The iris is a thin, colored diaphragm that is situated anterior to the lens. Although the root of the iris is attached to the ciliary body, the rest of the iris is unsupported. In the event of a corneal wound, the iris tends to prolapse out. Iris prolapse occurs when the iris tissue is observed outside of the wound; iris incarceration occurs when the iris tissue reaches the wound without prolapsing outside the eye.
Iris prolapse may also occur as part of a condition called intraoperative floppy iris syndrome (IFIS) during cataract surgery or trabeculectomy. This condition is associated with the use of several systemic alpha 1-adrenergic antagonists, such as tamsulosin (Flomax), as was first described by Chang et al in 2005 in patients undergoing cataract surgery. Intraoperative floppy iris syndrome is characterized by poor preoperative pupil dilation and intraoperative iris billowing, iris prolapse, and progressive pupillary miosis. 
Iris prolapse can occur when the cornea is perforated due to any cause.
In 1995, using flow mechanics and the Bernoulli principle, Allan provided a theoretical explanation of iris prolapse.  With a corneal perforation, the aqueous humor rapidly escapes, and a relative vacuum is created in front of the iris, thus leading to iris prolapse.
The exact incidence of iris prolapse in the United States is unknown, but the overall estimated rate of all eye injuries ranges from 8.2-13 per 1000 population. Eye injury rates are highest among individuals in their 20s, males, and whites.
The incidence rate worldwide is unknown.
Iris prolapse is a serious condition and, if left untreated, can result in infection and loss of the eye. If the prolapsed iris is exposed (eg, corneal laceration), immediate surgical intervention is needed because infection can spread through the iris and into the eye. If the prolapsed iris is covered by the overlying conjunctiva (eg, surgical wound), immediate surgical intervention is usually not needed.
No racial predilection exists.
Iris prolapse is probably more common in young men than in young women.
Age is not a significant factor for iris prolapse.
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