近视

title: 患者分布.
content: 近视是现时其中一个最常见的已知疾病。全球各地都会有人患上近视,但患者以亚洲人占较多数。当中又以香港、台湾、韩国人为主。其次为日本、新加坡、澳门等。  而现时欧美国家患上近视的人亦越来越多。
title: 近视的预防.
content: 预防近视(非遗传性近视)是许多学生除学习之外的首要事务之一,但是如何才能预防近视却是一个有争议的话题。这一方面是因为近视形成的过程与原因较为复杂,医学上对其具体的生物学过程还没有透彻的认识。近视的预防是可行的,至少可减缓加深的速度。其主要方法是既包括良好的用眼习惯的培养。  要预防近视,一定要自小做起,由幼儿时期开始便要让儿童有正确的阅读及用眼习惯,令发育期中的眼睛不要受到大的不良刺激。即使成年人也要留意这几方面,以减慢视力衰退的速度。事实上,配戴凹透镜便能矫正因近视导致的模糊视力,其问题是在于儿童近视是会因应眼球成长而不断加深,深近视度数(600度或以上)已被证实会增加患不同眼疾(例如: 青光眼、白内障和视网膜脱落)的风险,所以控制儿童近视不断快速地加深是必需的。
title: 理解近视成因对预防近视的重要意义.
content: 自己理解近视的成因对于预防近视是很重要的。由于商业利益的影响,人们从眼科医生、眼镜店与互联网上得到关于对待近视的方法并不一定都是正确的(当然也可能是正确的)。只有自己深刻理解了近视的成因,才能从科学的角度辨明事实的真相,并在日常生活中注意从多方面保护自己的眼睛,预防近视。
title: 户外活动.
content: 多参加户外活动,例如散步等。有研究表明,青少年户外活动的时间与近视加深速度成反比。
title: 控制儿童近视加深的方法.
content: 目前控制儿童近视加深的方法主要有以下三种:
title: 近视的遗传基因.
content: 至今,人们已经定位了一些可能诱发近视眼的基因位点,收入《人类孟德尔遗传》中,下表列出了这些基因:
title: 治疗.
content: 但须注意,假性近视可以经由点散瞳剂等等可以根治;真性近视即使戴普通眼镜、隐形眼镜或视力矫正手术达到正常视力,依旧无法根治。

Summary: 近视(英语:Near-sightedness, 或称 myopia, 或称 short-sightedness),系指眼睛视觉成像未能聚焦于视网膜上,而是聚焦于视网膜之前的情形。患者在目视远物会模糊,而视近物相对清楚。其他症状包含头痛跟眼睛疲劳,严重的近视会增加视网膜剥离、白内障及青光眼的风险。 目前相信潜在肇因来自遗传与环境因素,风险因子为做事时需聚焦于近物、长时间待在室内及家族病史等,近视也和高社经地位相关, 其他因素包括营养不良等。潜在的构造问题是眼球直径过长,或水晶体太缺乏弹性,但后者较少见。近视是一种眼屈光不正,确诊方式是做视力测试。 目前已有实验性的例证指出,尽量让儿童待在户外可预防儿童近视,有可能是因为他们接触到自然光。近视可经由配戴眼镜、隐形眼镜或接受手术来矫正。配戴眼镜是最简单也最安全的;隐形眼镜则可以提供较宽阔的视野,但也伴随着感染的风险;而接受屈光手术可以永久改变眼角膜的形状。 近视是最常见的眼睛问题,据估计约有 15 亿人患有近视(约占全球人口 22%),不同地区的近视人口比例差距甚大,约占成人的 15~49%,男女比例倒是相去无几。近视的儿童在尼泊尔乡间仅占 1.2%,在南非占 4%,在美国占 12%,但却在中国部分大城市却高达 37%。自 1950 年代起,近视人口比例持续增加。近视却未经矫正是视力丧失的常见原因,放诸四海皆准,其他原因包含白内障、黄斑部退化以及缺乏维他命 A。

Near-sightedness: Near-sightedness, also known as short-sightedness and myopia, is an eye disorder where light focuses in front of, instead of on, the retina. This causes distant objects to be blurry while close objects appear normal. Other symptoms may include headaches and eye strain. Severe near-sightedness is associated with an increased risk of retinal detachment, cataracts, and glaucoma. The underlying cause is believed to be a combination of genetic and environmental factors. Risk factors include doing work that involves focusing on close objects, greater time spent indoors, and a family history of the condition. It is also associated with a high socioeconomic class. The underlying mechanism involves the length of the eyeball growing too long or less commonly the lens being too strong. It is a type of refractive error. Diagnosis is by eye examination. Tentative evidence indicates that the risk of near-sightedness can be decreased by having young children spend more time outside. This may be related to natural light exposure. Near-sightedness can be corrected with eyeglasses, contact lenses, or surgery. Eyeglasses are the easiest and safest method of correction. Contact lenses can provide a wider field of vision, but are associated with a risk of infection. Refractive surgery permanently changes the shape of the cornea. Near-sightedness is the most common eye problem and is estimated to affect 1.5 billion people (22% of the population). Rates vary significantly in different areas of the world. Rates among adults are between 15% to 49%. Rates are similar in females and males. Among children, it affects 1% of rural Nepalese, 4% of South Africans, 12% of Americans, and 37% in some large Chinese cities. Rates have increased since the 1950s. Uncorrected near-sightedness is one of the most common causes of vision impairment globally along with cataracts, macular degeneration, and vitamin A deficiency.