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Managing iris prolapse during cataract surgery requires identifying cause, tailoring solution

Issue: September 10, 2012

ByPablo Arregui, MD

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One of the more frustrating issues that can happen during cataract surgery is to have the iris prolapse out of the incision. This can turn a simple surgery into a complicated one or at the very least alter the appearance of the eye postoperatively.

Ultimately, the reason the iris prolapses out of the wound is that the pressure behind the iris is greater than the pressure in front of the iris. The iris is simply following the pressure gradient. To solve this problem, one needs to identify the cause and then equalize or reverse this pressure gradient.

Causes of iris prolapse

Fortunately, when the iris prolapses, the surgeon usually has time to evaluate the situation and determine the underlying cause. Some of the most common causes are overly aggressive hydrodissection (balanced salt solution trapped behind the lens), ophthalmic viscosurgical device (OVD) behind the IOL (during IOL insertion), balanced salt solution misdirection, and intraoperative floppy iris syndrome (IFIS). Other causes include poorly dilated pupils (more exposed iris to flip up and out of the wound), hydrated vitreous (from a ruptured capsule or balanced salt solution getting pushed through the zonules; usually seen with a dispersive OVD), leaking or poor wound construction, patient Valsalva maneuver (from pain or a lid speculum that is too tight), traumatized or abnormal iris, suprachoroidal hemorrhage (entailing more to worry about than the iris), excessive retrobulbar anesthetic, and shallow anterior chambers.

Solutions to iris prolapse

Pablo Arregui

Instinctively, one usually wants to push the iris back into the anterior chamber through the primary incision. This urge must be resisted. Not only will this maneuver likely traumatize the iris, but the iris prolapse will almost always recur because the underlying problem of the pressure gradient has not been corrected. By identifying the specific cause, one can tailor the solution. The one common factor is that the treatment will very seldom involve going through the primary incision. Let us look at some of the more common causes and their specific solutions. With overly aggressive hydrodissection, excess balanced salt solution can become trapped behind the lens. This will cause the lens to come forward and push the iris forward along with it. To resolve this, the surgeon needs to get the excess balanced salt solution that is behind the lens to come forward. This is most easily achieved by entering through the paracentesis incision and pressing posteriorly on the lens and rocking it back and forth. This allows the balanced salt solution to escape into the anterior chamber and equalizes the pressure gradient. It helps to put a little posterior pressure on the paracentesis incision so that as the excess balanced salt solution comes forward, it can exit the eye.

Misdirected balanced salt solution is one of the most common causes of iris prolapse but also one of the easiest to treat. It usually happens when the phaco handpiece is too vertical and too close to the pupillary margin. When balanced salt solution gets directed behind the iris and pushes it forward, the act of the iris prolapsing forward usually self-corrects the pressure gradient. To ensure that it stays this way, pressing posteriorly on the paracentesis incision helps decrease the overall pressure within the anterior chamber.

There are many excellent articles that address IFIS. Not every patient on an alpha-adrenergic blocker will develop intraoperative iris problems. When they do arise, the most effective options are using Shugarcaine — 4% unpreserved lidocaine diluted with BSS Plus (Alcon) — in mild cases or iris hooks or rings in more severe cases. Sometimes, preoperative treatment with a long-acting dilating agent is also useful. In these cases, one wants to be careful that the incision is meticulously constructed, is located slightly more anteriorly, and is a little longer than usual.

Hydrated vitreous is sometimes seen with the use of dispersive OVDs. Balanced salt solution can be trapped and directed backward through the zonules by a dispersive OVD, which then pushes the lens and the iris diaphragm forward. Sometimes this can be difficult to identify or distinguish from other causes. To resolve this, one needs to enter through the paracentesis and burp out some of the OVD. This creates additional potential space in the anterior chamber and allows the balanced salt solution that is trapped behind the iris to come forward. Incidentally, if the iris and lens are coming forward and rocking the lens does not solve the iris prolapse problem, it is probably due to dispersive OVD pushing the lens and iris forward rather than balanced salt solution trapped behind the lens. Many surgeons who prefer dispersive OVDs like to burp a small amount out of the eye prior to doing their hydrodissection to create more space in the anterior chamber. This is why a soft-shell technique is usually preferred with a cohesive OVD, such as Healon (sodium hyaluronate, Abbott Medical Optics). The cohesive OVD in the soft-shell technique is much less likely to force the balanced salt solution posteriorly.

If there is significant wound leak or faulty construction, one can sometimes place a suture near the edge of the incision to effectively shorten it and minimize the problem. If this does not work, do not hesitate to abandon the incision and move 90° away to create a better incision. Of course, this may alter plans for astigmatic correction. If the patient is making Valsalva maneuvers, it is usually due to pain (have the anesthetist help with this) or could be because the lid speculum is too tight.

In previously traumatized eyes with prior iris damage or abnormal irises due to some other medical condition, consider using iris hooks or an iris ring early in the procedure. In some cases, using micro-scissors to cut any strands that might get caught in the phaco tip or irrigation and aspiration handpiece minimizes the damage. (It was not long ago that cutting the prolapsed iris and repositing the remains was considered an acceptable solution.) With shallow anterior chambers, consider preoperative Diamox (acetazolamide, Duramed Pharmaceuticals) and mannitol or a pars plana vitrectomy. Sometimes in extreme cases, a peripheral iridectomy can be performed to equalize the pressure gradient.

Finishing the procedure

Even after the cause has been identified and the problem has been corrected, sometimes the iris remains stuck in the incision. If this happens, use a cyclodialysis spatula or some other blunt instrument through the paracentesis incision to gently reposition the iris. If it does not easily return to its anatomic position, the problem has not been identified or fully corrected. Once the iris is back in position, it is critical to avoid having this problem recur. For most of these causes, once the problem has been identified and treated, the iris will no longer continue prolapsing out of the wound. If it does, consider lowering the bottle height and decreasing the flow and vacuum of the phacoemulsification machine. Additionally, one can add a small amount of dispersive or visco-adaptive OVD through the paracentesis over the iris prior to inserting any instrument through the primary incision. This can be done as often as necessary. Only a small amount of OVD is needed, and one should make certain that the OVD goes over the peripheral iris and not under it.

Summary

Although iris prolapse does not usually cause significant postoperative visual problems, one must be aware that this surgical inconvenience can quickly turn into a surgical disaster. Significant iris damage can lead to a patient with severe and chronic visual complaints who will revisit the office often, be unhappy and let other patients know it. If iris prolapse occurs, it is critical to identify the cause of the problem and treat the specific issue so that the pressure gradient in front and behind the iris is equalized. Of course, whenever possible, prevention is the key. Once an iris prolapses, it will have a tendency to prolapse over and over again. Anticipate and prepare for issues based on the patient’s medication list. Make sure the wounds are well constructed. Be careful not to overinflate the anterior chamber when hydrodissecting, especially with dispersive OVDs. Make sure the patient is comfortable before the procedure and remains so throughout the procedure. And of course, use careful surgical technique to minimize the likelihood of damaging the iris.