What is the condition characterized by the prolapse of the third eyelid?

The condition characterized by the prolapse of the third eyelid is known as cherry eye. This condition occurs when the gland of the third eyelid, which plays a crucial role in producing tears, becomes displaced or swollen, resulting in a visible protrusion. This prolapse can lead to irritation and inflammation of the eye, as the gland may not function properly if it is out of position.

In contrast, corneal ulceration involves damage to the cornea but does not specifically relate to the prolapse of the third eyelid. Ectropion is a condition where the eyelid rolls outward, leading to exposure of the inner eyelid surface, while entropion occurs when the eyelid rolls inward, causing the eyelashes to irritate the cornea. Neither ectropion nor entropion involves the third eyelid's gland or its displacement. Therefore, cherry eye clearly stands out as the condition involving the prolapse of the third eyelid.