłopców w wieku 11,8 lat (SD = 1,4) mieszkało w mieście, a 541 chłopców w wieku 11,9 lat (SD = 1,4) mieszkało na wsi. 586 dziewcząt w wieku 11,8 lat (SD = 1,5) mieszkało w mieście, a 465 dziewcząt w wieku 11,9 lat (SD = 1,4) mieszkało na wsi. Badani uczniowie należeli do rasy kaukaskiej, mieszkali w Szczecinie lub na wsiach w pobliżu Szczecina. Wykonywano skiaskopię po cykloplegii. Wyniki wad refrakcji wyrażono w formie ekwiwalentu sferycznego (SE). Przyjęto, że w krótkowzroczności SE < -0,5 D, a w nadwzroczności SE > +1,5 D. Astygmatyzm wśród uczniów z krótkowzrocznością i nadwzrocznością był mniejszy od 1 DC. Analizę danych przeprowadzono testem χ 2. Przyjęto poziom istotności p < 0,05. Wyniki: Zaobserwowano, że krótkowzroczność występuje częściej u dzieci mieszkających w mieście niż na wsi. Krótkowzroczność miało 13,9% uczniów miejskich oraz 7,5% wiejskich (p < 0,001) tabela 1. Poza tym stwierdzono, że nadwzroczność występuje rzadziej u dzieci mieszkających w mieście niż na wsi. Nadwzroczność miało 7,1% uczniów miejskich i 30,8% wiejskich (p < 0,001) tabela 2. Wykazano, że średnia wada refrakcji jest niższa wśród dzieci z miasta niż ze wsi tabela 3. Wniosek: Mieszkanie w środowisku miejskim lub wiejskim może wpływać na występowanie krótkowzroczności i nadwzroczności wśród uczniów. H a s ł a: krótkowzroczność nadwzroczność miasto wieś uczniowie. Summary 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

2 18 DAMIAN CZEPITA, ARTUR MOJSA, MARIA ŻEJMO 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 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 χ 2 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. K e y w o r d s: myopia hyperopia urban rural schoolchildren. Introduction Lately, a major increase in the frequency of myopia occurrence has been noted. This refractive error occurs more frequently in East Asia and countries with a high level of technological development. Hence, this can be linked on one side with genetic predispositions as on the other with the influence of the environment [1, 2, 3, 4, 5, 6, 7]. Among the environmental factors near visual work which is reading, writing, as well as working on the computer play the most important role. It is believed that other environmental factors especially like whether we live in a city or a village play a lesser role in the creation and progress of myopia. That is why not a lot of attention has been focused on them [1, 2, 5, 6, 7]. On the other hand hyperopia prevalent among children is in a lesser degree linked with the influence of the environment. Children are born with physiological hyperopia. With age the optical components in the eyeball change, and hyperopia gradually decreases [1, 3, 4]. 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 [1, 2, 5, 7]. 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 [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]. 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 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 children, students of elementary and secondary schools, were examined in the school s consulting rooms. The examined students were Caucasian and lived in Szczecin, Poland or in villages located near Szczecin. Participation was voluntary and informed consent was obtained from the school principals and parents of all the children. The studies were approved by the Bioethics Committee of the Pomeranian Medical University. The research protocol adhered to the provisions of the Declaration of Helsinki for research involving human subjects. The examination included retinoscopy under cycloplegia induced with two drops of 1% tropicamide instilled 5 minutes apart to each eye. Thirty minutes after the last drop retinoscopy was performed. Retinoscopy was performed in a dark room and all schoolchildren were examined by the some doctor (AM). According to Zadnik et al. [25] 95% limits of agreement for cycloplegic retinoscopy are D. The refractive error readings were expressed as spherical equivalent (SE) (sphere power plus half negative cylinder power). 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. Both eyes were examined though data gathered from the right eye were analyzed. Data analysis was performed using χ 2 test. P values of less than 0.05 were considered statistically significant.

3 PREVALENCE OF MYOPIA AND HYPEROPIA AMONG URBAN AND RURAL SCHOOLCHILDREN IN POLAND 19 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. Discussion Although the environmental conditions have a big influence on the creation and progress of myopia until now only a few works have came out in which a comparison in the prevalence of myopia as well as hyperopia in the countryside and in the city has been done [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]. The first studies concerning this matter have been carried out in in India. It was than found that myopia occurs more frequently among the urban population and people with higher education and higher income [17]. Age (years) Wiek (lata) T a b l e 1. Prevalence of myopia (SE < -0.5 D) among urban and rural schoolchildren in Poland T a b e l a 1. Częstość występowania krótkowzroczności (SE < -0,5 D) wśród uczniów miejskich i wiejskich w Polsce with myopia z krótkowzrocznością with myopia z krótkowzrocznością difference różnica N N % N N % % < < > > < Age (years) Wiek (lata) < T a b l e 2. Prevalence of hyperopia (SE > +1.5 D) among urban and rural schoolchildren in Poland T a b e l a 2. Częstość występowania nadwzroczności (SE > +1,5 D) wśród uczniów miejskich i wiejskich w Polsce with hyperopia z nadwzrocznością with hyperopia z nadwzrocznością difference różnica N N % N N % % < < < < < Age (years) Wiek (lata) < T a b l e 3. Average refractive error among urban and rural schoolchildren in Poland T a b e l a 3. Średnia wada refrakcji wśród uczniów miejskich i wiejskich w Polsce N mean średnia SD N mean średnia SD mean / średnia p p

4 20 DAMIAN CZEPITA, ARTUR MOJSA, MARIA ŻEJMO T a b l e 4. Prevalence of myopia (SE < -0.5 D) and hyperopia (SE > D) among schoolchildren of different countries T a b e l a 4. Częstość występowania krótkowzroczności (SE < -0,5 D) i nadwzroczności (SE > + 2,0 D) wśród uczniów różnych krajów Authors Autorzy Maul et al. Pokharel et al. Zhao et al. Dandona et al Murthy et al Naidoo et al He et al Goh et al Country Kraj Chile Chile Nepal Nepal China Chiny India Indie India Indie South Africa RPA China Chiny Malaysia Malezja Area / Środowisko Age (years) Wiek (lata) Myopia (%) Krótkowzroczność (%) Hyperopia (%) Nadwzroczność (%) Urban / Miejskie Rural / Wiejskie Rural / Wiejskie Rural / Wiejskie Urban / Miejskie Semirural/urban Podmiejskie/miejskie Urban / Miejskie Urban / Miejskie In 1970 Said et al. [21] described the prevalence and causes of blindness in urban and rural areas of Egypt. In all they had examined people from and around Alexandria. They have proven that myopia occurs more frequently in the city than the countryside and is the third ranking cause of blindness among urban residents. Extensive epidemiological studies on the prevalence of myopia were carried out in the years 1983 in Taiwan. All together students have been examined and it was observed that myopia occurs more frequently in metropolitan than in provincial schools located in Taiwan. This correlation was justified by a lot of near-work activity among students of city schools [8, 13, 14]. In results of several studies done in rural and urban areas of China, Nepal and the Sultanate of Oman have been published. In those studies it was also found that myopia occurs more frequently among students from the city rather than from the countryside and is associated with intensive near-work as well as having a father with higher levels of education [10, 15, 22]. Recently, a series of population-based surveys of refractive errors and visual impairment among schoolchildren (Refractive Error Study in Children RESC) were conducted in several different countries, all using the same protocol [26]. The results of these studies show that myopia has a higher prevalence among urban students than in rural schoolchildren. However, the occurrence of hyperopia among metropolitan students is lower than in provincial schoolchildren [9, 11, 12, 16, 18, 19, 20, 24] table 4. Only in studies carried out in Australia Wensor et al. [23] have shown that there was no significant difference in myopia rates between urban and rural populations. Although, this was probably because the authors examined subjects in the ages of years old but not school age children. However, a more frequent occurrence of myopia was observed among people with higher education, clerks, professionals, people born in southeast Asia, and people with high degrees of nuclear opacity. On the whole the majority of authors come to similar conclusions and state that myopia occurs more frequently in metropolitan schools than in provincial. It is assumed that this is caused by more intensive near-work among urban than rural schoolchildren [8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]. This dependency was also observed in the carried out work. Perhaps it might have been caused by the increased intensiveness of visual work among students living in the city. Additionally it was found that the average refractive error is lower among urban than rural schoolchildren. As this might be linked with the functioning of genetic factors rather than environmental. Conclusion Living in an urban or a rural environment may have an influence on the occurrence of myopia and hyperopia among schoolchildren. Acknowledgments We would like to thank A. Pechmann for assistance during data collection. References 1. Czepita D.: Refractive errors (in Polish with English abstract). Lekarz, 2007, 11, Czepita D.: Myopia epidemiology, pathogenesis, present and coming possibilities of treatment. Case Rep. Clin. Pract. Rev. 2002, 3,

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