What is the most common cause of a corneal ulcer or keratitis?

The most common cause of a corneal ulcer or keratitis is bacterial infections. Bacterial keratitis is typically associated with contact lens use, where bacteria can enter the corneal tissue, leading to inflammation and ulceration. Common pathogens responsible for this condition include Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pneumoniae.

When bacterial infections occur, they can quickly cause significant damage to the cornea, often resulting in pain, redness, and decreased vision. This is particularly concerning because untreated bacterial ulcers can lead to severe complications, including corneal perforation and loss of vision.

Although viral infections, such as those caused by herpes simplex virus, are also significant causes of keratitis and can lead to corneal ulcers, they are generally less prevalent than bacterial causes overall. Fungal infections and allergic reactions can affect the cornea but are not the leading causes compared to bacterial infections. Thus, bacterial infections represent the most common etiology for this condition, highlighting the importance of prompt diagnosis and treatment to preserve vision.