검안및콘택트렌즈학회지 2017 년제 16 권제 2 호 Ann Optom Contact Lens 2017;16(2):58-63 ISSN 2384-0919 (Print) ISSN 2384-0927 (Online) Original Article 한국성인의굴절이상형태, 유병률및분포에관한조사 A Comparative Study of Prevalence, Distribution and Patterns of Refractive Error in Korean Adults 이인호 1 김호윤 2 이종수 1 In Ho Lee, MD 1, Ho Yoon Kim, MD 2, Jong Soo Lee, MD, PhD 1 부산대학교의과대학부산대학교병원안과 1, 메리놀병원안과 2 Department of Ophthalmology, Pusan National University Hospital 1, Busan, Korea Department of Ophthalmology, Maryknoll Medical Center 2, Busan, Korea Purpose: To investigate the prevalence, distribution and patterns of refractive error in Korean adults, and to analyze the basic data for ophthalmologic examination of the Korean National Health and Nutrition Examination Survey. Methods: This study was conducted using the results of the eye health screening conducted January 2008 to December 2012 in the Korean National Health and Nutrition Examination Survey. A total of 13,916 Korean adults were divided into three age groups, 20 to 29 years, 30 to 39 years, and 40 to 49 years of age. We investigated over the past five years of the prevalence, distribution and pattern of refractive error of them. Furthermore, we also examined the prevalence of myopia according to the living area, final graduate state, income of subjects, and incidence of myopia in children depending on the subject s myopia for 3,374 people. Results: Of the 13,916 people who have undergone ophthalmic examination for the past 5 years, 5,901 (42.4%) were male and 8,015 (57.6%) were female. The prevalence of refractive error was 53.6% in myopia, 38.9% in emmetropia, 6.4% in high myopia, and 1.2% in hyperopia. The prevalence of total myopia was the highest at 71.3% in the 20s and gradually decreased with age and was 50.0% in 40s. The prevalence of myopia in each year tended to increase gradually from 2008 to 2012, and similar findings were observed in all age groups. The prevalence of myopia was higher in the urban area, when the final educational attainment was high, and when the household income was high (p<0.001). Myopia was observed in children at a significantly higher rate when parents had myopia (p=0.001). Conclusions: The prevalence of myopia according to year has increased gradually from 2008 to 2012 in refractive error distribution of Korean adults for the past 4 years, especially in urban areas and high educational attainment or high household income. Ann Optom Contact Lens 2017;16(2):58-63 Key Words: Prevalence of myopia; Korean adult; Myopia; Refractive error 굴절이상은물체로부터망막표면에정확한상이맺히지 못하여발생하는데, 그중근시는일반적으로시력적인불 Received: 2017. 4. 6. Revised: 2017. 4. 28. Accepted: 2017. 4. 28. Address reprint requests to Jong Soo Lee, MD, PhD Pusan National University Hospital, #179 Gudeok-Ro, Seo-gu, Busan 49241, Korea Tel: 82-51-240-7326, Fax: 82-51-240-7341 E-mail: jongsool@pusan.ac.kr 편함이외에특별한문제를일으키지않지만고도근시등과같이정도가심한경우에는녹내장, 백내장, 망막박리, 근시성황반변성등과같은시력을상실하는질병의원인이된다. 고도근시로인한시력저하가약 10억명이상에서발생하는데, 1,2 일반적인굴절변화는소아기에근시의진행이시작되고 20대초반까지신체성장과함께지속되어 20 대후반가장높은근시유병률이관찰된다. 이후근시유병률의감소와함께원시유병률의증가가관찰되며 70대 Copyright 2017, The Korean Optometry Society The Korean Contact Lens Study Society Annals of Optometry and Contact Lens is an Open Access Journal. All articles are distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. 58
- 이인호외 : 한국성인의굴절이상변화 - 후반까지증가하지만, 이후백내장등의발생으로원시유병률의미세한감소가관찰된다. 난시의경우는출생첫해에약 50% 에서 1.00D 이상굴절상태를나타내다가 5세경에는 20% 로감소하며이후 40세까지큰변화가없다가 40 세이상의성인에서는도난시가증가되어 10년마다평균 0.25D씩변한다고한다. 3,4 각굴절이상의유병률은전세계지역에따라차이가있다. 최근아시아에서발표된굴절이상에대한보고에서는미주지역이나유럽에비해근시유병률이현저하게높고, 5,6 국내보고에서도우리나라의근시유병률이미국에비해높다고보고하고있다. 7 일반적으로아시아국가에서는많은학습량과학교의경쟁구도속에서생활해야하는환경이므로높은근시의발생과연관성을보인다. 이외에도부모가근시인어린이의경우정시의부모를가진어린이보다근시가될확률이 4배이상높은것으로알려진유전적요인, 조절과폭주에따른안축장의증가와조절기전, 조절시안압증가에따른공막의확장등안구와관련한생물학적요인이그원인으로대부분알려져있다. 8-10 최근국내외의보고에따르면, 성인에서근시로의이행이나유병률이과거에비해점차증가하기에미국의경우는 1980년대부터이에대한관심이높아져국민들을대상으로한굴절이상변화에대한연구가활발하게진행되었고 1999년부터 National Health and Nutrition Examination Survey (NHANES) 를통해매년굴절이상의통계를산출하고있다. 10,11 국내의경우도국민건강영양조사에 2008년도 부터안과검진이포함되면서굴절이상에대한기본적인검사를시행중이나이에대한관심이나연구는아직까지도부족한실정이다. 국내의소아와청소년기를대상으로한근시의유병률에관한연구는많으나성인남녀를대상으로근시의유병률과굴절이상변화에대한연구는미미한상태이고, 굴절이상의변화에따른성인을대상으로한정기적인안과검진에대한프로토콜또한부족한실정이다. 12-14 이에저자들은 2008년부터 2012년까지최근 4년간 20-49세의한국성인남녀를대상으로시행된국민건강영양조사의자료를바탕으로굴절이상의유병률과변화, 굴절이상의분포양상과유형을조사하고향후성인에서의굴절교정에관한검진이나대책에관한근본적인자료의방향을제시하고자한다. 대상과방법 본연구는 2008년 1월부터 2012년 12월사이에시행된국민건강영양조사를받은 45,810명중안검사를시행받은 20세에서 49세까지성인남녀 13,916명을대상으로하였다. 그리고대상자중자녀가국민건강영양조사에참여한 3,374명을대상으로굴절검사를시행하여부모의굴절검사결과에따른굴절이상여부를분석하였다. 국민건강영양조사는국민건강증진법제 16조에근거하여국민의건강과영양에관한기초통계를산출하기위한목적으로시행된 Table 1. Distribution of Korean adults by year, sex, age, region, and educational level All subjects 2008 2009 2010 2011 2012 No. % No. % No. % No. % No. % No. % Subjects 13916-1841 13.2 3814 27.4 3068 22.0 2747 19.7 2446 17.6 Age (year) 20-29 3266 23.5 461 25.0 944 24.8 683 22.3 609 22.2 569 23.3 30-39 5344 38.4 699 38.0 1396 36.6 1228 40.0 1092 39.8 929 38.0 40-49 5306 38.1 681 37.0 1474 38.6 1157 37.7 1046 38.1 948 38.8 Sex Male 5901 42.4 777 42.2 1650 43.3 1313 42.8 1153 42.0 1008 41.2 Female 8015 57.6 1064 57.8 2164 56.7 1755 57.2 1594 58.0 1438 58.8 Region Urban 11836 85.1 1539 83.6 3153 82.7 2600 84.7 2412 87.8 2132 87.2 Rural 2080 12.8 302 16.4 661 17.3 468 15.3 335 12.2 314 12.8 Education Elementary 332 2.4 54 2.9 145 3.8 62 2.0 49 1.8 22 0.9 Middle 723 5.3 133 7.2 253 6.7 128 4.2 123 4.6 86 3.6 High 6248 45.6 907 49.3 1855 48.9 1301 42.8 1155 43.0 1030 43.7 University 6410 46.7 745 40.5 1538 40.6 1549 51.0 1358 50.6 1220 51.7 Home income Lowest quartile 1017 7.4 146 8.0 327 8.7 237 7.8 175 6.4 132 5.4 Low-intermediate 3411 24.8 470 25.9 828 22.0 786 25.9 731 26.9 596 24.6 Upper-intermediate 4744 34.5 636 35.1 1296 34.4 1031 34.0 954 35.1 827 34.1 Highest quartile 4592 33.4 562 31.0 1321 35.0 976 32.2 861 31.6 872 35.9 59
- 검안및콘택트렌즈학회지 2017 년제 16 권제 2 호 - 법정조사이다. 그리고본국민건강영양조사는대한안과학회와질병관리본부가공동으로기본적인굴절이상부터주요안질환에이르기까지전반적인조사를위해시행된전국단위검진조사이다. 전체대상자를대상으로굴절검사를시행하였다. 굴절검사는조절마비제를사용하지않고자동굴절검사기를이용하여측정하여굴절치를이용하였다. 측정된굴절치는구면렌즈대응치 (spherical equivalent, SE) 로계산하여굴절이상을구분하였으며, 구면대응치를기준으로원시 (+1.00D SE), 정시 ( 0.75D < SE < 1.00D), 근시 ( 6.00D < SE 0.75D), 고도근시 (SE 6.00D) 로구분하였다. 그리고표준화된질문지를통한인터뷰를이용하여각종인자를수집하였다. 수집된각종인자들은사는지역 ( 도시 / 시골 ), 최종학력 ( 초졸이하, 중졸, 고졸, 대졸이상 ), 가족수입 ( 하, 중하, 중상, 상 ) 이다. 자료분석은 SPSS 통계프로그램 (version 18.0; SPSS Inc., Chicago, IL, USA) 을사용하여빈도분석을통하여유병률을구하였고, 각인자간비교를위해교차분석을시행하였다. 통계학적유의수준은 0.05로하였다. 결과 전체대상자는 13,916명으로남자 5,901명, 여자 8,015명이었고, 나이대별로 20대 3,266명, 30대 5,344명, 40대 5,306명이었다 (Table 1). 전체대상자의굴절이상은근시가 53.6% 로가장많았고, 정시 38.9%, 고도근시 6.4%, 원시 Table 2. Prevalence of myopia, high myopia, emmetropia, hyperopia stratified by age in Korean adults All subjects 20s (age 20-29) 30s (age 30-39) 40s (age 40-49) No. % No. % No. % No. % Myopia 7446 53.6 1979 60.6 3041 56.9 2426 45.7 High Myopia 893 6.4 348 10.7 318 6.0 227 4.3 Emmetropia 5415 38.9 901 27.6 1955 36.6 2559 48.2 Hyperopia 162 1.2 38 1.2 30 0.6 94 1.8 Total 13916 100 3266 100 5344 100 5306 100 Figure 1. Change of prevalence of myopia, high myopia, emmetropia, hyperopia between 2008 to 2012. 60
- 이인호외 : 한국성인의굴절이상변화 - Table 3. Prevalence of myopia, high myopia, emmetropia, hyperopia according to sex, region, education, home income High myopia Myopia Emmetropia Hyperopia Total No. % No. % No. % No. % No. Sex Male 345 5.8 3174 53.8 2322 39.3 60 1.0 5901 Female 548 6.8 4272 53.3 3093 38.6 102 1.3 8015 Region Urban 794 6.7 6442 54.4 4456 37.6 144 1.2 11836 Rural 99 4.8 1004 48.3 959 46.1 18 0.9 2080 Education Elementary 4 1.2 99 29.8 216 65.1 13 3.9 332 Middle 17 2.4 270 37.3 416 57.5 20 2.8 723 High 351 5.6 3237 51.8 2576 41.2 84 1.3 6248 University 512 8.0 3745 58.4 2109 32.9 44 0.7 6410 Home income Lowest quartile 73 7.2 500 49.2 421 41.4 23 2.3 1017 Low-intermediate 188 5.5 1820 53.4 1371 40.2 32 0.9 3411 Upper-intermediate 305 6.4 2551 53.8 1831 38.6 57 1.2 4744 Highest quartile 318 6.9 2495 54.3 1731 37.7 48 1.0 4592 Table 4. Distribution of prevalence of myopia according to the existence of myopia in parents between 2008 to 2012 Children Non-myopia Myopia Parents No myopic parents 468 (46.7) 535 (53.3) One myopic parents 612 (38.4) 982 (61.6) Both myopic parents 237 (30.5) 540 (69.5) Total 1317 (39.0) 2057 (61.0) Values are presented as number (%). 1.2% 이었다. 20대에서근시및고도근시가 60.6%, 10.7% 로가장높았으며 30대 59.9%, 6.0% 40대 45.7%, 4.3% 로나이가많아질수록점차감소하는경향을보였다. 이에비해정시및원시는나이가많아질수록증가하였다 (p<0.001) (Table 2). 각굴절이상의연도별양상을보면 2008 년근시및고도 근시가 50.8%, 6.1% 에서점차증가하는경향을보여 2012 년근시및고도근시가 56.3%, 6.8% 로증가하였다. 반면 정시는 2008 년 14.6% 에서 2012 년 35.7% 로증가하였다 (p=0.021). 이러한경향은 20 대에서 40 대모든연령층에서 관찰되었다 (Fig. 1). 각종인자들과굴절이상과의연관성을보면성별에따른 차이는없었으나 (p=0.051), 도시지역에서시골지역에비하 여높은근시및고도근시유병률이관찰되었다 (p<0.001). 그리고최종학력이높을수록 (p<0.001), 가정소득이높을수 록 (p=0.001) 근시및고도근시의유병률이높았다 (Table 3). 부모의근시유병과자녀의근시유병과의관계를보면부 모의근시가있을때, 특히부모양쪽이근시인경우자녀 에서근시가많이관찰되었다 (p<0.001) (Table 4). 고찰 굴절이상은전세계적으로다양한보고가있으나, 동양인에서근시유병률이서양인에비해높은것으로알려져있다. 본연구에서는 20세에서 49세사이의한국성인을대상으로근시유병률은 59.9% 이었다. 동양의성인을대상으로한보고중 Shimizu et al 15 은일본의 40세에서 79세사이성인을대상으로근시유병률을 45.7% 로보고하였고, Wong et al 16 은싱가폴의 40세에서 79세성인을대상으로근시, 원시유병률을각각 38.7%, 28.4% 로보고하였다. 2000년에전라도, 제주및서울일부지역에서징병신체검사를받은 19세남자 12,207명을대상으로한연구에서는근시유병률과고도근시유병률이각각 56.4%, 12.9% 로보고하였고, 2002년에대한민국의부산, 울산, 경남지역만 19세남자 50,234명을대상으로한연구에서근시유병률은 45.60%, 고도근시유병률은 11.50% 로나타났다. 17,18 본연구에서는 20세에서 49세사이의한국성인을대상으로근시유병률은 59.9% 으로이전의보고들보다는근시의유병률이높게나타났다. 서양의성인을대상으로한보고중 The Eye Diseases Prevalence Research Group 19 은 40세이상성인을대상으로유럽, 북미, 호주의근시유병률을각각 26.6%, 25.4%, 16.4% 로발표되어국내의근시유병률과는현저한차이를보였다. 보고간근시의진단기준, 거주지역, 조사대상자, 연구시기등이달라획일적인비교가어렵지만공통적으로아시아가아닌지역에서아시아지역에서의근시유병률보다는유의하게낮게보고됨을알수있다. 그리고동양인이아프리카나서구인에비하여근시유병률이높게나타났으며인종간의근시유병률을비교한 Kleinstein et al 20 과 Lam et al 21 의연구결과에서도동양인의 61
- 검안및콘택트렌즈학회지 2017 년제 16 권제 2 호 - 근시유병률이높게나타나는결과를보고하였다. 각연령대별전체근시유병률은 20대 71.3%, 30대 64.9%, 40대 50.0% 로 20대에서가장높은근시유병률이관찰되었으며나이가많아질수록유병률이감소하였다. 고도근시유병률역시 20대에서 10.7% 로 30대 6.0%, 40대 4.3% 에비해가장높았다. 일반적으로근시진행은소아기에시작하여 20대초반까지신체성장과함께지속된다고알려져있으며, 여자는 14.6-15.6세, 남자는 15.0-16.7세에근시진행이멈춘다고하였다. 22-24 또한 Tokoro et al 25 은 6-80세를대상으로 10년동안굴절이상을분석한결과 6-10세와 11-20세그룹의 10년간굴절력의변화는각각 -3.65D와 -2.17D로근시쪽으로진행하였고 21-40세그룹은굴절이상의변화가미미하였으며 41세에서 69세까지는원시쪽으로진행하다가 70세이상에서는다시근시쪽으로진행하는것으로나타났다. 이러한경향은 10년간한국인의굴절이상변화가 6-20세까지근시쪽으로진행하다가 70세까지원시쪽으로진행한후다시근시쪽으로진행하는것으로유사한결과를보고하였다. 7 본연구에서도역시 20대에서 40대에이르기까지점차근시유병률의감소를보이며점차원시화되는것을확인할수있었다. 본연구에서 2008년부터 2012년까지근시유병률이 56.9% 에서 2012년 63.1% 로증가되었다. 그리고근시유병률의증가는 20대에국한되지않고 40대까지모든연령층에서관찰되었다. 이러한근시유병률의증가는동양과서양모두에서보고되고있다. 아시아지역의경우타이완에서 20년간이루어진학동기학생들을대상으로한대규모연구에서근시유병률은 12세에 61%, 15세에 81%, 18세에 84% 로나타났으며특히 1983년도와비교해서유의하게근시유병률이증가하였다. 8 또한네덜란드에서 1990년에서 2008년까지시행된 population based cohort 연구에서 1990 년에서 1993년사이근시유병률이 16.4% 이었으나이후 2000년에서 2002년사이 21.9%, 2005년에서 2008년사이 32.5% 로증가된결과를보고하였다. 26 이는현대사회로올수록컴퓨터등의근거리주시나전자기기사용등으로근거리작업이많아지는사회적분위기가근시유병률증가에큰역할을한다고생각한다. 27 근시의발생은민족과인종마다차이가있으며여러가지많은요소들이관여하고있는것으로생각된다. 근시의발생및진행에영향을미치는원인에대해서는많은가설이제기되어왔지만현재까지확실히밝혀진바는없다. 일부유전적요소외에그민족의사회, 문화적인배경에의한적응과정과환경적요소, 눈모임과조절에따른안축장의증가와과도한근거리작업에따른가성근시의발생등이원인으로제기되어왔는데특히연령의증가에따른안 축장길이의증가에지속적근거리작업이영향을미치는것으로추정된다. 8-10 이는아시아지역의높은교육열과독서및컴퓨터작업등의많은근거리작업량을고려할때, 근시유병률이높은원인으로추정할수있다. 본연구에서여러상황에따른근시유병률차이를보면도시지역에서, 최종학력이높을수록, 가정수입이높을수록근시유병률이높음을확인할수있었다. Wu et al 28 은근시유병률에영향을주는인자로성별, 인종, 소득수준, 야외활동시간, 공부시간, 부모의근시여부등이있다고보고하였으며, Guo et al 29 도나이, 사는지역, 부모의교육수준, 야외활동시간, 부모의근시여부등이근시유병률에영향을줄수있다고보고하여본연구의결과와유사하였다. 추가로근시의발생요소중하나인가족력에대한영향을알아보고자한본연구에서부모의근시여부에따른자녀의근시의발생비율이부모둘다근시가없을경우 53.3% 인데반해부모둘중한명이근시인경우 61.6%, 부모둘다근시인경우 69.5% 로부모가근시인경우자녀의근시빈도가높았다. Wu et al 28 은부모근시유병이자녀근시유병에미치는영향에대한보고에서부모둘다근시가없을경우에비해한명이근시인경우교차비 2.28, 부모둘다근시인경우교차비 4.02로근시를가진부모에서자녀가근시유병이높음을보고하였고, Guo et al 29 은부모가근시일경우자녀들의안구장축길이가길어진다고보고하여본연구결과와유사한결과를보고하고있다. 본연구의한계점은 50세이상의연령층에대한자료가부족하여한국성인전체의굴절변화양상을살펴볼수없었다는점과국민건강영양조사의안검진은일반건강검진자료로같은사람이지속적으로검진받는것이아니며직업, 환경, 기저질환에대한자료가부족하고다른질환과의연관성유무도밝히기어렵다는문제점이있었다. 의료의발전에도아직국민보존건강에대한요구및한계가있으며국민기초건강의각종지표를통해이를정확히예측하고연구하여전국민을대상으로한다양한질병의유병률과위험인자를분석할필요가있다. 눈은우리인체에서가장중요한기관중하나로근시진행에따른성인을대상으로굴절이상을유발하는조절가능한위험인자들을분석하고정기적인굴절검사를통한적절한시력교정이필요하다. 아울러근시인부모에게서는태어난자녀에게서는조기에굴절검사및근시의진행을억제하는안과적인진료에대한적극적인홍보가요구된다. REFERENCES 1) Mitchell P, Hourihan F, Sandbach J, Wang JJ. The relationship be- 62
- 이인호외 : 한국성인의굴절이상변화 - tween glaucoma and myopia: the Blue Mountains Eye Study. Ophthalmology 1999;106:2010-5. 2) Risk factors for idiopathic rhegmatogenous retinal detachment. The Eye Disease Case-Control Study Group. Am J Epidemiol 1993;137:749-57. 3) Gwiazda J, Scheiman M, Mohindra I, Held R. Astigmatism in children: changes in axis and amount from birth to six years. Invest Ophthalmol Vis Sci 1984;25:88-92. 4) Baldwin WR, Mills D. A longitudinal study of corneal astigmatism and total astigmatism. Am J Optom Physiol Opt 1981;58:206-11. 5) Saw SM, Katz J, Schein OD, et al. Epidemiology of myopia. Epidemiol Rev 1996;18:175-87. 6) Fan DS, Cheung EY, Lai RY, et al. Myopia progression among preschool Chinese children in Hong Kong. Ann Acad Singapore 2004;33:39-43. 7) Ha NR, You JK, Kim JM. Ten-year refractive error and astigmatism changes in Korean subjects. J Korean Ophthalmic Oph Opt Soc 2010;15:389-97. 8) Lin LL, Shih YF, Tsai CB, et al. Epidemiologic study of ocular refraction among schoolchildren in Taiwan in 1995. Optom Vis Sci 1999;76:275-81. 9) Wong L, Coggon D, Cruddas M, Hwang CH. Education, reading, and familial tendency as risk factors for myopia in Hong Kong fishermen. J Epidemiol Community Health 1993;47:50-3. 10) Hirsch MJ. Changes in refractive state after the age of forty-five. Am J Optom Arch Am Acad Optom 1958;35:229-37. 11) Goss DA, Erickson P, Cox VD. Prevalence and pattern of adult myopia progression in a general optometric practice population. Am J Optom Physiol Opt 1985;62:470-7. 12) Kang JE, Jun RM, Lee HJ, et al. Distribution of refractive errors and quantified optometric values in urban elementary fourth graders in Korea. J Korean Ophthalmol Soc 2004;45:1141-9. 13) Kim D. Refraction in young adults. J Korean Ophthalmol Soc 1983;24:711-5. 14) Kim JC, Koo BS. A study of prevailing features and causes of myopia and visual impairment in urban school children. J Korean Ophthalmol Soc 1988;29:165-81. 15) Shimizu N, Nomura H, Ando F, et al. Refractive errors and factors associated with myopia in an adult Japanese population. Jap J Ophthalmol 2003;47:6-12. 16) Wong TY, Foster PJ, Hee J, et al. Prevalence and risk factors for refractive errors in adult Chinese in Singapore. Invest Ophthalmol Vis Sci 2000;41:2486-94. 17) Kang SH, Kim PS, Choi DG. Prevalence of myopia in 19-year-old Korean males: the relationship between the prevalence and education or urbanization. J Korean Ophthalmol Soc 2004;45:2082-7. 18) Lee SJ, Kim JM, Yu BC, et al. Prevalence of myopia in 19-year-old men in Gyeongsangnam-do, Ulsan and Busan in 2002. J Korean Ophthalmol Soc 2009;50:1392-403. 19) Kempen JH, Mitchell P, Lee KE, et al. The prevalence of refractive errors among adults in the United States, Western Europe, and Australia. Arch Ophthalmol 2004;122:495-505. 20) Kleinstein RN, Jones LA, Hullett S, et al. Refractive error and ethnicity in children. Arch Ophthalmol 2003;121:1141-7. 21) Lam CS, Goldschmidt E, Edwards MH. Prevalence of myopia in local and international schools in Hong Kong. Optom Vis Sci 2004;81:317-22. 22) Saw SM, Tong L, Chua WH, et al. Incidence and progression of myopia in Singaporean school children. Invest Ophthalmol Vis Sci 2005;46:51-7. 23) Goss DA, Cox VD. Trends in the change of clinical refractive error in myopes. J Am Optom Assoc 1985;56:608-13. 24) Goss DA, Winkler RL. Progression of myopia in youth: age of cessation. Am J Optom Physiol Opt 1983;60:651-8. 25) Tokoro T, Kabe S. Relation between changes in the ocular refraction and refractive components and development of the myopia. Nippon Ganka Gakkai Zasshi 1964;68:1240-53. 26) Hofman A, Grobbee DE, de Jong PT, van den Ouweland FA. Determinants of disease and disability in the elderly: the Rotterdam Elderly Study. Eur J Epidemiol 1991;7:403-22. 27) Alvarez AA. Light, nearwork, and visual environment risk factors in myopia [electronic theses and dissertations]. [California] University of Berkeley; 2012. 99 p. 28) Wu LJ, You QS, Duan JL, et al. Prevalence and associated factors of myopia in high-school students in Beijing. PLoS One 2015;10(3):e0120764. ecollection 2015. 29) Guo Y, Liu LJ, Xu L, et al. Outdoor activity and myopia among primary students in rural and urban regions of Beijing. Ophthalmology 2013;120:277-83. 63