王婧+許迅
摘 要 近年來(lái),隨著近視患病率升高,近視已成為全球性的公共衛(wèi)生問(wèn)題,疾病負(fù)擔(dān)漸重,迫切需要予以防控。越來(lái)越多的研究發(fā)現(xiàn),除遺傳因素外,包括戶外活動(dòng)時(shí)間、近距離工作在內(nèi)的環(huán)境因素也對(duì)近視的發(fā)生和發(fā)展有著潛移默化的影響,而使用一些藥物和器材則可延緩近視的發(fā)生和發(fā)展。本文就近年來(lái)研究較多的與近視發(fā)生和發(fā)展相關(guān)的環(huán)境因素以及防控近視發(fā)生和發(fā)展的方法作一概述。
關(guān)鍵詞 近視 環(huán)境因素 防控
中圖分類(lèi)號(hào):R778.11 文獻(xiàn)標(biāo)識(shí)碼:A 文章編號(hào):1006-1533(2017)23-0003-05
Environmental risk factors for myopia and advances in its control and prevention
WANG Jing, XU Xun*
(Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University; Shanghai Key Laboratory of Ocular Fundus Disease; Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China)
ABSTRACT In recent years, myopia has become a global public health problem with the rapid increase of its prevalence. The costs for the treatment of myopia itself and its complications have made economic challenges to the world. More and more studies have found that environmental factors, such as outdoor time and near-work, play some important roles in the incidence and progression of myopia besides genetic factors, and the use of certain drugs and materials has also been proved to be effective methods for delaying the development of myopia. This article reviews the prevailing view of environmental factors associated with myopia onset and progression as well as the methods for its control and prevention in recent years.
KEY WORDS myopia; environmental factors; prevention and control
近視是眼的一種異常屈光狀態(tài),平行光線在靜止的眼中會(huì)聚焦于視網(wǎng)膜前,從而導(dǎo)致視物模糊[1]。近年來(lái),隨著患病率升高,近視已成為全球性的公共衛(wèi)生問(wèn)題。在包括中國(guó)在內(nèi)的亞洲地區(qū),約69% ~ 90%的人受到近視的影響[2-5]。雖然近視在白種人群中的患病率較亞洲人群低,但在過(guò)去的50年中,白種人群的近視患病率仍然翻了一番[6]。此外,城市環(huán)境下的近視患病風(fēng)險(xiǎn)已遠(yuǎn)遠(yuǎn)高于農(nóng)村環(huán)境[4]。未經(jīng)矯正的近視已成為患者視力喪失的主要原因之一,近視相關(guān)的疾病負(fù)擔(dān)逐漸加重[7-8]。當(dāng)生理性近視(屈光度數(shù)為0 ~ -6.00 D)繼續(xù)進(jìn)展至屈光度數(shù)<-6.00 D且眼軸繼續(xù)延長(zhǎng)并出現(xiàn)其后段結(jié)構(gòu)(鞏膜、視盤(pán)、脈絡(luò)膜、Bruch膜、視網(wǎng)膜色素上皮和神經(jīng)視網(wǎng)膜等)的各種退行性病變時(shí)就進(jìn)入了病理性近視階段。病理性近視會(huì)導(dǎo)致發(fā)生多種嚴(yán)重的眼科并發(fā)癥,包括青光眼、視網(wǎng)膜脫離、近視性黃斑病變、脈絡(luò)膜血管新生、黃斑部或后極部漆樣裂紋、脈絡(luò)膜和視網(wǎng)膜萎縮、視網(wǎng)膜色素變性、黃斑裂孔等,它們具有潛在致盲性,是許多國(guó)家近視人群視力喪失的主要原因之一[1,8-9]。
雖然近視的病因尚未得到完全闡明,但人們普遍認(rèn)為遺傳和環(huán)境因素均對(duì)其的發(fā)生和發(fā)展有一定的影響。就環(huán)境因素而言,戶外活動(dòng)時(shí)間、近距離工作、出生季節(jié)等都已被提出與近視的發(fā)生和發(fā)展相關(guān)。而如何有效阻止近視的發(fā)生和發(fā)展,研究者們也進(jìn)行了多項(xiàng)相關(guān)研究。本文就近視發(fā)生和發(fā)展的環(huán)境影響因素及其近年來(lái)提出的防控方法等作一概要介紹。
1 環(huán)境因素
1.1 戶外活動(dòng)時(shí)間
以前的橫斷面和隊(duì)列研究顯示,澳大利亞、新加坡華人、泰國(guó)和白種人中的兒童近視患病率與戶外活動(dòng)時(shí)間之間存在著顯著的相關(guān)性[10-13]。一項(xiàng)以6 ~ 14歲不同人種兒童為研究對(duì)象的前瞻性研究發(fā)現(xiàn),屈光不正組中的兒童及青少年的戶外活動(dòng)時(shí)間比穩(wěn)定的正視眼對(duì)照組者少1 ~ 2 h(P<0.01)[14]。另一項(xiàng)基于英國(guó)人群的隊(duì)列研究發(fā)現(xiàn),戶外活動(dòng)時(shí)間更多的兒童的近視發(fā)生和發(fā)展風(fēng)險(xiǎn)較低[15]。該研究還指出,雖然戶外活動(dòng)是近視的獨(dú)立影響因素,但“身處戶外”本身對(duì)近視的發(fā)生和發(fā)展起著更重要的作用。澳大利亞的一項(xiàng)以6 ~ 12歲兒童及青少年為研究對(duì)象的隊(duì)列研究也得出了相似的結(jié)論:排除年齡的影響后發(fā)現(xiàn),中低水平戶外暴露者較中高水平戶外暴露者更易罹患近視[16]。
受到流行病學(xué)調(diào)查結(jié)果的啟示,研究者們進(jìn)行了一系列的臨床隨機(jī)、對(duì)照研究。一項(xiàng)在廣州進(jìn)行的前瞻性研究“廣州戶外活動(dòng)縱向研究”(Guangzhou Outdoor Activity Longitudinal Study, GOAL研究)入組了1 789名6 ~ 7歲的中國(guó)兒童,讓實(shí)驗(yàn)組兒童在放學(xué)后額外增加戶外活動(dòng)時(shí)間。這項(xiàng)為期3年的研究發(fā)現(xiàn),在實(shí)驗(yàn)組和對(duì)照組兒童之間,近視的發(fā)生率(分別為30.4%和39.5%, P<0.001)和屈光度數(shù)進(jìn)展(分別為1.42和1.59 D,P=0.04)都有顯著差異,但眼軸延長(zhǎng)(分別為0.95和0.98 mm,P=0.07)的差異沒(méi)有統(tǒng)計(jì)學(xué)意義[17]。另一項(xiàng)基于學(xué)校的前瞻性研究入組了571名7 ~ 11歲的臺(tái)灣兒童,研究結(jié)果與GOAL研究相似:“教室外課間休息”組兒童的近視發(fā)生率較對(duì)照組低(分別為8.4%和17.65%, P=0.001),且屈光度數(shù)進(jìn)展少[分別為(-0.25±0.68)和(-0.39±0.69)D, P=0.02][18]。endprint
上述研究主要采用問(wèn)卷調(diào)查來(lái)統(tǒng)計(jì)戶外活動(dòng)時(shí)間。但問(wèn)卷調(diào)查結(jié)果較為主觀,存在回憶偏倚的可能性很大,且不同研究采用的問(wèn)卷或多或少都存在著一些差別,是一種較為粗糙的統(tǒng)計(jì)方法。如何精確量化戶外活動(dòng)時(shí)間是未來(lái)進(jìn)行此類(lèi)研究所面臨的主要挑戰(zhàn)[13, 19-21]。
1.2 近距離工作
近距離工作一直被認(rèn)為與近視的發(fā)生和發(fā)展密切相關(guān)。一些基于中國(guó)兒童的研究給出了近距離工作與近視發(fā)生和發(fā)展之間的關(guān)系?!氨本﹥和垩芯俊笔且豁?xiàng)以15 666名7 ~ 18歲兒童和青少年為研究對(duì)象的橫斷面研究,其結(jié)果顯示近距離工作時(shí)間較長(zhǎng)且休息時(shí)間較短的兒童的近視發(fā)生率遠(yuǎn)高于兒童近視患病率的平均水平[22]。另一項(xiàng)臺(tái)灣的橫斷面研究入組了5 084名18 ~ 24歲的青年軍人,得出的結(jié)論也是近距離工作時(shí)間越長(zhǎng)、近視度數(shù)越深且眼軸也變得越長(zhǎng)[23]。
不過(guò),有一些研究卻得出了不同的結(jié)論。“北京近視進(jìn)展研究”(Beijing Myopia Progression Study)入組了386名中小學(xué)生,得出的結(jié)論是近距離工作時(shí)間與近視發(fā)生和發(fā)展之間無(wú)相關(guān)性,近視的屈光度數(shù)在不同程度的近距離工作或活動(dòng)者之間并無(wú)顯著差異[24]。入組了多種族人群的“種族與屈光不正的協(xié)同縱向評(píng)估”(Collaborative Longitudinal Evaluation of Ethnicity and Refractive Error)研究則得出了如下結(jié)論:戶外活動(dòng)時(shí)間與近視的發(fā)生之間有相關(guān)性,但近距離工作時(shí)間與近視的發(fā)展之間沒(méi)有關(guān)聯(lián)[25]。此外,一些著名的流行病學(xué)研究如“奧林達(dá)近視縱向研究”(Orinda Longitudinal Study of Myopia)[26]、“新加坡近視危險(xiǎn)因素隊(duì)列”(Singapore Cohort of Risk factors for Myopia)研究[27]和“悉尼近視研究”(Sydney Myopia Study)[28]未得出明確結(jié)論。
近期進(jìn)行的一些研究提示,近距離工作的強(qiáng)度(如長(zhǎng)時(shí)間的連續(xù)<30 cm的近距離工作)或許較近距離工作的總時(shí)長(zhǎng)對(duì)近視的發(fā)生和發(fā)展有著更重要的影響[22,28]。但是,與戶外活動(dòng)時(shí)間一樣,所有近距離工作的時(shí)間也都采用問(wèn)卷調(diào)查得到。因此,如何精確量化近距離工作的時(shí)間及其強(qiáng)度是未來(lái)進(jìn)行相關(guān)研究所必須考慮的重要問(wèn)題。
1.3 其他相關(guān)因素
基于不同年齡人群的橫斷面研究提示,出生季節(jié)以及出生后的光照水平與近視的發(fā)生和發(fā)展之間有相關(guān)性。一項(xiàng)入組了722名1 ~ 3月齡白種人嬰幼兒的橫斷面研究發(fā)現(xiàn),出生于長(zhǎng)和短白晝時(shí)間季節(jié)的嬰幼兒的近視發(fā)生率分別為28.5%和17.5%(P=0.02)[29]。另一項(xiàng)入組了276 911名16 ~ 22歲伊朗人的橫斷面研究也發(fā)現(xiàn),出生于白晝時(shí)間較長(zhǎng)月份者更易發(fā)展為中高度近視患者[30]。一項(xiàng)入組了74 459名18 ~ 100歲英國(guó)人的橫斷面研究亦得出了相似結(jié)論:夏秋季節(jié)出生者罹患高度近視的幾率高于冬季出生者[31]。但中國(guó)的一項(xiàng)研究卻顯示,在排除年齡、性別、父親的受教育程度和出生時(shí)體重等因素影響后,冬季出生兒童的近視發(fā)生率高于其他季節(jié)出生的兒童[32]。
父母的吸煙狀況、特別是母親在懷孕期間的吸煙狀況對(duì)兒童近視的發(fā)生和發(fā)展有一定的影響。一項(xiàng)入組了342名美國(guó)兒童[33]和一項(xiàng)入組了4 164名中國(guó)兒童[34]的橫斷面研究都指出,父母在孕期有香煙接觸史是兒童不罹患近視的保護(hù)因素,但這些兒童更易發(fā)生遠(yuǎn)視。另兩項(xiàng)分別入組了1 334名新加坡華裔兒童[35]和9 970名多種族兒童[36]的研究則僅顯示,父母吸煙是遠(yuǎn)視的危險(xiǎn)因素,與近視發(fā)生和發(fā)展之間的關(guān)聯(lián)不明。
盡管有研究者對(duì)出生季節(jié)和父母吸煙狀況與近視發(fā)生和發(fā)展相關(guān)抱有不同看法,且也有一些橫斷面研究得出了與上述研究不同的結(jié)論[37-38],但這兩種因素的提出拓寬了人們尋找近視發(fā)生和發(fā)展危險(xiǎn)因素的思路。影響近視發(fā)生和發(fā)展的環(huán)境因素可能比我們以前想象的更多,且有些因素的影響已潛移默化地融入了生活之中。近視的發(fā)生或許在人出生時(shí)就受到了某些環(huán)境因素的影響。
2 防控方法
研究者們就如何有效阻止近視的發(fā)生和發(fā)展作了許多嘗試。已有的研究表明,除增加戶外活動(dòng)時(shí)間外,使用低濃度阿托品滴眼液和佩戴角膜塑形鏡(orthokeratology, OK鏡)等對(duì)延緩近視的發(fā)展都有積極的作用。
2.1 低濃度阿托品滴眼液
阿托品是一種非選擇性毒蕈堿拮抗劑,19世紀(jì)時(shí)即被用于近視的治療,許多研究都顯示其低濃度滴眼液在減緩兒童近視進(jìn)展方面有較好的臨床效果。一項(xiàng)臨床隨機(jī)、雙盲、對(duì)照試驗(yàn)“阿托品治療近視”(Atropine for the Treatment of Myopia, ATOM)研究就阿托品滴眼液能否控制近視以及何種濃度的阿托品滴眼液對(duì)近視控制有更好的近期和遠(yuǎn)期效果分階段1和2進(jìn)行了研究。
ATOM1研究證實(shí),2年內(nèi)每晚使用1%阿托品滴眼液可顯著延緩兒童的近視進(jìn)展、減少眼軸延長(zhǎng)[39]:2年后,干預(yù)組和對(duì)照組兒童的屈光度數(shù)進(jìn)展分別為(-0.28±0.92)和(-1.20±0.69)D;對(duì)照組兒童的眼軸平均延長(zhǎng)(0.38±0.38)mm,而干預(yù)組兒童的眼軸長(zhǎng)度無(wú)顯著變化;干預(yù)組屈光度數(shù)<-1.00 D的兒童比例為13.9%,對(duì)照組的這個(gè)比例則高達(dá)63.9%。2年干預(yù)的主要問(wèn)題是阿托品所致瞳孔放大帶來(lái)的近距離視物模糊和畏光,但未對(duì)眼造成嚴(yán)重后果,兒童的最佳矯正視力沒(méi)有下降,眼壓波動(dòng)幅度在5.5 mmHg之內(nèi)且眼壓未超出正常眼壓的上限21 mmHg。
ATOM2研究的受試者是確診為近視的兒童(屈光度數(shù)≤-2.00 D),分組后分別使用0.5%、0.1%和0.01%的阿托品滴眼液,同樣經(jīng)過(guò)2年后觀察不同干預(yù)組間及與對(duì)照組間的效果差異。從兒童屈光度數(shù)的改變和眼軸延長(zhǎng)的具體數(shù)值來(lái)看,阿托品滴眼液的濃度與觀測(cè)指標(biāo)值之間存在著量效關(guān)系,但分析顯示無(wú)統(tǒng)計(jì)學(xué)顯著性,而0.01%阿托品滴眼液對(duì)瞳孔的擴(kuò)大作用微乎其微,可避免由于瞳孔擴(kuò)大帶來(lái)的近距離視物模糊等副作用,被認(rèn)為是較好的控制近視進(jìn)展的阿托品滴眼液濃度[40]。endprint
2.2 OK鏡
OK鏡是一種由透氣性硬質(zhì)材料制成的逆幾何鏡片。近視患者晚上睡覺(jué)時(shí)佩戴OK鏡可使中央部角膜上皮變薄,從而矯正近視,在第2日白天可不需佩戴眼鏡即維持矯正視力。但OK鏡的這種矯正視力作用是可逆的,因此患者每晚都需佩戴。OK鏡不僅可以起到一過(guò)性“治療”近視的作用,在控制近視進(jìn)展上也有一定的效果。研究者們進(jìn)行的為期1個(gè)月[40]、6個(gè)月[41-42]、1年[42]、2年[41,43-47]和5年[48]的臨床研究都得出了相似的結(jié)論:OK鏡可有效延緩近視的進(jìn)展。
雖然一些研究都發(fā)現(xiàn),即使佩戴OK鏡,近視患者的眼軸也會(huì)隨時(shí)間有所延長(zhǎng),但與對(duì)照組相比,佩戴OK鏡確可減慢近視進(jìn)展和眼軸延長(zhǎng)的速率[44-47]。此外,與阿托品滴眼液不同,OK鏡可用于屈光度數(shù)<-6.00 D的患者。不得不說(shuō),OK鏡的出現(xiàn)是近視患者的福音,但其價(jià)格較貴。另外,2001年后報(bào)告了100多例與佩戴OK鏡相關(guān)的微生物角膜炎[49],這也讓一些近視患者對(duì)選用OK鏡產(chǎn)生了顧慮。
3 結(jié)語(yǔ)
近年來(lái),隨著近視患病率升高,其已逐漸成為一個(gè)全球化的公共衛(wèi)生問(wèn)題。除了不可改變的遺傳因素外,研究者們正將視線越來(lái)越多地聚焦在環(huán)境因素上,試圖找到阻止近視發(fā)生和延緩近視進(jìn)展的方法。對(duì)戶外活動(dòng)時(shí)間、出生時(shí)的光照時(shí)間和父母吸煙狀況與近視發(fā)生和發(fā)展之間關(guān)聯(lián)的研究提示,環(huán)境因素對(duì)近視的發(fā)生和發(fā)展有潛移默化的影響,因此強(qiáng)制性地增加兒童及青少年的戶外活動(dòng)時(shí)間可能成為未來(lái)防控近視的有效措施。此外,相關(guān)研究已證實(shí),低濃度阿托品滴眼液對(duì)近視發(fā)生有“防患于未然”的作用,OK鏡可延緩近視進(jìn)展。人類(lèi)對(duì)近視的防控已經(jīng)不再“力不從心”。
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