Background
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). Intraoperative floppy iris syndrome is characterized by poor pupillary dilation, progressive pupillary constriction, and intraoperative iris billowing.[1]
Pathophysiology
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.[2] 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.
Epidemiology
Frequency
United States
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.
International
The incidence rate worldwide is unknown.
Mortality/Morbidity
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.
Race
No racial predilection exists.
Sex
Iris prolapse is probably more common in young men than in young women.
Age
Age is not a significant factor for iris prolapse.
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Allan BD. Mechanism of iris prolapse: a qualitative analysis and implications for surgical technique. J Cataract Refract Surg. Mar 1995;21(2):182-6. [Medline].
Albert DM. Ophthalmic Surgery: Principles and Techniques. Vol 1. Blackwell Science: 1999:137-138.
Brinton GS, Topping TM, Hyndiuk RA, et al. Posttraumatic endophthalmitis. Arch Ophthalmol. Apr 1984;102(4):547-50. [Medline].
Chang DF, Campbell JR. Intraoperative floppy iris syndrome associated with tamsulosin. J Cataract Refract Surg. Apr 2005;31(4):664-73. [Medline].
Francis PJ, Morris RJ. Post-operative iris prolapse following phacoemulsification and extracapsular cataract surgery. Eye. 1997;11 (Pt 1):87-90. [Medline].
McGwin G Jr, Hall TA, Xie A, et al. Trends in eye injury in the United States, 1992-2001. Invest Ophthalmol Vis Sci. Feb 2006;47(2):521-7. [Medline].
McGwin G Jr, Xie A, Owsley C. Rate of eye injury in the United States. Arch Ophthalmol. Jul 2005;123(7):970-6. [Medline].
Naylor G. Iris prolapse; who? When? Why?. Eye. 1993;7 (Pt 3):465-7. [Medline].
Taguri AH, Sanders R. Iris prolapse in small incision cataract surgery. Ophthalmic Surg Lasers. Jan-Feb 2002;33(1):66-70. [Medline].
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