There’s a reason why so many people rely on a morning cup of coffee: It can help you feel awake. But sometimes it may cause less desirable side effects like caffeine-induced(咖啡因引起的) vision disturbances. Here are the reasons why caffeine can affect vision, plus how to prevent these eyesight issues.

1. You Drank Too Much Caffeine

Can too much caffeine cause blurry(模糊的) vision?      ▲       Eating or drinking a moderate amount of caffeine (which, according to the Mayo Clinic, is up to 400 milligrams per day, or the caffeine in about four cups of coffee) can help you feel more awake with little to no additional symptoms, according to the University of Michigan. And while moderate caffeine intake isn’t bad for your eyes, consuming large amounts of caffeine may lead to side effects like — you guessed it — blurred vision.

The fix:​Stick to moderate or low doses to avoid a caffeine vision disturbance, according to the University of Michigan.

2. Caffeine Affects Your Blood Sugar

Even moderate doses of caffeine can cause your blood sugar to rise or fall, particularly if you have diabetes(糖尿病), according to the Mayo Clinic. And shaky eyesight can be a side effect of these blood sugar fluctuations(波动), according to the Cleveland Clinic.

The fix: If caffeine regularly causes blood sugar swings and resulting vision disturbances, limit how much of the substance you drink, according to the Mayo Clinic. If you have diabetes, talk to your doctor about the best sources and dose of caffeine for you.

3. Heavy Caffeine Use May Contribute to Glaucoma(青光眼)

Research suggests long-term, heavy caffeine usage may contribute to blurry vision down the line. For instance, consuming large amounts of caffeine every day may increase your risk for glaucoma — a group of eye conditions that causes gradual vision loss in some cases.

The fix:​ Get regular eye exams to take care of your vision health, according to the Mayo Clinic. You can also talk to your eye doctor about whether to limit caffeine based on your eye pressure.

1.Who may be interested in this text?

A Eye doctors.

B Coffee makers.

C Technology fans.

D Coffee lovers.

解析：选D。D推理判断题。本文主要讲了喝咖啡对视力产生的影响和原因，由此推断，咖啡爱好者可能会对本文感兴趣。故选D。

2.What can be put back into the blank?

A Nobody knows exactly.

B The short answer is yes.

C It’s hard to say.

D Maybe it’s unclear.

解析：选B。B推理判断题。根据前面的问题“Can too much caffeine cause blurry vision?”和后面的“consuming large amounts of caffeine may lead to side effects like — you guessed it — blurred vision”可知，摄入大量咖啡因可能会产生副作用，比如视力模糊，因此答案是肯定的。故选B。

3.What is the writer’s advice to coffee fans with diabetes?

A To give up coffee.

B To find other hobbies.

C To talk to doctors.

D To drink more.

解析：选C。C细节理解题。根据第五段最后一句“If you have diabetes, talk to your doctor about the best sources and dose of caffeine for you.”可知，如果你患有糖尿病又喜欢喝咖啡，可以向医生咨询咖啡的最佳来源和剂量。故选C。

4.What is the best title for the text?

A Reasons Why Caffeine Can Affect Your Vision.

B How Many Cups of Coffee Can You Drink a Day?

C Ways to Prevent Serious Eyesight Issues.

D How Does Caffeine Affect Your Digestive System?

解析：选A。A主旨大意题。根据全文内容可知，本文主要向我们介绍了三个咖啡损伤视力的原因。故选A。