Werner_edit_Layout 1 22/01/2010 11:03 Page 76
Anterior Segment Intraocular Lens
Different prototypes were sent to the BERI for evaluation following the interesting in light of some clinical studies comparing square-edged
same protocol described above (see Figure 2). The area deviating from IOLs manufactured from different materials and reporting higher rates
a perfect square of the current Hoya AF-1 family measured 39.1µ
2
. This of PCO with hydrophilic acrylic lenses.
11–15
In many instances the
is the lowest value measured among currently available hydrophobic authors concluded that this was related to a ‘material’ effect;
acrylic lenses and therefore the most square of all. The edge surface however, the edges of the lenses included were perhaps just not
characteristics of the lenses remained unchanged, i.e. the surfaces comparable. Our study confirms that all square edges in the market
are smooth and regular. The IOLs with the optimised edge profile are are not the same, and perhaps large variations in edge profile may
currently under clinical investigation. The modified square edge is account for differences in clinical outcomes of post-operative PCO.
commercially available in selected countries for the new AF-1 models
iSymm aspheric and iMics Microincision lenses. Conclusions
In summary, analysis of the microstructure of the optic edge of
Other Edge Profile Studies currently available square-edge IOLs revealed a large variation of the
Nanavaty et al. performed an SEM study comparing the edge deviation area from a perfect square, as well as mean values that
profile of commercially available square-edged IOLs.
10
Their study were higher for hydrophilic acrylic lenses in comparison with values
included a total of 17 square-edged designs of +20.0D, with five reported for hydrophobic acrylic and silicone lenses. Only existing and
hydrophobic acrylic, seven hydrophilic acrylic and five silicone lenses. future clinical data will help us better understand the effect of
Perpendicular images with a magnification of x500 were obtained and microedge structure and design on reducing PCO, but perhaps a
analysed using purpose-designed software to produce a line tracing cut-off value to clinically label an IOL as square-edged should be
of the edge profile of the lenses. The sharpness of the edge profile sought. The methodology used in such studies can help optimise the
was then quantified by measuring the local radius of curvature at the edge profile of IOLs. n
point on the posterior edge with the smallest radius. Their conclusions
are similar to ours in that as a group, hydrophilic acrylic lenses
appeared to have relatively rounder edges compared with
Liliana Werner is an Associate Professor of
Ophthalmology and Co-Director of the Intermountain
hydrophobic acrylic and silicone lenses. This is probably due to the
Ocular Research Center at the John A Moran Eye
manufacturing process of hydrophilic acrylic lenses, which involves
Center, University of Utah. Between 2006 and 2008 she
being lathe-cut from dehydrated blocks that are then re-hydrated.
was Director of Pre-clinical Research at the Berlin Eye
Research Institute. She is the 2003 Research to Prevent
Water absorption by the IOL material may render the final aspect of
Blindness Olga Keith Wiess Scholar awardee, a member
the edge rounder as the IOL swells.
of the Editorial Board of the Journal of Cataract and
Refractive Surgery and EyeWorld, a member of the
International Intra-Ocular Implant Club, a member of the Continuing Medical Education
Clinical Significance
Advisory Committee of the American Society of Cataract and Refractive Surgery
The factor that may play the most important clinical role in evening
(ASCRS) and a member of the Cataract Subcommittee of the American Academy of
out the differences in the microedge profiles observed in our study is
Ophthalmology (AAO) Annual Meeting Programme Committee. She has authored more
than 250 peer-reviewed articles and chapters on the subject of intraocular lenses and
shrink-wrapping of the IOL by the capsular bag, which enhances
other ocular implantable biodevices and has received numerous awards for her
contact between the posterior IOL surface and the posterior capsule.
scientific work in international meetings around the world. Dr Werner has an MD from
However, this factor may not even out large differences in edge
Brazil and a PhD (biomaterials) from France.
profile. The results of all of the above-mentioned studies are
1. Schauersberger J, Amon M, Kruger A, et al. Comparison of of intraocular lenses: Part 1: Influence of optic design on capsule opacification after implantation of a hydrophilic or
the biocompatibility of two foldable intraocular lenses the growth of the lens epithelial cells in vitro, J Cataract a hydrophobic acrylic intraocular lens: one-year follow-up,
with sharp optic edges, J Cataract Refract Surg, 2001;27: Refract Surg, 2005;31:2172–9. J Cataract Refract Surg, 2006;32:1627–31.
1579–85. 7. Werner L, Müller M, Tetz M, Evaluating and defining the 12. Kugelberg M, Wejde G, Jayaram H, Zetterström C, Two-year
2. Buehl W, Findl O, Menapace R, et al., Effect of an acrylic sharpness of intraocular lenses. Microedge structure of follow-up of posterior capsule opacification after
intraocular lens with a sharp posterior optic edge on commercially available square-edged hydrophobic lenses, implantation of a hydrophilic or hydrophobic acrylic
posterior capsule opacification, J Cataract Refract Surg, J Cataract Refract Surg, 2008;34:310–17. intraocular lens, Acta Ophthalmol, 2008;86(5):533–6.
2002;28:1105–11. 8. Werner L, Tetz M, Feldmann I, Bücker M, Evaluating and 13. Richter-Mueksch S, et al., Uveal and capsular
3. Prosdocimo G, Tassinari G, Sala M, et al., Posterior capsule defining the sharpness of intraocular lenses. Microedge biocompatibility after implantation of sharp-edged
opacification after phacoemulsification: silicone CeeOn structure of commercially available square-edged hydrophilic acrylic, hydrophobic acrylic, and silicone
Edge versus acrylate AcrySof intraocular lens, J Cataract hydrophilic lenses, J Cataract Refract Surg, 2009;35:556–66. intraocular lenses in eyes with pseudoexfoliation
Refract Surg, 2003;29:1551–5. 9. Hancox J, Spalton DJ, Cleary G, et al., Fellow-eye syndrome, J Cataract Refract Surg, 2007;33:1414–18.
4. Kohnen T, Maqdowski G, Koch DD, Scaning electron comparison of posterior capsule opacification with 14. Cheng JW, et al., Efficacy of different intraocular lens
microscopic analysis of foldable acrylic and hydrogel AcrySof SN60AT and AF-1 YA-60BB blue-blocking materials and optic edge designs in preventing posterior
intraocular lenses, J Cataract Refract Surg, 1996;22:1342–50. intraocular lenses, J Cataract Refract Surg, 2008;34: capsular opacification: a meta-analysis, Am J Ophthalmol,
5. Mencucci R, Ponchietti C, Nocentini L, et al., Scanning 1489–94. 2007;143:428–36.
electron microscopic analysis of acrylic intraocular lenses 10. Nanavaty MA, Spalton DJ, Boyce J, et al., Edge profile of 15. Heatley CJ, Spalton DJ, Kumar A, et al., Comparison of
for microincision cataract surgery, J Cataract Refract Surg, commercially available square-edged intraocular lenses, posterior capsule opacification rates between hydrophilic
2006;32:318–23. J Cataract Refract Surg, 2008;34:677–86. and hydrophobic single-piece acrylic intraocular lenses,
6. Tetz M, Wildeck A, Evaluating and defining the sharpness 11. Kugelberg M, Wejde G, Jayaram H, Zetterström C, Posterior J Cataract Refract Surg, 2005;31:718–24.
76 EUROPEAN OPHTHALMIC REVIEW
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