Many people think of sunglasses as a stylish fashion accessory in the summer, and they would probably answer this question with “yes, of course!” In fact, they're right. Sunglasses are an important way to keep your eyes healthy, as they will protect your eyes from bright light and harmful UV radiation from the sun. You should absolutely keep a pair of sunglasses around, and if you wear glasses, you should acquire a pair of prescription sunglasses.
Many people wear sunglasses in the summer because they work to protect the eyes from bright light and glare. Skiers also like to wear sunglasses and goggles out on the slopes, since the glare from snow can get quite strong. However, it's also important to wear sunglasses even when it's not bright out, since UV radiation can still filter through clouds and fog. You may want to consider getting two pairs: one pair with darkly tinted lenses for summer use, and a pair with more mild tinting which still retains UV protection for the winter.
Cataracts, macular degeneration, and skin cancers around the eyes have all been linked to UV exposure. These conditions can lead to eventual blindness if they are not addressed, and they can still be painful and expensive to treat. It's much better to simply wear sunglasses and protect your eyes. You can also, of course, look stylish in the process.
Sunglasses are especially important for people who are taking medications which increase sensitivity to light. Your doctor should tell you if a drug will make you more light-sensitive, and he or she may recommend sunglasses for comfort and eye protection. Children should also wear sunglasses, since their eyes are also very vulnerable to UV radiation. According to Prevent Blindness America, children's eyes do not have the more developed UV protection that adults' eyes do.
You should take some time when picking out sunglasses. Find a pair which are comfortable and which fit well with your personal aesthetic, but also look for glasses which will filter out at least 99% of UV-A and UV-B rays. Try to find sunglasses which will not distort color, as well, since this will keep you more comfortable as you navigate the world. Avoid small sunglasses which do not completely protect your eyes and the surrounding skin, and remember not to wear sunglasses at night, especially when you are driving.