It is true to some extent. Because when camera flash works, it can damage people's visual neuroscience and visual cells. However, this kind of damage can be fixed in one or two minutes, which do not do great harm to our eyes. But if you face the camera flash for a long time or the camera flash is too strong, it will hurt your eyes badly. Or your eyes can be damaged without repairing. So for the sake of avoiding it, you should not face the flash too long and close one of your eyes when you use the strong flash.
It is kind of true but you do not have to worry about too much as the damage is small enough to be ignored. Too strong flash will damage eyes as it will stimulate the nerves of eyes and do harm to retina, conjunctiva or cornea. It is the same theory that flash of electric welding is harmful. But camera flash is far from too strong and it is safe. If you think the flash is too close and makes your eyes uncomfortable, you can move it far. There are two situations that camera flash will do harms. One is for infants. Eyes of infants are not fully developed. Too much flash will effect the eye development and cause permanent irreversible harm. The other situation is the flash in a very dark surrounding. Eye pupils are widely open in dark surrounding. When flash come in a sudden, it is easy to get through the eyes and hurt inside nerves. Since you are old enough to bear camera flash, you can take photos as you like and do not do it in dark.
Definitely yes, it could cause damage eyes even cause serious eye problems. As we all known, UV light would harm our eyes, however, the most harmful light is called blue eyes because it could accelerate the the cell oxidation of the macular area of retina to damage eyes. Unfortunately, the camera flash contains blue light. Before taking a photo, there is a large amount of electricity in the camera battery, there would have strong electric current pass the flash light, thus the strong blue light would be emited. It would stimulate eyes if it is too close to. And it cause short-term blind spots to eyes, and the underlying underlying visual cells and optic nerve would be temporary damage. It could be recover in one to two minutes. However, it would be unrecoverable if the flash light is too strong in prolongerd period. The best way to avoid it is not frequently using flash light and do not close to it.