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.[1]
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.
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.
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.
The iris is a sensitive tissue in the eye. At the time of an iris prolapse, patients often experience pain. Patients with a perforated corneal ulcer frequently provide a history of severe pain that has since subsided.
The iris can prolapse after surgery (eg, cataract, corneal transplant), following trauma (eg, corneal laceration, scleral laceration), through a perforated corneal ulcer, or through a corneal melt associated with rheumatoid arthritis.
With improvements in microsurgical techniques, iris prolapse after surgery is uncommon.
Iris prolapse with a perforated corneal ulcer is rare.
In the author's experience, the most common cause of iris prolapse is following trauma; however, the exact incidence is not known.
In peripheral iris prolapse, the iris appears as a knuckle of colored tissue, resulting in a partial peripheral synechia. When the prolapse is central, the entire pupillary margin may prolapse, resulting in a total anterior synechia. In patients with a perforated cornea, the prolapsed iris is exposed.
Depending on the duration of prolapse, the appearance of the iris may vary. In cases of recent prolapse, the iris appears viable. With time, the iris appears dry and nonviable. In patients who have undergone corneal transplant surgery or cataract surgery with a clear corneal incision, the appearance of the iris is the same as in a perforated cornea. When the iris prolapses through a scleral wound, it appears as a colored mass beneath the overlying conjunctiva. In this case, the iris remains viable for a long time.
The pupil appears peaked in the region of the iris prolapse. The anterior chamber is formed as the prolapsed iris seals the wound. Minimal or no wound leakage occurs. Wound leak is verified using the Seidel test. A drop of 2% fluorescein sodium is instilled in the conjunctival sac. The wound is examined under the slit lamp with cobalt blue light. The fluorescein appears greenish. Wound leak can be easily identified when the fluorescein is diluted by the aqueous humor. Gentle pressure on the eye may be needed to induce leakage.
Intraocular pressure is lower than normal, but hypotony is uncommon after iris prolapse.
In long-standing iris prolapse, chronic iridocyclitis, cystoid macular edema, or glaucoma may be seen. The prolapsed iris may act as a scaffold for infection, epithelial downgrowth, or fibrous ingrowth. Rarely, sympathetic ophthalmia may occur. Carefully examining the fellow eye for cells and flare is important.
Intraoperative floppy iris syndrome is graded as follows:[3]
Iris prolapse can occur following trauma, after surgery, through a perforated corneal ulcer, or through a corneal melt.
In long-standing iris prolapse, if cystoid macular edema is suspected, ocular coherence tomography (OCT) and fluorescein angiography may be performed. Cystoid macula edema appears as intraretinal edema on OCT and flower petal leakage in the macula in the late stages of the angiogram.
CT scan of the orbits is indicated with traumatic iris prolapse to aid in diagnosing other ocular and orbital trauma. CT scan of the orbits may help in localizing intraocular foreign bodies and in assessing the status of the posterior segment of the eye.
In traumatic iris prolapse, ocular ultrasound may be gently performed by experienced personnel. This imaging modality may help to locate intraocular foreign bodies and to assess the status of the posterior segment of the eye. Care should be taken while performing the ocular ultrasound because undue pressure can cause prolapse of the intraocular contents.
Iris prolapse is a serious condition that requires prompt medical management. As soon as the diagnosis is made, an eye shield should be applied to prevent further damage. Medical treatment is only indicated when the prolapse is small, is covered by the conjunctiva, and is without any other complications. In these cases, the eye may be observed.
Antibiotic eye drops and cycloplegics may be used during the acute stage. Intravenous antibiotics should be considered because infection from an iris prolapse can spread to the intraocular contents. Tetanus toxoid may be considered depending on the immunization status and the wound type.
In a prospective randomized study of 81 patients undergoing cataract surgery taking oral alpha-adrenergic agents, subtenon injection of 2% lidocaine significantly reduced the incidence of intraoperative floppy iris syndrome compared to 1% intracameral lidocaine.[4]
Prompt surgical management is necessary when conjunctival coverage is not present or in the presence of complications. The primary goal of surgery is to restore the anatomical integrity of the eye. Visual restoration is only a secondary goal.[5]
General anesthesia should be used during surgery. Retrobulbar anesthesia and peribulbar anesthesia are not recommended because they increase both intraorbital pressure and loss of additional intraocular tissue; however, they may be used if general anesthesia is contraindicated.
In cases of peripheral iris incarceration and a well-formed anterior chamber, acetylcholine (Miochol) may be administered. Acetylcholine is instilled through a paracentesis incision into the anterior chamber with gentle stroking of the iris. Acetylcholine constricts the pupil and may release the iris incarceration. Similarly, if the iris incarceration is central, intraocular epinephrine may be administered. Epinephrine dilates the pupil and helps to release the iris incarceration.
If unsuccessful through a paracentesis incision, a viscoelastic agent is injected into the anterior chamber in the region of the iris prolapse. This mechanical force may be enough to release the prolapse and to reposition the iris. If the prolapse occurred within the previous 24-36 hours and if the iris is viable, the iris is reposited. If the iris does not appear viable, then it is excised. The iris should be excised if signs of epithelialization are present. To excise, the prolapsed iris is cut flush with the corneal surface. The iris defect may be closed using a 10-0 polypropylene suture on a vascular needle.
If the viscoelastic method is unsuccessful, then a cyclodialysis spatula with the longer end is introduced through the paracentesis incision. The spatula is swept from the center to the periphery of the prolapse to avoid unnecessary tension on the iris root. The corneal wound may be sutured depending on its length and integrity.
If the iris prolapse occurs after surgery, the same principle is used. The wound must be revised, or additional sutures should be applied to make the wound watertight.
When the iris prolapse occurs after a corneal perforation, the iris can be reposited. Cyanoacrylate glue and a bandage contact lens may be used to seal the perforation. If unsuccessful or if the perforation is large, an emergency corneal transplant is necessary.
Intraoperative floppy iris syndrome may be managed via modification of cataract surgical technique, use of preoperative atropine drops for pupillary dilation, intracameral epinephrine, ophthalmic viscoelastic devices, iris retractors, and pupil expander rings.[3]
In patients with a corneal melt due to medical causes (eg, rheumatoid arthritis), appropriate consultations must be obtained.
The patient should not engage in contact sports because even a minor trauma can cause significant damage in an already compromised eye. The patient should be instructed to wear polycarbonate eyeglasses while working with mechanical devices and tools.
Systemic antibiotics are used for prophylaxis against infection, especially in cases of iris prolapse following trauma. Endophthalmitis is uncommon but has a poor prognosis in the setting of ocular trauma. Antibiotics should cover both gram-negative organisms and gram-positive organisms, including Bacillus, which is the most common cause of posttraumatic endophthalmitis.
Clinical Context: Provides excellent coverage of gram-positive organisms, including Bacillus. To avoid toxicity, current recommendation is to assay vancomycin trough levels after third dose drawn 0.5 h prior to next dose. Use creatinine clearance to adjust dose in patients with renal impairment.
Clinical Context: Third-generation cephalosporin with broad-spectrum, gram-negative activity; lower efficacy against gram-positive organisms; higher efficacy against resistant organisms. Arrests bacterial growth by binding to one or more penicillin-binding proteins.
Clinical Context: Quinolone that has antimicrobial activity based on ability to inhibit bacterial DNA gyrase and topoisomerases, which are required for replication, transcription, and translation of genetic material. Quinolones have broad activity against gram-positive and gram-negative aerobic organisms. Differences in chemical structure between quinolones have resulted in altered levels of activity against different bacteria. Altered chemistry in quinolones result in toxicity differences.
Clinical Context: Indicated to treat bacterial conjunctivitis. Elicits antimicrobial effects. Inhibits topoisomerase II (DNA gyrase) and IV enzymes. DNA gyrase is essential in bacterial DNA replication, transcription and repair. Topoisomerase IV plays a key role in chromosomal DNA portioning during bacterial cell division.
Corneal sutures may be removed when they become loose or in stages after 4-6 weeks.
Long-term follow-up care is necessary to monitor intraocular pressure and cataract formation. In patients who are medically treated, the eye should be carefully examined for iritis and cystoid macular edema. The fellow eye should be carefully examined for signs of sympathetic ophthalmia.
After surgery, patients may be monitored on either an inpatient basis or an outpatient basis. Admitting patients for at least 1 day after surgery is recommended.
Postoperatively, patients are prescribed antibiotics, steroid drops, and cycloplegics for 3-6 weeks.
The patient should be instructed to wear protective eyeglasses that cover the eye from the front and the sides while working with mechanical devices and tools or during contact sports. (The author recommends avoiding contact sports.) The protective eyeglasses should be made of polycarbonate, a shatterproof material.
Several complications can occur because of an iris prolapse, as follows:
Prognosis depends on several factors. The smaller the prolapse, the better the prognosis.
Patients with other injuries and intraocular foreign bodies are likely to have a poor prognosis.
The presence of infection carries a poor prognosis.
Epithelial downgrowth and fibrous ingrowth are difficult to treat and have a poor prognosis.
For excellent patient education resources, visit eMedicineHealth's Eye and Vision Center. Also, see eMedicineHealth's patient education article Eye Injuries.