Viscoadaptive OVDs and modified prolate IOLS for better outcomes in cataract surgery
©2004. Robert M. Kershner, M.D., M.S., F.A.C.S.
Boston, Massachusetts USA
Surgeons today have a wide range of surgical devices and IOLs to choose from. In this article, I describe two of the newest additions to our armamentarium in the quest for the perfect cataract procedure. Healon (Advanced Medical Optics [AMO], Santa Ana, Calif.) was the first ophthalmic viscosurgical device (OVD) available to surgeons with Healon5 (AMO) the latest evolution in a new generation of OVDs known as the viscoadaptives. The Tecnis Z9000 IOL (AMO) is the first modified prolate anterior surface IOL to be approved in the United States by the Food and Drug Administration. Together, these products represent firsts in their technology and deserve close attention as ophthalmologists enter the next generation of cataract procedures.
The advent of ophthalmic viscosurgical devices (OVDs), also known as viscoelastics, has made surgery safer and allowed surgeons to tackle cases they previously would never have considered.
OVDs are generally available in three categories —dispersive, cohesive and viscoadaptive. OVDs should be considered surgical instruments, and, just as with all surgical instruments, surgeons must know how they are used and to remove them at the end of a procedure.
The family of Healon products covers the entire spectrum of OVDs — Healon, Healon GV and Healon5.
Each Healon product has different characteristics. Healon, as a cohesive, with a low water content, allows surgeons to work within it during surgery. Healon GV is slightly more viscous and more of a formed substance, allowing it to be better used to control tissue. Comparatively, Healon5 is like liquid glass, requiring purposeful insertion and removal. The advantage to Healon5 is that it will stay in place, it is clear, and it does not obscure surgical visualization.
One of the concerns in using a highly viscous OVD is that it causes a postoperative rise in IOP. A study by Steven Arshinoff, MD, demonstrated that as long as Healon5 is removed at the conclusion of surgery, a rise in IOP can be avoided.(1)
Some surgeons believe that Healon5 should be used in only difficult cases. I have found that it can be helpful in every surgical case, as long as surgeons understand how to use it properly. A little goes a long way, so I would advise surgeons to use Healon5 sparingly and only where it is needed.
Silicon – A surgeon’s new friend
Yes, silicon, not silicone, is the ophthalmic surgeon’s new friend. Construction of a proper cataract surgical incision can facilitate a successful outcome. Surgeons prefer diamond, the sharpest surgical blade material possible. Since diamond is expensive, fragile and requires special handling, use of the next hardest element, silicon, may be an excellent alternative.
Silicon is best known as a semiconductor material used in microchips. That technology has recently been applied to the BD Atomic Edge Surgical Blade (Becton Dickinson, Franklin Lakes, N.J.). The blade can be used to construct a diamond-like incision, but in a disposable and inexpensive surgical product.
With today’s IOLs, it is critical that the capsulorrhexis be centrally located and perfectly round. Healon can deepen the anterior chamber for capsulorrhexis to reduce stress on the capsule and zonules. Healon5 can then be inserted onto the center of the lens creating a convexity to the capsule. The tear can then be made around the Healon5.
Healon5 can be injected under the incisional lip after the capsulorrhexis is completed to allow for access into the eye without capturing the endothelium or iris, prior to the start of phaco.
After phaco is complete, Healon5 can be used to lubricate the injector cartridge, which facilitates insertion of the IOL with a minimum amount of friction. Healon5 can be used to control the IOL as it enters the bag. By inserting a small bolus of Healon5 in the center of the capsule opening, surgeons can then place the injection cartridge underneath the ball, inject the IOL, displacing the Healon5 anteriorly and keeping the IOL in the bag.
Advances in IOLs
In more than 50 years since the first implantion of an IOL by Sir Harold Ridley, there have been amazing advances in cataract surgery, including the latest wavefront application to IOL design. I believe wavefront technology may make spherical IOLs obsolete.
In a study I published in the Journal of Cataract and Refractive Surgery , three IOLs — the Tecnis Z9000 IOL (AMO) with polysiloxane optic and polyvinylidine fluoride haptics, the AA4207-VF silicone one-piece lens (Staar Surgical) and the AcrySoft acrylic lens (Alcon, Fort Worth, Texas) — were studied for their ability to improve functional vision.(2)
Surgery was performed with topical anesthesia, a small clear corneal incision, phaco and injection of the IOL into the capsular bag. Data showed that in the first month, patients who received the Tecnis IOL had better uncorrected visual acuity than the other groups.
There was a 47% improvement in functional visual acuity with contrast testing during the day with the Tecnis IOL. At night, there was greater than 100% improvement in contrast, which was superior to the other IOLs in the study.
Fundus photography was performed before surgery and again 3 months after surgery.
All three lenses provided patients with improved visual acuity. In the groups implanted with the AcrySoft and AA4207 IOLs there was little or no improvement in functional vision with contrast testing compared to preoperative cataract. With the Tecnis IOL, there was an improvement of 40% in contrast imaging of the fundus.
Performing surgery with Healon5 enhances surgical reproducibility and safety in my hands. The improved functional vision that the Tecnis IOL provides, results in increased patient satisfaction and better outcomes. I have found that Healon5 and Tecnis are ideal partners for today’s cataract procedure.
Arshinoff SA, Albiani DA, Taylor-Laporte J. Intraocular pressure after bilateral cataract surgery using Healon, Healon5, and Healon GV. J Cataract Refract Surg . 2002;28(4):617-625.
Kershner RM. Retinal image contrast and functional visual performance with aspheric, silicone, and acrylic intraocular lenses. Prospective evaluation. J Cataract Refract Surg . 2003;29(9):1684-1694.