There is pupil in our eyes to adjust the light our eyes received to protect our vulnerable eye nerve.You can observe the changes of pupil with a mirror and a lamp.You may find the little dark point in the center of your eyes will turn smaller when you turn the light on and it will recover when you turn the light off.
But when we turn to expose to a strong light,the pupil can not adjust quickly enough or it is beyond the range of adjustment which will let the strong light in your eyes directly and hurt your eye nerve.That is why we should not see sun with naked eyes and someone gets blind by seeing the light from electic welding without any protection. As someone can be very sensitive to light changes, you should avoid being under strong light to protect your retina from injury.