The iris is the colored part of the eye with the pupil in the middle. The white of your eye is called the sclera; over that, you’ve got a very thin transparent layer called your conjunctiva. This layer often gets inflamed and sometimes infected, resulting in the infection usually described as Apollo (conjunctivitis).

Conjunctivitis will usually lead to sore rather than painful, pink rather than red eye, and you shouldn’t have any problems with your vision, apart from possibly slight blurring which goes away when you blink.

However, there are other things that you do need to look out for. If you get acute pain, especially if it’s red rather than pink, especially if you get any problems with your eyesight, including blurred vision, reduced vision, complete loss of vision, very sensitive to light, or halos around your eyes, those are all medical emergencies and must be dealt with immediately.