January 2009 Insert

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I recently had the opportunity to try the singlepiece aspheric IOLs developed by Advanced Medical Optics, Inc. (Santa Ana, California). With UV-only protection and an aspheric optic that provides -0.28 μm of spherical aberration, the company’s new Tecnis One is basically the Tecnis Z-9003 lens on a single-piece platform. I was initially struck at how similar the Tecnis One appeared to the AcrySof IQ IOL (Alcon Laboratories, Inc., Fort Worth, Texas), but after using both of these IOLs, I discovered some significant clinical differences.

MICRO-COAXIAL
I prefer to use a 2.2-mm, temporally located, singleplane corneal incision. I strongly believe that smaller, unenlarged, square incisions allow surgeons to decrease the risk of postoperative endophthalmitis and reduce surgically induced astigmatism. I can implant the AcrySof IQ IOL easily through a 2.2-mm micro-incision. I immediately discovered that the Tecnis One was much more difficult to implant through a 2.2-mm micro-incision. Ultimately, I had to move to a much larger (approximately 2.75-mm) incision to implant this lens comfortably. In comparing the same power of the Tecnis One and the AcrySof IQ, I found the former considerably thicker (Figure 1) and therefore more difficult to pass through the cartridge and surgical incision. This is primarily due to the low refractive index of the Tecnis’ material. Traditionally, the lower the refractive index, the thicker the lens. The AcrySof IQ’s thinner profile makes it much easier and safer to implant.

IMAGE QUALITY
The fact that the AcrySof IQ has a full-sized optic that can pass through micro-incisions offers patients significant advantages in terms of image quality. The Tecnis One does not provide patients with the benefit of a fully usable 6-mm optic (Figure 2). Several of my Tecnis One patients have clearly described dysphotopsias and optical aberrations that could be due to edge glare (Figure 3). Tecnis One’s potential for edge glare, caused by the scattered light from the junction between the usable and unusable optic, could increase when a pupil’s size is larger than 5 mm or if the lens is decentered. In addition to reducing the image quality of broadly dilated pupils, the Tecnis One’s reduced amount of usable optic may raise questions related to the effectiveness of its aspheric optic.

CLINICAL CONSIDERATIONS
Another readily apparent difference between the two single-piece platforms is their haptic designs. The Tecnis One’s haptic-optic orientation makes positioning it in the capsular bag somewhat awkward. My clinical impression is that the AcrySof IQ lens centers more easily and predictably. Additionally, the Tecnis One’s haptic-optic orientation places its optic plane well posterior to the haptic plane. As the capsular bag compresses following implantation, the potential for the optic to move posteriorly increases. This movement could result in a hyperopic shift and refractive surprises. In contrast, the AcrySof’s single-piece design adapts well to the contracting forces of the capsular bag and remains well centered and stable in the eye.

CONCLUSIONS
With more than 7 million AcrySof IQ IOLs implanted worldwide,1 it is understandable why companies would want to copy its design and performance. In my opinion, however, the Tecnis One falls short. I feel that the IQ’s proven single-piece aspheric platform remains unsurpassed in its stability, ease of implantation, and consistent outcomes. Like it is for many surgeons, the AcrySof IQ will remain my monofocal IOL of choice. ■

Quentin Allen, MD, is in group practice at the Illinois Eye Center in Peoria. He has received speaking and consulting fees from Alcon Laboratories, Inc., Allergan, Inc., and Ista Pharmaceuticals, Inc. Dr. Allen may be reached at +1 309 243 2400; q_allen@yahoo.com.
1. The 2008 Global IOL Market. MarketScope, LLC: St. Louis, MO; June 2008.

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