2. Bacteria
Bacterial pinkeye may not change the color of the eye at all, but it is often accompanied by a thick yellowish or greenish discharge. The bacteria may also create crusts on the eye when the discharge dries.
There are a number of types of bacteria that cause this condition, and it is more common among children than adults.
In fact, it is a leading cause of children missing school, and the bacteria are often present in kindergartens and primary schools.
For this reason, children should be taught to wash their hands frequently and to avoid touching their fingers to their eyes.