November 2014

 

CATARACT

 

Newcomer in the ring


by Maxine Lipner EyeWorld Senior Contributing Writer

 
   

Standard forceps are used to create the anterior capsulorhexis, with care taken to guide the anterior leaflet against the inner wall of the ring. This will ensure a well-centered and perfectly sized rhexis.

Source: Malik Y. Kahook, MD

Unique device aids in capsulorhexis creation

It is the most difficult part of cataract surgery to learn: the creation of the capsulorhexis, according to Malik Y. Kahook, MD, Slater Family Endowed Chair in Ophthalmology and chief of the glaucoma service, University of Colorado, Aurora, Colo. However, a new caliper-like device that he has pioneered will help alleviate some of the anxiety around this, he thinks. The device, known as the Verus Capsulorhexis Device (Mile High Ophthalmics, Denver), is a ring that can assist with sizing and centration of the rhexis. Recent results published in the May issue of the Journal of Cataract & Refractive Surgery showed that the Verus consistently helped practitioners make a well-centered 5.5 mm rhexis. The creation of the rhexis is typically the step that causes the most anxiety and is most vexing for both the resident and the physician supervising the training, Dr. Kahook said. Its an extremely difficult skill to master and takes a lot of time and finesse to achieve consistency. Even seasoned physicians who have done thousands of capsulorhexis procedures are frequently off target on centration and sizing. Recent use of the femtosecond laser has introduced many to the importance of a consistent size and position of the rhexis in terms of improving outcomes. Still, the technology has some issues, including access and cost, Dr. Kahook said. In addition to costing $500,000 for the femtosecond unit, for each case there are docking fees of hundreds of dollars, making this cost prohibitive for many. Centration of the rhexis with the femtosecond laser must be done prior to visualization under the operating microscope, which is not ideal since anatomy is not as clear under the femtosecond system view. What is more, the femtosecond capsulorhexis relies on a can-opener technique in which multiple perforations are connected, whereas a continuous curvilinear capsulorhexis (CCC) is stronger, Dr. Kahook said, adding that the Verus helps create a CCC that is familiar to surgeons.

Creating a better rhexis

Dr. Kahook, who trains many residents and fellows, was first inspired to develop the device with the novice surgeon in mind. I was trying to think of ways to make it safer for the patient as well as a better experience for the learning resident and the physician doing the teaching, he said. We came up with multiple designs to figure out what would be the least disruptive to the flow of cataract surgery. The Verus was 1 of 5 designs considered. It is a ring made out of medical-grade silicone, with an internal hole that has a diameter of 5.5 mm. The device is designed with enough surface area between the inside and outside diameter so theres a significant amount of surface in contact with the anterior capsule, he explained. The bottom part of the ring is micro-patterned to provide for more stability once the ring is placed on the anterior capsule. As a result, despite the creation of a capsulorhexis along the internal diameter of the device, there is minimal movement relative to the capsule, which allows for precise capsulotomies.

Once you have the device in place with viscoelastic over it, you can then perform the capsulorhexis as you usually would, Dr. Kahook said. After creating the initial anterior capsular flap, the practitioner would walk the leading edge along the inner wall of the ring. Youre hugging the inside diameter of the ring and that allows you to make sure youre staying consistent as far as the diameter of the rhexis youre creating, he said. It also allows you to keep the rhexis centered where you want it because if youre hugging the internal diameter of the ring, the final product will be centered exactly where you have the ring centered. This is what recent study results indicated. We showed in the paper that we were consistent in the size of the rhexis that was created, Dr. Kahook said. The device was tested on 20 cadaver eyes and in every case the resulting capsulorhexis was the desired 5.5 mm. It was extremely consistent, both in size and centration, without any rents or peripheral tears with the capsulorhexis as we were creating it.

Easy adaptation

Investigators also found it easy to use. To prove that it was straightforward, he had a first-year resident try it and found the new practitioner was able to achieve a perfectly round, centered capsulorhexis. In addition, Dr. Kahook had a lab technician with no surgical experience give it a try, with the same results. A medical student, Matt Powers, worked with Dr. Kahook on the design and execution of the study and also actively tested the device with great success. They identified several steps as key to successful use of the device including: 1) insertion of the device into the anterior chamber prior to complete filling with viscoelastic followed by completing the viscoelastic installation over the device to enhance adhesion; 2) starting the capsulorhexis flap in the central part of the lens, then lifting it up and walking it toward the internal edge of the Verus device with forceps; and 3) ensuring that the capsular flap is walked along the inner edge of the Verus while being lifted slightly over the device so that the cut in the capsule is occurring in a manner similar to ripping a piece of paper against an overlying ruler.

Dr. Kahook thinks the Verus will help surgeons in developing countries where they are only now adopting phacoemulsification. This device will give them a way to get a perfectly centered and sized rhexis without having to go through the complication of learning to do the procedure on their own, he said. Even expert surgeons can benefit from the enhanced positioning and sizing of their rhexis using Verus routinely. The final version of the Verus device will be micro-patterned on both sides so that insertion does not require top/bottom orientation. Dr. Kahook expects the Verus to be available to surgeons by the end of 2014.

Reference

Powers MA, Kahook MY. New device for creating a continuous curvilinear capsulorhexis. J Cataract Refract Surg. 2014 May;40(5):82230.

Editors note: Dr. Kahook has financial interests with Mile High Ophthalmics.

Contact information

Kahook: malik.kahook@gmail.com