EyeWorld Asia-Pacific March 2020 Issue

CATARACT 32 EWAP MARCH 2020 Chee Soon Phaik, MD Senior Consultant, Singapore National Eye Centre 11 Third Hospital Avenue, Singapore 168751 chee.soon.phaik@singhealth.com.sg ASIA-PACIFIC PERSPECTIVES C apsulotomy is one of the most important steps in cataract surgery. It affects the effective lens position and affects the refractive outcome. A decentered capsulotomy can cause lens tilt and decentration. An oversized capsulotomy especially in myopic eyes may contribute to increased incidence of toric implant rotation. In addition, capsule fibrosis that cannot be severed by tearing may incur a rhexis run-out. While manual capsulorhexis is strong and adjustable in size and position, it lacks precision even in experienced hands. In addition, centration on the capsular bag is not possible, unlike with certain femtosecond lasers. Today, new devices enable the novice and less skillful surgeon to create a precise and reproducible capsulotomy. In addition to the femtosecond laser, the list of available capsulotomy devices now includes Zepto (Mynosys Cellular Devices Inc, Fremont, CA) and more recently CAPSULaser (Excel-Lens, Los Gatos, CA). Femtosecond capsulotomy is precise, adjustable in size and centration on pupil, limbus or scanned capsular bag, which is especially helpful for subluxated lenses. However, its integrity and strength are weaker than capsulorhexis. Other issues include cost, the large footprint, need for an additional room and patient flow problems. Zepto creates a thermal capsulotomy using a precision nano-pulse capsulotomy device placed intracamerally. Hence, this device is challenging to use when the anterior chamber is shallow. In addition, the capsulotomy is fixed in size (5.2 mm), reducing its application in small eyes. Even though the capsulotomy is quick (0.004 s) and significantly stronger than capsulorhexis, anterior capsule rips may occur. However, the device has a small console and the device is affordable. Zepto can be used in complex cataract surgeries. CAPSULaser is a selective non-contact non-pulsatile laser capsulotomy device on fast acting trypan blue stained capsule, converting type IV capsule collagen to amorphous collagen which has increased elasticity and a rolled over edge anteriorly. This accounts for its increased tear strength over capsulorhexis. The laser is compact and mounted under the operating microscope. The capsulotomy size is variable and the procedure does not disrupt patient flow. Similar to Zepto, placement of capsulotomy is surgeon dependent, and centration on visual axis is recommended. While capsulorhexis for standard cataracts is good, I prefer the newer devices that provide the precision needed for premium lens implants. I also find them especially helpful in the management of complex cases such as intumescent cataracts and subluxated lenses, improving the ease and safety of surgery. Editors’ note: Dr. Chee has interests with Abbott Medical Optics, Alcon Laboratories, Bausch & Lomb Surgeries, Carl Zeiss Inc., and Ziemer Ophthalmics. The capsulorhexis overlaps the edge of the optic for 360 degrees but is large enough so that it does not cover a significant part of the optic. Source (all): Uday Devgan, MD IOLs, Dr. Devgan aims for a capsulorhexis that overlaps the edge of the optic 360 degrees while not covering a significant part of the optic. That means for the common IOL optic size of 6 mm, his ideal capsulorhexis is about 5–5.5 mm in diameter. “When we center this on the patient’s visual axis, we will be able to hold the IOL optic securely, thereby giving better predictability in the effective lens position used for IOL calculations, and better long-term stability and visual performance,” Dr. Devgan said. His approach applies to monofocal, multifocal, trifocal, extended depth of focus, and toric IOLs. Dr. Patterson strives for a capsulorhexis of 5.5 mm for the common 6-mm lens. “As the capsule opening gets smaller you are less likely to catch the edge of the optic on the edge of the anterior capsular rim and that’s a good thing, but if you get too far below 5 mm—and with the laser you could make these exactly the size you wanted—we learned that it started getting progressively more difficult to operate due to such a small opening.” For extremely dense cataracts, Dr. Patterson creates a 6.5–7-mm capsulorhexis. “With really rock-hard lenses, you need more room to maneuver, and with these very large openings there is no overlap at all,” Dr. Patterson said. Lens positioning impact The capsulorhexis plays a role in determining the final resting place of the optic—known as the effective lens position—when accounting for IOL calculations, Dr. Devgan said. “If most of the optic is overlapped by the capsulorhexis, even if it is less than the full 360 degrees, the effective lens position will likely be stable,” Dr. Patterson said. “[If] you are looking at the white- to-white and the center of the