Taming “Misbehaving” Irises

Too-small, too-large, floppy, and damaged irises must be addressed. Howard Larkin reports from the American Glaucoma Society 2022 annual meeting.

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Too-small, too-large, floppy, and damaged irises must be addressed. Howard Larkin reports from the American Glaucoma Society 2022 annual meeting. Small, large, floppy, or damaged irides complicate cataract and glaucoma surgery. Gayle C Howard MD, PhD offered pearls for getting them under control at the American Glaucoma Society 2022 annual meeting. Small or poorly dilating pupils can result from medications, older age, or inflammatory or neovascular membranes—though 25% occur with no known risk factors. Intraoperative floppy iris syndrome often results from taking tamsulosin or other alpha blockers. Bleeding with dilation and sphincter tears are other causes of erratic iris behaviour. All increase the risk of complications such as capsular rupture, retained fragments and CME, and increase surgery time and surgeon anxiety, Dr Howard said. For cataract surgery, the iris sometimes can be stretched with a second instrument, such as a Kuglen iris hook or collar button. When this does not allow sufficient room for surgery or prevent iris tissue from occluding the phaco tip, she advises deploying other techniques. Iris hooks are one, though these require additional corneal incisions and are time consuming to insert and remove. Malyugin rings have the advantage of easier insertion and no extra incisions. Non-device options include Omidria® (Omeros), and while this prevents miosis and maintains iris tone, it is expensive. When membranes prevent dilation, peeling them in segments can help, though this may involve some bleeding. If peeling is not effective to allow a larger pupil, hooks or a Malyugin ring may also be needed. SUTURING In the case of traumatic mydriatic pupils, a McCannel suturing technique can reduce pupil size. This involves running a suture through a pair of corneal paracenteses, then through two points in the iris, drawing the suture points together by tying a knot through another corneal incision midway between the suture insertion and exit points and allowing the knot to retract back into the eye. The process can be repeated to achieve the desired pupil size, Dr Howard said. The Siepser suturing technique is similar but uses slip knots to pull the iris together, eliminating the need for a third incision. Videos and schematics of both techniques can be found online. GLAUCOMA SURGERY For microincision glaucoma surgery, Dr Howard cautioned avoiding engaging iris tissue in the angle or when entering or leaving the eye. Using cohesive viscoelastics and pupil constriction medications can help. She also said plugging the shunt or device with iris tissue or tearing the iris root can be avoided in trabeculectomy or tube surgery by determining the correct angle for insertion and positioning. A second instrument can push the iris out of the way—or viscoelastic can deepen the chamber and push the iris posteriorly. For cyclophotocoagulation, too much power can lead to permanent mydriasis, Dr Howard noted. Power should be reduced and not applied at the three and nine o’clock positions to avoid this problem. “Dealing with the iris is just like Goldilocks—not too small, not too big, and not too soft or floppy. Use devices, medicines, and suturing to get it just right,” Dr Howard said. Gayle C Howard MD, PhD practices in Chula Vista, California, USA. gchoward1@yahoo.com