Conjunctivitus

The Conjunctivitis Curse is a defensive curse that causes great pain to the victim's eyes.

Known Uses and Mentions
It was mentioned in a letter from Sirius Blackin Goblet of Fire as a suggestion to Harry. It was actually used by Viktor Krum in the first task of the Triwizard Tournament. It was also used by Olympe Maxime on giants in 1995.

Etymology
The name "Conjunctivitis" could come from the disease of the same name, also known as "pink eye" or "caterpillar eye", due to its symptom of scabby inflammation.