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Myopia



The fact that around one in four people around the world suffer from myopia has resulted in a lot of research being done into the causes and development of this eye disease. Despite all the theories, there have been no conclusive answers, which means a quarter of the population still live with the inconvenience and hassle of wearing glasses or contact lenses to correct their vision impairment. So what do we know
Myopia, also known as nearsightedness or shortsightedness, results from the resting eye focussing on objects in the distance. For the eye to look at objects close to the subject, the lens must increase in thickness and in the radius of curvature. Subjects with this condition often have excessively long eyes which results in the image forming in front of the retina as opposed to on it. The main culprit of this deformation impairment is excessive postnatal eye growth. Although some cases arise in early adulthood, the majority are formed in the early school years. Around 5% of cases lead to blindness and it predisposes shortsighted people to retinal detachment, retinal degeneration and glaucoma.
As mentioned earlier, who is actually prone to this illness has not yet been fully determined. However, those more likely to develop the impairment are children with myopic parents or those doing ’near work’. If you suffered childhood illnesses, low birth weight, used night lights as a child or have nearsighted siblings, you may also be more susceptible to the condition. Thus it can be seen that researchers are divided as to whether the disease is caused by genetic or environmental factors. There are two main points supporting the genetic argument. Firstly, there is evidence to suggest that myopia may be due to a dominant gene that is inherited by the child from the parents. Secondly, it is also thought that myopia may be caused by influences from the nervous system that are not normal and have a negative impact on the developing eye. Although there is ample evidence to support the fact that myopia runs in families, this evidence has not been directly linked as a definite cause for the disease’s development. Moreover, this is not to say that the case for environmental factors shows no validity.
Researchers have split environmental factors up into two main contributors. One is that too much ’close work’ is attributed to the development of myopia. The other is a theory which states that night lights may be responsible for myopia in infants. For the former, experiments have been conducted on both monkeys and chicks to prove its validity. They were forced to view objects at a close distance. By limiting their visual field, there were definite and extreme changes in their ocular refraction which led to the animals becoming myopic. For the latter, tests conducted on infants concluded that those who were exposed to a night light had a greater tendency to develop myopia. In fact, the more light they were exposed to, the more prevalent nearsightedness became.
However, much more study is needed to verify the results of this research on night lights. There are still some question marks over the tests’ validity. Some believe that myopic parents are more likely to light the rooms of their children, making it a genetic and not an environmental factor. Some have suggested that research hasn’t been extended to all ethnic groups, especially Asians in whom the incidence of myopia tends to be higher. Others have asked how an infant’s eye carl recall the damage it received earlier in life when the impairment doesn’t manifest itself till later in life. Finally the research is also reliant on parents’ recollection of their child’s earlier childhood events being accurate. This essentially means that you do not need to go and start throwing out your children’s night lights just yet.
With the lack of concrete evidence on how myopia is caused, it is hard to determine a way of preventing the condition. Cures are available to some. The most popular is probably Lasik eye treatment. This is where lasers are used to correct one’s vision. However, this is not a miracle cure as it can have side effects and even be quite dangerous for some. So for now around 25% of the population continues to power on through challenges with their glasses or contact lenses regardless of how it may affect their lifestyle.

答案

参考答案:accurate

单项选择题
单项选择题

二、阅读以下文字,完成以下问题。

1988年,一位爱好飞蛾的美国医生发表了一篇科学论文,论述了夜晚的灯光是如何影响飞蛾的。这是一篇很普通的文章,但在当时,这也是一篇最明确地指出人造光会对动物产生危害的文章,一些针对人造光与动物关系的研究由此产生了。

在美国的佛罗里达海岸,城市的灯光曾造成刚破壳而出的小海龟迷路,使一些小海龟忽然爬向错误的方向,引导小海龟踏上了死亡之途。在很多场合下,即使动物们不直接暴露于灯光之下,它们也难以摆脱光污染的伤害,城区里的灯光会通过云层反射下来,使夜空处在非自然的光亮下,科学家们称这种情形为天空赤热。

最早指出天空赤热危害的是天文学家,因为这种光现象极大阻碍了他们对星空的观测。佛罗里达的科学家迈克尔·萨曼认为,钠灯也许可以成为城市的新光源。钠灯释放一种特殊的黄色波长,天文观测时,这种光波对观测的影响相对较小,而且对海龟和飞蛾之类的动物也不会造成伤害。萨曼说,海龟也许根本看不见钠灯,即使看见了,这种频率的光波也不会对它们的方向判断造成混乱。

然而,钠灯并不是万用良方。对于有些动物而言,钠灯的黄色光波和其他灯光的光波并无差异,有时甚至比传统的灯光显得更糟。突然暴露于灯光中的青蛙会延缓它们的进食和生殖行为,在黄光和红光下,火蜥蜴甚至无法从一个地方移动到另一个地方。灯光的照射使水生无脊椎动物在夜间的活动量减少,其后果就是减少了这些无脊椎动物对藻类的消耗,造成藻类的恶性繁殖,水质下降。灯光还可能对鸟类的磁场定位系统造成扰乱,使这些鸟儿时常迷失在电视塔的附近。灯光可以削弱飞蛾的防御反应,使飞蛾在遇到危险时失去逃跑能力。

[ ]是那些有能力适应人造光的动物,它们在进化的过程中也不得不付出生物学的代价:某些异常的品质受到奖赏,[ ]在正常的自然状态下,它们[ ]变得不适应了。从逻辑上说,这样的进化选择将导致动物渐渐适应永恒的光照环境,并进化一些新的品质,它明显不同于在黑暗环境中生存的野生动物。假若让正常状态下和非正常状态下的这种动物交配繁衍,那将给这种动物带来灭绝的危险。

也许,我们的确到了找回那片失落星空的时候了。

根据文意,第五自然段中[]的连词,依次是()。

A.虽然,至于,也

B.除非,或许,仍然

C.尽管,不过,反而

D.即使,而,却