Children can spend hours a day looking at computer screens and other digital devices. Some eye doctors say this leads to an increase in “computer vision syndrome(电脑视力综合症).”
Nathan Bonilla-Warford is an optometrist（验光师）in Tampa, Florida. He has seen an increase in problems in children. “A lot more children come into the office either because their parents have noticed that they have headaches or red or watery eyes or discomfort, or because their nearsightedness appears to be increasing and they’re worried,” he says.
Dr. Bonilla-Warford says part of the problem is that children may be more likely to pay no attention to early warning signs than adults. “Even if their eyes start to feel uncomfortable or they start to get a headache, they’re less likely to tell their parents, because they don’t want to have the game or the computer or whatever taken away,” he explains.
He says another part of the problem is that people blink（眨眼）less often when they use digital devices. He says, “A person who uses an electronic device blinks about one third as much as we normally do in everyday life. And so that can result in the front part of the eye drying and not staying protected like normal.”
Eye doctors offer suggestions like following which is known as the 20/20/20 rule. That means every twenty minutes look away twenty feet or more for at least twenty seconds from whatever device you’re using.
Other suggestions include putting more distance between you and the device and using good lighting. Of course, another way is to spend less time looking at screens. Many experts say children should spend no more than two hours a day using digital devices—with no screen time for children under two.
But not all eye doctors have noticed an increase in problems in children. Dr. David Hunter, from Children’s Hospital Boston, has not seen an increase in his practice. “While it is possible to develop fatigue looking at screens for a long period of time, there’s certainly no proof that it actually causes any damage（伤害）to the eyes.” he says.
小题1:Which of the following is true according to the passage?
A．Dr. Bonilla-Warford thinks using computers causes nearsightedness.
B．People keep their eyes protected against drying by blinking normally.
C．Children under two can watch TV for less than two hours a day.
D．Dr. David Hunter says headache causes an increase in eye problems.小题2:What does the underlined word “fatigue” mean?
A．Interest
B．Ability
C．Tiredness.
D．Difficulty.小题3:What can be the best title for the passage?
A．Looking at Screen: Two Hours or More
B．How Can Children Use Their Eyes Properly
C．Using Digital Devices: Advantages and Disadvantages
D．How Much Screen Time Is Too Much for Children
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所求的概率为
λe-λxdx=e-λ．
的分解：A=AB十A
．其目的在于将事件分解得便于计算概率的事件，或将复杂事件用较简单的事件表示．