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抽煙與眼疾 Smoking and eye diseases


王司宏

執筆/
書田眼科主任醫師 王司宏

眾所周知,「吸煙過量有害健康」,抽煙不但會影響呼吸及心臟血管功能,導致慢性阻塞性肺病及心肌梗塞等心肺疾病外,抽煙也與某些惡性腫瘤有關,但停止抽煙十年以後,發生惡性腫瘤的危險性可以降低百分之五十。抽煙會不會影響眼睛的視覺功能呢?有越來越多的流行病學資料顯示,抽煙與眼疾有關,而且與抽煙有關連的眼疾種類也逐漸增加。與其他抽煙導致的疾病類似,抽煙對眼睛的影響與劑量有關,累積劑量越大,產生的眼疾越嚴重。

煙草所產生的煙霧中含有超過四千種的活性成份,其中有四十種以上是會致癌的,這些成份在急性接觸或是長期曝露下都有毒性,其中也包括了對眼睛的傷害。那些眼疾與抽煙有關呢?抽煙又會加重那些眼疾的程度及進展呢?這可以先從眼球表面的結膜談起。結膜對煙草所產生的煙霧相當敏感,所以受到刺激容易產生結膜充血及流淚的現象,而這些煙霧中的化學物質也會刺激結膜上的神經末端,導致灼熱、刺痛等極不舒服的感覺。另外,長期曝露在煙草的塵埃粉末中(如在煙草工廠工作),可能導致眼睛黏膜的惡性變化。

抽煙是引起大部份缺血性眼疾的一個極重要的危險因子,抽煙對眼睛的血液循環有不利的影響,有實驗指出抽煙會增加眼球脈絡膜血管的阻力,也會降低眼動脈的血流速度。而頸動脈的動脈粥樣硬化斑有時會導致眼動脈暫時或永久的栓塞,產生暫時性黑矇(失明)或視網膜永久的梗塞(俗稱眼中風),臨床證實上述現象出現在老年人口與抽煙有強烈相關。

在供應視神經乳頭的血管如發生收縮或梗塞,會使得視神經得不到養份供給,導致缺血性的視神經病變,產生急性無痛性的視力喪失,有許多研究指出抽煙是導致此症的重要危險因子。此外不明原因的眼肌麻痺導因於供應眼外肌血流減少,使得這些肌肉產生功能性的癱瘓,抽煙已被證實是一危險因子。

老年性黃斑部病變是西方國家中造成視力喪失的主因之一,據估計75歲以上的人口有30%有早期病變,而7%有晚期病變。在此病症的早期視力是正常的,而隨著病變的進展,黃斑部功能受影響,視力會嚴重受損,老年性黃斑部病變的致病原因尚不十分清楚,心臟血管疾病、飲食及長時間陽光曝曬,都被認為與此症的發生及進展有關。

有許多的研究證實抽煙是此病症進展的重要危險因子之一,抽煙者(尤其是每天超過1包)比不抽煙者有2-2.5倍產生此症的危險。抽煙會影響眼球脈絡膜的血流,造成缺血、缺氧及微小血管的梗塞,這些會使得需要充沛血流供應的黃斑部易受傷害,可能易導致黃斑部病變的進展。

白內障是世界上造成失明及視力障礙主因,據估計全世界有超過壹仟伍佰萬人因白內障而失明。隨著人們平均壽命的增長,因白內障導致的視覺障礙也逐漸增加。有許多研究指出抽煙與白內障的進展有明顯相關,在不同的白內障型態中,核性硬化是與抽煙最有相關的。抽煙會導致白內障的形成,與抽煙影響水晶體內氧化及抗氧化狀態有關。

氧化傷害是白內障生成的主因。許多研究都顯示抗氧化劑(如核黃素,維生素C&E,類葫蘿蔔素),可以預防白內障,白內障導因於水晶體的老化使得抗氧化劑及抗氧化酵素減少,抽煙會加重這個現象,此外煙草中含有許多重金屬(如鎘、銅、鉛)會堆積在水晶體上,造成更多傷害。

凸眼性甲狀腺腫(Graves眼疾)是因自體免疫導致甲狀腺病變,真正的致病因並不清楚,雖然遺傳基因及環境因素均與此症之發生有關,抽煙可能在帶有致病基因的個体引起此病。在各種不同的臨床表現中,眼睛的症狀與抽煙最有關連,且有抽煙者比不抽煙者症狀更嚴重。

菸中毒性弱視,在以往物質缺乏營養不良的年代最常見,近年已不常見,患者多為中年男性,有長期抽煙及酗酒的習慣,症狀有兩側視力障礙,視野在盲點至中心注視部位有暗點,且有色覺異常。雖然到底是抽煙本身,還是加上酗酒才是致病的主因仍有爭議,事實上,此病的發生是長期營養不良的後遺症,導致維生素B群代謝不良,造成了視神經的傷害。治療之道,除了戒煙戒酒補充養份外,還要給予大量維生素B。

抽煙與青光眼之間的關係仍有爭議,有些研究指出抽煙是青光眼的危險因子,不過有更多的研究顯示兩者並沒有相關,所以到目前為止,仍傾向抽煙與青光眼無關。

抽煙在糖尿病視網膜病變中的角色並沒有清楚的定位,近來的報告顯示抽煙對糖尿病視網膜病變的產生及進展僅有極少關連或完全不相關。

抽煙不僅影響個人,甚至會傷到下一代的眼睛,研究顯示母親在懷孕期間有抽煙習慣者,則所生的嬰兒比一般嬰兒有更多產生『斜視』的危險性,尤其是嬰兒體重少於2500公克,此斜視的危險性更高,如果母親在懷孕期間戒煙,則危險性與一般孕婦差不多。

抽煙對眼睛的傷害正逐漸增加,尤其是白內障與老年性黃斑部病變,這兩種造成視力喪失及失明的眼疾,與抽煙有關。要減少這些不必要的傷害,唯一的方法就是戒煙及禁煙,個人拒絕抽煙,公共場所及密閉空間(尤其有中央空調或冷氣間)禁止抽煙。拒絕煙害,除了有益身體健康,也有助眼睛的健康及明亮。

It is well known that over smoking will impair health. Smoking will influence respiratory and cardiovascular functions and lead to cardiovascular diseases such as chronic obstructive pulmonary disease and myocardial infarction. In addition, smoking is related to some malignant tumors. The risk of malignant tumors decreases 50 percent after quitting smoking for ten years. Will smoking influence visual functions of eyes? There is growing epidemic data showing that smoking is related to eye diseases. The number of eye diseases related to smoking is also increasing. Similar to other diseases caused by smoking, eye influences caused by smoking are related to dose. The greater the accumulated dose, the more severe the eye disease.

There are over 4,000 active ingredients in the smoke resulting from tobacco. In which, over 40 active ingredients will result in tumor. Acute contact or chronic exposure under these ingredients will be toxic, including eye damages. What eye diseases are related to smoking? Which kind of eye diseases’ level and progress are influenced by smoking? It can be discussed from conjunctiva on the surface of eyeball. Conjunctiva is very sensitive to the tobacco smoke; therefore it is easily to have conjunctival hyperemia and tearing when it is stimulated. Chemicals in the smoke will stimulate nerve terminals of conjunctiva and lead to very uncomfortable sensation such as burning and stinging. In addition, long term exposure under tobacco powders (e.g. working in tobacco factory) might lead to vicious changes of ocular conjunctiva.

Smoking is a very important risk factor of most ischemic eye diseases. Smoking has adverse effect on ocular blood circulation. There is experiment indicating that smoking will increase resistance of ocular choroid vessels and also decrease blood flow rate of ocular arteries. Carotid atherosclerotic plaque sometimes leads to temporarily or permanent embolism of ocular arteries and leads to temporarily amaurosis fugax (blindness) or permanent infarction of retina (It is so called “eye stroke”). It is proved clinically that above phenomena are strongly related to smoking when occur in elderly population.

If there is constricted or infarction in vessels supporting optic papilla, ocular nerves will have no nutrients and lead to ischemic optic neuropathy and result in acute painless vision loss. Many researches indicate that smoking is an important risk factor of this disease. In addition, ophthalmoplegia resulting from unknown reason is caused by extra-ocular muscles’ blood flow decrease therefore lead to functional paralysis of these muscles. Smoking is proved to be a risk factor of this disease.

Age-related macular degeneration is one of the major causes for vision loss in western countries. It is estimated that there are 30% with early degeneration and 7% with late stage degeneration in over 75-year-old population. The vision is normal in the early stage of this disease, but the macula function will be affected with the progress of the degeneration afterward and vision will be damaged seriously. The causes of age-related macular degeneration are not clear now. Cardiovascular diseases, diet and long-term sunlight exposure are thought to be related to progress of this disease.

Many researches demonstrated that smoking is one of the important risk factors of the age-related macular degeneration progress. Risk of having this disease for smokers (especially who smoke over 1 package per day) is 2-2.5 fold higher than non-smokers. Smoking will affect blood flow of ocular choroid and lead to ischemic, hypoxia and micro-vessel infarction. These will make macula vulnerable because macula needs abundant blood supply and might lead to progress of macular degeneration.

Cataract is a major cause of blindness and visual impairment worldwide. It is estimated that there are over 15 million people are blind due to cataract. With longer life expectancy, there are more visual impairment due to cataract. Many researches indicated that smoking is obviously related to cataract progress. In different types of cataract, nuclear sclerosis is most strongly related to smoking. Smoking will lead to cataract formation because smoking will affect oxidative and anti-oxidative status of crystalline lens.

Oxidative damage is a major cause of cataract formation. Many researches demonstrated that antioxidants (e.g. riboflavin, vitamins C&E, carotenoid) can prevent cataract. Cataract results from the aging of crystalline lens because it decreases antioxidants and anti-oxidant enzymes. Smoking will exacerbate this phenomenon. In addition, tobacco contains lots of heavy metals (e.g. Cadmium, Copper, Lead) that will accumulate in lens and result in more damages.

Exophthalmos goiter (Graves’ eye disease) results from autoimmune which leads to thyroid pathological changes. Although gene and environmental factors are related to this disease, the real causes are not clear. Smoking might induce this disease in people who carry pathogenic gene. In different clinical performances, eye situation is most closely related to smoking and smokers will have more severe disease than non-smokers.

Smoking amblyopia was commonly seen in the age of lacking materials and nutrition; it is not as common in recent years. Patients mostly are middle-aged male with long term smoking and alcoholism habits. The symptoms are bi-lateral vision impairment, dark point in blind point to central gaze in the field of vision and abnormal color vision. There is still disputation between whether smoking or smoking plus alcoholism is major pathogenic cause. In fact, this disease is a sequel of long term malnutrition which leads to vitamin B metabolic disorder and optic nerve damage. The treatment way is to give abundant vitamin B in addition to quit smoking and alcohol and supply nutrients.

There is still disputation whether smoking is related to glaucoma. Some researches indicated that smoking is a risk factor of glaucoma but more researches demonstrated that there is no relationship between both. Therefore it tends to think that glaucoma is not related to smoking so far.

The role that smoking plays in diabetes retinopathy is not clear. Recent reports indicated that smoking is less or not related to the production and progress of retinopathy.

Smoking not only affects individuals but also damage the eyes of next generation. Researches demonstrated that if the mother has smoking habits during pregnancy period, her baby will have higher risk to have strabismus than general babies. In particular when baby’s body weight is less than 2500g, the risk of strabismus is even higher. If the mother quit smoking during pregnancy period, the risk is similar to general pregnant women.

Eye damages result from smoking are increasing now, especially cataract and age-related macular degeneration. These two diseases lead to vision loss and blindness are related to smoking. To decrease these unnecessary damages, the only way is to quit smoking and ban smoking. Reject individually smoking and ban smoking in public area and closed space (space with central air conditioning or air-conditioned room in particular). Rejecting smoking is not only beneficial to body health but also helpful for eye health and brightness.


最後更新日期:2018/12/20 上午 12:00:00
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