Red eyes are common and can be due to several things. For example, it may be due to inflammation or superficial bleeding in the eye. Usually, the trouble goes away by itself but sometimes you may need treatment.
Here you can read more about irritated eyes, such as eye inflammation, blur of the eye, eye damage by bright light, Sjögren’s syndrome and red eyes.
Sjogren's syndrome is a disease that mainly means that you become very dry in the eyes and mouth. It is an autoimmune disease, which means that the immune system attacks its own tissue. The disease persists throughout life, but there are treatments that relieve the hassle.
Your eyes can be damaged by bright light. For example, if the sun is shining brightly on snow, sea or white sand. It's called being snow blind. The eyes can also be damaged if you look directly at a welding flame. Then it is called a welding glare. The trouble usually goes by itself.