Why is iris prolapse seen in certain corneal lesions?

Iris prolapse occurs when the iris, a part of the eye that controls the size of the pupil and the amount of light that enters, pushes forward through a perforation in the corneal tissue. In cases of corneal lesions where the integrity of the cornea is compromised, such as with ulcers or trauma, the iris can protrude into the corneal defect. This phenomenon acts as a natural response to help seal the perforation, preventing further exposure to environmental factors and reducing the risk of infection or additional damage.

By covering the hole, the prolapsed iris helps to preserve the internal structures of the eye and maintains intraocular pressure, which is critical for the overall health of the eye. Other options suggesting functions like protecting from pathogens or increasing light entry do not directly relate to the mechanism of iris prolapse in the context of corneal lesions. While tear drainage could be related to other aspects of ocular health, it does not explain the physiological response of the iris in the event of corneal damage.