FEB 2014

EyeWorld is the official news magazine of the American Society of Cataract & Refractive Surgery.

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Page 88 of 114

Besides a short corneal valve, a wider corneal tunnel compared to the sleeve and tip being used can c ause persistent egress of fluid with iris prolapse. So one has to identify if either or both of these problems are responsible for the iris prolapse. D. Rex Hamilton, MD, MS, FACS Director, UCLA Laser Refractive Center A ssociate clinical professor of ophthalmology Jules Stein Eye Institute, David Geffen School of Medicine at UCLA In the case presented here, the surgeon encounters iris prolapse through a clear corneal wound con- structed with a relative short tunnel length. An iris presenting at the wound during a routine case can surprise even the most experienced cataract surgeon. As a beginning surgeon, it is important to recognize the typical causes, warning signs and to understand the techniques for avoiding and handling the prolapsed iris to minimize sequelae. Etiology Iris prolapse occurs most commonly in the setting of a diaphanous iris such as in patients with pseudoexfo- liation syndrome or patients who have a history of systemic treatment with alpha 1-a antagonist medica- tions such as tamsulosin. In general, lighter colored irides have less rigid- ity and are more prone to intraoper- ative miosis and billowing than heavier pigmented irides. Overinfla- tion of the anterior chamber with viscoelastic (particularly dispersive) together with overly aggressive hydrodissection can lead to iris prolapse prior to introducing the phaco handpiece. This occurs due to the development of a large pressure gradient, which pushes the iris out of the higher pressure anterior chamber to the lower pressure exter- nal atmosphere. High flow rates cou- pled with poorly matched wound width and phaco sleeve diameter in- creases the risk of iris prolapse later in the case. The more posterior the clear corneal incision is placed and the shorter the tunnel length, the higher the risk of iris prolapse. Warning signs Immediately upon positioning the microscope, take note of the pupil diameter and appearance of the iris. If the iris is of lighter color, appears somewhat atrophic and has a poor dilation, the surgeon should look for early signs of iris instability. Upon i njection of viscoelastic, take note of the pupillary diameter change. If significant viscodilation occurs, this is a warning sign of possible instabil- ity. This should lead to a gentler hydrodissection and vigilance for detection of subtle iris billowing during hydrodissection. Pupillary miosis and/or iris billowing during p hacoemulsification are later signs of iris instability. Handling iris prolapse If iris prolapse occurs, there is higher pressure inside the eye than out. The first step to repositing the iris is to decrease this pressure gradient. Gen- tle pressure on the posterior lip of the paracentesis will allow egress of aqueous and/or viscoelastic from the eye, reducing the pressure gradient. A heavy, cohesive viscoelastic, some- times together with a cyclodialysis spatula, can then be used to gently push the iris back into the eye. If preservative-free, bisulfite-free phenylephrine or epinephrine is available (see below), it is never too late to use these agents, either through intracameral injection (preferable) or injection into the irrigating solution bottle. Late placement of a Malyugin ring or iris hooks can also be useful, taking care to identify and avoid capturing the capsulorhexis when engaging the pupillary border with these devices. Prevention Chang et al. recently reported an increased incidence of moderate to severe intraoperative floppy iris syndrome (IFIS) in low risk patients (e.g., no history of alpha 1-a antago- nist use) where no epinephrine was used in the irrigation solution. 1 About two years ago, preservative- free, bisulfite-free epinephrine be- came difficult to obtain. I noticed very quickly a significantly higher incidence of iris instability in many routine cases when epinephrine was not used in the irrigation solution. I have adopted the use of intracam- eral preservative-free, bisulfite-free phenylephrine 1.5%, which signifi- cantly reduces the risk of intraopera- tive iris instability. An immediate and significant mydriasis is noted following injection of intracameral phenylephrine. This solution, typi- cally compounded together with preservative-free lidocaine, is readily Wound continued from page 85 February 2014 84-90 Residents_EW February 2014-DL2_Layout 1 1/30/14 11:13 AM Page 86

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