Efficacy of 360-Degree Square Edge on PC IOLs: Laboratory Study

David J. Apple, MD A. Vyas, MD, G. Kleinmann, MD, B. Zaugg, BS, Andreas F. Borkenstein, MD

David J. Apple MD Laboratory for Ophthalmic Devices Research2902 Brownell Avenue, Sullivan’s Island, SC 29482, USA

www.davidjapple.com

Dr. Apple receives research funding from Abbott Medical Optics,

Alcon Laboratories ,and Bausch & Lomb

American Society of Cataract & Refractive Surgery9-14 April, 2010, Boston, Massachusetts

Introduction & Background Posterior capsule opacification (PCO) and LEC induced fibrosis are major complications of cataract surgery. (Ref 1) During the last 25 years, there has been a significant decrease of the PCO rate. (Ref 2 & 3) However, we have found that in reality the PCO is generally delayed rather than prevented. (Ref 4) The optic geometry is one of the six major factors that we have found that are required to reduce the rate of PCO.

Michael Amon of Vienna has made clinical observations and David Apple has made pathological observations suggest that a 360° ridge added to a 1-piece PC-IOL’s square edged-optic may help lower the overall incidence of PCO. The absence of a square edge subtending the region of the haptic-optic junction may in effect act as an “Achilles Heel“ permitting growth of cells over the haptic/optic junction.

A study by Vyas and Associates has confirmed this. (see below)

PurposeIn this study we provide evidence, based on a compilation of information from several sources, utilizing various techniques, that indeed support the contention that the 360° enhanced square optic edge design is an important factor for PCO delay and prevention.

Until fairly recently all PMMA optics had a square edge that covered the perimetry of the optic

except the region underlying or subtending the haptic-optic junction. We illustrate this phenomenon here in two examples: the Alcon Acrysof Platform (left) and the Rayner hydrophilic lens (Centreflex). These 2 IOLs have a gradual transition of the haptics and optics at their junction (arrows, no extra PCO protection).

The Problem

Method 1: Manufacture of the 360° Edge by Rayner, Ltd. These are 3 SEM examples of views of the lens‘ optic/haptic junction where a barrier or ridge (arrows) exists for 360°.

The Solutions

Methods 2: Experimental Animals

Reference 5

A study performed in the Apple LaboratoryImplantation of a Rayner Centreflex in rabbits. Histopathologic analysis after sacrifice.

A B

C

A. No enhanced 360° edge, in-growth of cells (arrows) from the haptic/optic junction (right)

B & C. In-growth of cells is completely blocked by a 360° enhanced edge. The lens’ optic remains totally clear.

From Vyas and Associates (Ref 6)

Methods 3: Kinetic StudyClincial photographs from a brilliant study by Vyas and assoc., shows eyes taken at 2-year follow-up. Figures A and B, show the drawings that were used to grade the barrier effect at the haptic-optic junction. The centripetal migration of LECs was observed and drawings of individual LECs were made.

Figure A: An enhanced edge was present with no penetration of the barrier.

Figure B: No enhanced edge: No inhibition of cells.

A

B

Methods 4: Clinical Observations

FDA Statistics, 2006 – NdYAG Rates (2 Years)

Before 2003 15%(No enhanced edge)

After 2003 5%(With an enhanced edge)

A lens with no enhanced edge. This single case report from Japan shows how LECs may grow in behind the optic at the unprotected haptic-optic junction.

From Sugita and Assoc. (Ref 7)

A. Alcon Laboratories has not applied an enhanced edge to their Acrysof platform believing that this added protection is not necessary. The haptic-optic junctions are therefore not protected with an enhanced edge. However, the NdYag laser rate of this platform has been shown to be higher than previously assumed, and our studies suggest that an application of this design would be efficacious. (Reference 4)

B. The hydrophobic acrylic lens design marketed by Hoya has haptic-optic junction protection, with a built in enhanced edge (arrow).

A

B

Current Applications Abbott Medical Optics (AMO) Tecnis® 1-Piece Lens Design

• PROTECTM 360° Edge Design– The 360° square edge is present, forming a complete 360° enhanced edge.

Abbott Medical Optics has applied a 360° complete, enhanced square edge, designed to render complete protection at the haptic-optic junction.

Conclusions The basic square optic edge is an important design feature for PCO prevention.

However, it should be present for 360° around the optic to provide an effective complete barrier effect capable of blocking cells.

A lens with an incomplete square edge is rendered an “Achilles Heel“, allowing growth of cells over the unprotected haptic-optic junction.

With the enhanced edge there is a lesser chance for penetration of cells across this barrier.

1. Apple DJ, Soloman KD, Tetz MR, et al. Posterior capsule opacification. Surv Ophthalmol 1992; 37: 73-116.

2. Apple DJ, Peng Q, Visessook N, et al. Eradication of posterior capsule opacification; documentation of a marked decrease in Nd:YAG laser posterior capsulotomy rates noted in an analysis of 5416 pseudophakic human eyes obtained postmortem. Ophthalmology. 2001;108:505–518.

3. Peng Q, Visessook N, Apple DJ, et al. Surgical prevention of posterior capsule opacification: Part 3: Intraocular lens optic barrier effect as a second line of defense. JCataract Refract Surg 2000; 26: 198-213.

4. Apple DJ, Presented at the Annual meeting of the ASCRS, Innovators Session, Chicago, 2008. (Published in Ophthalmology Times, May 15, 2008)

5. Werner L, Mamalis N, Pandey S, et al. Posterior capsule opacification in rabbit eyes implanted with hydrophilic acrylic intraocular lenses with enhanced square edge. J Cataract Refract Surg 2004; 30: 2403-2409.

6. Vyas A, Narendran R, Bacon P, Apple DJ. Three hundred-sixty degree barrier effect of a square-edged and an enhanced-edge intraocular lens on centripetal lens epithelial cell migration: Two-year results. J Cataract Refract Surg 2007; 33: 81-87.

7. Sugita M, Kato S, Sugita G, et al. Migration of Lens Epithelial Cells Through Haptic Root of Single-piece Acrylic-foldable Intraocular Lens. Am J Ophthalmol 2004;137:377-379.

References