Yes, reading in the sun is bad for your eyes. When you are reading in the sun, your pupil will last contracting and that leads to exhaustion of your eye muscle, distending pain of your eyeballs. It is reported that if you read books in the sun for a very long time, your eyes will become too tried to recover and at last, your eyesight will decline, your retina will be damaged and your sensitivity of vision will decline as well. All of these injuries may not be repaired any longer. What's more, when you read in the sun, you may have great chance to hurt your cornea and crystalline lens. So stop reading in the sun in the sake of your eyes. Avoiding reading in the bright light such as sunshine is your best choice. When you have outside activities in the sun, you should wear a pair of black sunglasses to protect your eyes. When your eyes feel tried, you should stop to have a break and look views outside
Technically, if the sun is not too bright, it is Ok to reading in the sun. But you shall not staring directly at the sunshine which will make you difficult to open your eyes. If the light is too bright, you shall try to shield your eyes with a pair of sunglasses. They can help your reduce the intensive light, reduce glares as well we prevent glares etc.
Of course, reading in the sun will do harm on your eyes. When you read outside, the words on the book will be reflected by the strong sunlight into your eyes which may intense your visual corneal and stimulate the eye nerves. This doing will make your eyes feel tired easily. If you go on doing this, your eyes will feel discomfortable when changing into the dark situation. What's worse, you will get short sighted. If you already have the prescription, you will have higher prescription. You'd better stop doing this.
It's obvious that reading in the sun will be very harmful for your eyes. There are a lot of ultraviolet rays in the strong sunshine.And human eyes are very vulnerable to ultraviolet rays damage,especially in extremely delicate parts. The long-term damage by the ultraviolet light will lead to keratitis, macula lutea damage
The harmful ultraviolet light is eye health killer, ultraviolet long-term damage, still can lead keratitis, and even the damage of macula lutea.