Infections can be connected to the cornea (cornea) observed non-infectious inflammation, ulceration, mechanical damage and environment-related injuries. An infection (keratitis) often occurs with a secondary conjunctivitis and can be caused by viruses, bacteria, Acanthamoeba, or fungi. Ulceration is usually an expression of a progressive keratitis. Symptoms rather suggest a corneal involvement than a simple conjunctivitis include pain, especially when exposed to light, and decreased visual acuity. To assess the corneal microbiological processes are sometimes required in addition to the slit lamp examination. Tips and risks Perform a slit lamp examination and fluorescein staining when patients have a painful red eye, a foreign body sensation and / or a reduced visual acuity.