People with poor eye hygiene and contact lens abusers (e.g. those who wear contact lenses overnight) are at an increased risk of developing corneal ulcers. Corneal ulcers are a common condition in humans, particularly those living in the tropics and in agrarian societies. In developing countries, children afflicted by vitamin A deficiency are at a high risk for corneal ulcer and may become blind in both eyes, which may persist lifelong if not treated.