Blue light before bedtime can make it harder to sleep, and the screens on phones, computers and televisions give out plenty of blue light. This is all true. But if you consider blue light as a major problem affecting your sleep or your eye health, it's time to change your mind.
  Philip Yuhas, a professor of optometry（验光）， writes at The Conversation, "Blue light isn't a uniquely technological evil. It's part of sunlight, and your eyes are exposed to plenty of it all the time. You're fine." The pigments （色素） and the lenses of our eyes actually block blue light fairly well-so in a sense, we already have built-in blue-blocking protection.
  Adding more protection isn't likely to help, though. You can buy glasses and screen filters（过滤器） that block blue light, but Yuhas points out they are probably a waste of money. He says,"The products that my patients ask about do not block out much blue light." The leading blue-blocking anti-reflective coating, for example, blocks only about 15% of the blue light that screens give out.
  You could get the same reduction just by holding your phone another inch from your face. Try it now and see if you notice a difference. No？ Then it shouldn't surprise you that a recent analysis concluded that blue-blocking glasses and coatings have no significant effect on sleep quality, comfort at the computer or retinal（视网膜的） health.
  The American Academy of Ophthalmology doesn't recommend blue-blocking products, either. Instead, if you're concerned about your eye health or your ability to get into sleep on time, you already know what to do： Put the screens away at bedtime. Read a book or find something else to do. While you're using screens, take a 20-second break every 20 minutes to look at something 20 feet away. If you get dry eyes when you look at screens for a long time, use artificial tears.



What do we know about blue light？ ______

A. It produces kinds of pigments.
B. It does serious harm to our health.
C. It can be blocked by our eyes effectively.
D. It is a unique product of electronics.

What can be learned about blue-blocking glasses from the text？ ______

A. They are widely popular.
B. They are almost useless.
C. They are inaccessible.
D. They are reliable.

What does the author suggest readers do？ ______

A. Try to wet dry eyes with tears.
B. Keep a distance from blue light.
C. Stop using screens in the evening.
D. Have regular breaks when using screens.

Which of the following would be the best title for the text？ ______

A. Does blue light really affect your health？
B. Are blue-blocking products recommended？
C. Where does blue light actually come from？
D. How can we avoid the harm from blue light？