Anterior Segment Cataract and Refractive
Achieving Best Visual Outcomes with a Monofocal Intraocular Lens James A Davison, MD, FACS Wolfe Eye Clinic, Marshalltown, Iowa
Abstract
Specific monofocal intraocular lens (IOL) design features have been integrated over time to provide improved vision performance after lens replacement surgery. Features of the AcrySof® IQ single-piece monofocal IOL (SN60WF, Alcon Laboratories) include architectural, chemical, and surface characteristics that improve performance over earlier designs. The architectural features include single-piece construction with low resistance to compression, 3D haptics for easy implantation, and predictable and stable long-term positioning. The foldable hydrophobic acrylic plastic provides efficient light focus and incorporates ultraviolet (UV) radiation and light-normalized spectrum transmission characteristics. The plastic’s surface incites minimal post-operative uveitis and capsule reaction and also resists epithelial cell proliferation. The biconvex optic is asymmetric with most of the power incorporated into the anterior surface to reduce dysphotopsia. The posterior surface has a base convexity and incorporates an aspheric modification. The optic’s square edge provides a barrier that discourages epithelial cell invasion and consequent posterior capsule opacification and need for neodymium-doped yttrium–aluminum–garnet (Nd:YAG) posterior capsulotomy, and is frosted to reduce dysphotopsia.
Keywords Intraocular lens, AcrySof®, light normalization, dysphotopsia, capsule opacification, haptic, optic, neodymium-doped yttrium–aluminum–garnet (Nd:YAG) posterior capsulotomy
Disclosure: James A Davison, MD, FACS is a paid consultant to Alcon Surgical. The author has no other conflicts of interest to declare. Acknowledgment: Technical editorial support was provided by Touch Briefings. Received: December 10, 2010 Accepted: February 28, 2011 Citation: US Ophthalmic Review, 2011;4(1):30–7 Correspondence: James A Davison, MD, FACS, Wolfe Eye Clinic, 309 East Church Street, Marshalltown, Iowa 50158. E:
jdavison@wolfeclinic.com
Support: The publication of this article was funded by Alcon Laboratories. The views and opinions expressed are those of the author and not necessarily those of Alcon Laboratories.
Following my appointment at the Wolfe Eye Clinic in 1980 I quickly learned phacoemulsification from my partners John Graether and Russ Watt in Marshalltown and from Dick Kratz, Tom Mazacco, Mike Colvard, and Bob Sinskey in Los Angeles. Even in those relatively early days, phacoemulsification with the Cavitron Kelman 8000 was an excellent operation; the first real small-incision surgery.1
However, after cataract removal, the incision needed to be enlarged for implantation of a polymethyl methacrylate (PMMA) acrylic intraocular lens (IOL). Ovoid PMMA IOLs (see Figure 1) were introduced to reduce the magnitude of incision enlargement but patients experienced more unwanted streaks and flashes after surgery2 condition now classified as positive pseudophakic dysphotopsia).3
(a
Similar to many surgeons, I used foldable silicone IOLs for a number of years, including several three-piece models from Allergan (SI18, SI20 and SI40) and a plate haptic model from STAAR Surgical (AA4203). They were great lenses and performed very well almost all of the time, but they had issues of their own. These lenses were associated with a relatively higher frequency of post-operative inflammation, posterior capsule opacification (PCO), capsule contraction, and optic
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displacement compared with PMMA lenses, plus intact capsulorhexis was needed in order to use the plate haptic IOL.4
Thus, there was an atmosphere of anticipation and excitement when the three-piece AcrySof® acrylic IOL (Alcon Laboratories) was introduced in 1995. For the first time, results similar to those obtained with acrylic PMMA lenses were achievable from a chemically similar but foldable acrylic IOL. Almost immediately it was observed that this combination of IOL chemistry and architecture was going to deliver significantly different results. The degree of post-operative inflammation was reduced, there was less reaction by the anterior and posterior capsules, and the incidence of cystoid macular edema (CME) also appeared to be reduced. Importantly, neodymium-doped yttrium– aluminum–garnet (Nd:YAG) laser capsulotomy rates appeared to plummet with the AcrySof® acrylic IOL as more of the posterior capsules stayed clear longer compared with PMMA, which itself had been better than silicone (see Figure 2).5–15
Many subsequent studies on capsular interaction and PCO have been published since the introduction of this square-edge foldable acrylic design. These studies have agreed that surgical perfection
© TOUCH BRIEFINGS 2011
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