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    Clinical experience with a mechanical pupil dilator

    Cataract surgery in patients with small pupils is associated with a raft of complications including damage to and prolapse of the iris into a wound, the creation of a small anterior capsulorrhexis (leading to anterior capsule damage), incomplete removal of the cortical material, postoperative inflammation and a higher risk of posterior capsule rupture.1,2 

    Related: Overcoming challenges of pre-existing ruptured posterior capsule

    A small pupil also hampers visualisation of the peripheral capsule, making it difficult to ensure that the lens and haptics are placed completely in the bag.

    Achieving and maintaining adequate mydriasis is crucial in preventing serious complications. However, we are fortunate to have more interventions and instruments available than ever before to help us deal with these difficult cases.

    Managing small pupil size

    There are a number of options for increasing pupil size, including the use of intracameral mydriatics such as Shugarcaine and epi-Shugarcaine, viscodilatation and pupil-expansion devices. The pupil-expansion devices available include plastic and metal iris hooks, Clarke and Siepser rings, the Graether expander (Eagle Vision Inc.), the 5S iris ring (Morcher GmbH) and Perfect Pupil (Milvella Pty Ld), to name just a few.

    In the past, I nearly always used iris hooks in patients with small pupils. However, for my difficult cases, including patients with intraoperative floppy iris syndrome and pseudoexfoliation syndrome, I now almost always use the Malyugin ring (MicroSurgical Technology, Inc.).

    Related: How to reduce posterior capsular rupture

    The brainchild of Boris Malyugin, professor of ophthalmology and deputy director general at the S. Fyodorov Eye Microsurgery State Institution in Russia, the Malyugin ring was designed to overcome some of the disadvantages associated with other pupil expanders, such as overstretching of the iris sphincter and extended surgery time. The Malyugin ring is a square-shaped device made from 5/0 polypropylene with a paperclip-scroll design that holds the iris at eight equidistant points.

    The result is a round pupil, rather than the square one formed with four iris hooks, and circumferential protection of the iris (Figure 1). Helpfully, the device is available in two sizes, 6.25 mm and 7.00 mm, which offers a degree of flexibility. For example, while the 6.25 mm ring is suitable for most cases, the 7.00 mm ring is more suitable when placing an IOL with a large-diameter optic, or for surgeons who use the divide-and-conquer technique.

    Key advantages

    Cedric Schweitzer, MD
    Cedric Schweitzer, MD, is an ophthalmologist based at the University Hospital Bordeaux in France.

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