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Anterior Segment Intraocular Lens
Edge Profiles of Currently Available Intraocular Lenses
and Recent Improvements
Liliana Werner
1,2
and Manfred Tetz
1
1. Berlin Eye Research Institute (BERI); 2. John A Moran Eye Center, University of Utah, Salt Lake City
Abstract
We evaluated the microstructure of the edges of currently available foldable intraocular lenses (IOLs). The methodology used assisted an
IOL manufacturer (Hoya, Japan) to optimise the edge profile of its lenses. Ten designs of hydrophobic acrylic, six designs of silicone and 24
designs of hydrophilic acrylic IOLs were imaged under scanning electron microscopy (SEM), and the photographs were imported to a digital
computer program. The area above the posterior–lateral edge, representing the deviation from a perfect square, was measured in square
microns. There was a large variation of the area values measured in currently available foldable IOLs labelled as square-edged lenses. As
a group, the edges of hydrophilic acrylic lenses were less square than those of hydrophobic acrylic and silicone lenses. Hydrophobic acrylic
AF-1 Hoya lenses had a high area value (329.7µ
2
). Through manufacturing changes, the edges of the lenses were then optimised to a value
down to 39.1µ
2
, which represents the most square hydrophobic acrylic edge currently available.
Keywords
Intraocular lens (IOL), hydrophobic acrylic, silicone, hydrophilic acrylic, poly(methyl methacrylate), posterior capsule opacification
Disclosure: Supported by a 2007 Research Grant from the European Society of Cataract and Refractive Surgeons (ESCRS), and by unrestricted research grants to the Berlin
Eye Research Institute from Hoya, Oculentis, Alcon, Advanced Medical Optics, Inc. (AMO) and Advanced Visual Systems (AVS).
Received: 31 July 2009 Accepted: 18 August 2009
Correspondence: Liliana Werner, Berlin Eye Research Institute, Alt-Moabit 98/99, D-10559, Berlin, Germany. E: werner.liliana@gmail.com
Posterior chamber intraocular lenses (IOLs) with a square posterior and observing bovine LEC growth over 18 days on average. Results
optic edge have been associated with better results in terms of demonstrated that the lower the area value, the better the cell
posterior capsule opacification (PCO) prevention, regardless of the blockage in culture.
material used in their manufacture.
1–3
Although this IOL design feature
can be appropriately assessed in morphological studies using Study on Commercially Available Hydrophobic
scanning electron microscopy (SEM), such studies of new IOLs have Acrylic and Silicone Intraocular Lenses
generally focused on the quality of the optic surface or optic Commercially available lenses manufactured from hydrophobic
finishing.
4,5
At the Berlin Eye Research Institute, a series of studies acrylic and silicone materials were obtained for use in this series of
were carried out to define and quantify the edge of square-edged studies through letters sent to IOL manufacturers.
7
All of them were
IOLs.
6–8
The methodology used in these studies can be used to marketed as having a square optic edge for PCO prevention.
optimise the square edge profile of IOLs. Generally, two IOLs of each design were evaluated: +20.0D and +0.0D
whenever available for a particular design. If +0.0D was not available,
Study on Experimental Polymethylmethacrylate the lowest dioptric power was used for that particular design. We
Intraocular Lenses used an improved methodology to evaluate the optic microedge
Tetz and Wildeck made the first attempt to evaluate and quantify at a structure of currently available lenses.
microscopic level how sharp the optic edge must be to effectively
prevent lens epithelial cells (LECs) from growing onto the posterior Each IOL was carefully removed from its original packaging with a
capsule.
6
Plano +0.0D polymethylmethacrylate (PMMA) IOLs with 11 toothless forceps and mounted on a support for SEM analysis. During
defined edge designs were specially manufactured for use in this SEM examination, the analysis of each optic edge was performed from
preliminary in vitro study. To obtain different edge designs, the IOLs a perpendicular view. Photographs of the optic edge of each IOL were
were removed from the tumble-polishing machine at different times. obtained at three magnifications: x25 or x100, x300 and x1,000. The
To evaluate the optic edges, standardised SEM pictures with an first two magnifications were used to document the overall orientation
enlargement of x500 were taken of one IOL in each group. A digital of the specimen and the x1,000 magnification photographs were used
computer system (Evaluation of Posterior Capsule Opacification for the microedge analysis. The SEM photographs of each IOL were
System [EPCO] 2000 program) was used to evaluate the area above saved as high-resolution JPEG files. They were then imported into the
the edges on the SEM photographs. To achieve this, the area had to AutoCAD LT 2000 system (Autodesk). This program, which is commonly
be defined as the deviation from an ideal square. The edge’s ability used in engineering and architecture, allows accurate area
to stop cell growth was evaluated by placing each IOL into cell culture calculations. The first step was to adjust the scale of the photograph
74 © TOUCH BRIEFINGS 2009
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