Intraocular Lenses Doğan Gidon

Overview Biological Challange The Eye and Cataracts Restrictions and Design Constraints Materials Polymeric: PMMA, Silicone, Polyacrylic Ocular Problems Accomodation Surgical and Biological Problems Capsule Opacification Light Adjusting Lenses

The Eye Lens comes within the capule, divides anterior and posterior chambers – keeps two bodies separate http://www.nikonlenswear.ca/en/Eye_Chart.php

Cataracts Biological lens is useless – opacification Removal of the lens (and possibly capsule) Hard to correct vision post-lens removal Thick spectacles – magnification of image Problems with single eye cataracts Poor vision restoration Solution – Intraocular Lens (IOLs) Patel, A. S. (2004). Intraocular Implants: A Scientific Perspective. In B. D. Ratner, Biomaterials Science (pp. 591-600). San Diego: Elsevier Academic Press.

Constraints on the Lens Mimicking the natural lens The lens should be Transparent Durable over extended periods of time Non-reactive (biocompatible) Flexible (vs Rigid) Fixed (or controlled motion) Processable (proper curvature) Non adhesive for cells and bacteria (hydrophobic or low water content) Able to restore vision (and correct preexisting refractive problems) Able to withstand optical traumas (eye rubbing etc.) UV blocking (restore biological visual spectrum) Polymeric Materials!

Constraints on the Eye Minimal eye disturbance – small incisions overcoming two boundaries Better delivery systems and smart materials Minimal physical contact with the lens – mechanical disturbance Location of the IOL Low and non-disturbing reaction Prevention of opacification Surgical constraints State of the biological lens, lens capsule and adjacent bodies

IOL Design – Location, Location, Location Where to put the IOL? Phakic eye: Eye with biological lens Aphakic eye: Eye with removed biological lens Pseudophakic eye: Eye with implanted IOL IOLs can be used on phakic and aphackic eyes State of the capsule is important and changes design No capsular bag: Posterior chamber fixation to ciliary body IOL placement with Capsular bag intact Patel, A. S. (2004). Intraocular Implants: A Scientific Perspective. In B. D. Ratner, Biomaterials Science (pp. 591-600). San Diego: Elsevier Academic Press.

IOL Design Shape Haptic – The supporting extensions on the lens Optic – the polymeric refractive material that constitutes the lens Available in singe piece of three piece designs – fixation location and material properties determine the structure Patel, A. S. (2004). Intraocular Implants: A Scientific Perspective. In B. D. Ratner, Biomaterials Science (pp. 591-600). San Diego: Elsevier Academic Press.

IOL materials PMMA First IOLs Rigid Delivery problem large incision (about 6mm) => surgical astigmatism Available in single piece design Good fixation Cheap Poor biocompatibility – more incidences of postoperative reactions Surface treatment for better performance Chehade, M. (1997). lntraocular lens materials and styles: A review. Australian and New Zealand Journal of Ophthalmology (25), 255-263 Werner, L. (2008). Biocompatibility of intraocular lens materials. Current Opinion in Ophthalmology (19), 41-49.

IOL materials Foldable Hydrophobic Polyacrylates Different copolymer acrylics AcrylSof: Copolymer of Phenylethy acrylate and phenylethyl methacrlyate Flexible Smaller surgical incision – foldable/injectable Weaker then PMMA Available in three piece and single piece design Widely used Chehade, M. (1997). lntraocular lens materials and styles: A review. Australian and New Zealand Journal of Ophthalmology (25), 255-263 Werner, L. (2008). Biocompatibility of intraocular lens materials. Current Opinion in Ophthalmology (19), 41-49.

IOL materials Hydrophilic hydrogels Silicone Poly(HEMA) copolymerized with acrylic monomers Not widely used due to post operative complications Silicone Materials such as poly(dimethyl siloxane) Foldable and soft Can only support plate haptics Controversial data on post operative complications Chehade, M. (1997). lntraocular lens materials and styles: A review. Australian and New Zealand Journal of Ophthalmology (25), 255-263 Werner, L. (2008). Biocompatibility of intraocular lens materials. Current Opinion in Ophthalmology (19), 41-49.

Comparison Chehade, M. (1997). lntraocular lens materials and styles: A review. Australian and New Zealand Journal of Ophthalmology (25), 255-263

Ocular Problems The biological lens changes shape to accommodate far and near images Property removed with introduction of IOLs Spectacle dependence Challenge to restore visual accommodation Monovision: differential correction of the two eyes – one near one far adjusted High patient variability in results Menapace, R. (2007). Accommodating intraocular lenses: a critical review of present and future concepts . Graefe’s Arch Clin Exp Ophthalmol (245), 473–489

Multifocal IOLs Multiple Foci on the lens Simultaneous distance and far correction Two superimposed images one in focus and one out of focus Reported discomfort in patients Halos especially at night decreased contrast sensitivity due to light distribution Reported increased spectacle independence Expectation management lead to increased satisfaction – high patient variability Bellucci, R. (2005). Multifocal intraocular lenses. Current Opinion in Ophthalmology (16), 33–37.

Multifocal IOLs Bellucci, R. (2005). Multifocal intraocular lenses. Current Opinion in Ophthalmology (16), 33–37.

Accommodating IOLs Aim for true restoration of accommodation through active or passive movement or shape change of the lens with external stimuli Designed to respond to ciliary muscle contraction Contradictory results – studies found them to be statistically not better than existing designs Company led studies criticized for methodology errors Capsular fibrosis – decreases elasticity and function High patient variability Doane, J. F. (2004). Accommodating intraocular lenses. Current Opinion in Ophthalmology (15), 16-21.

Accommodating IOLs Doane, J. F. (2004). Accommodating intraocular lenses. Current Opinion in Ophthalmology (15), 16-21. http://www.mastereyeassociates.com/lens-implants---premium-iols/

Accommodating IOLs Active responsive systems Mostly conceptual Magnet driven Two lens systems (Dual optic) Smart Lenses – Lens refilling Temperature responsive hydrogel to fill the lens capsule Mostly conceptual Poor clinical results High foreign body reaction – not very biocompatible Doane, J. F. (2004). Accommodating intraocular lenses. Current Opinion in Ophthalmology (15), 16-21.

Accommodating IOLs Doane, J. F. (2004). Accommodating intraocular lenses. Current Opinion in Ophthalmology (15), 16-21.

Accommodating IOLs Doane, J. F. (2004). Accommodating intraocular lenses. Current Opinion in Ophthalmology (15), 16-21.

Surgical and Biological Problems Posterior Capsule Opacification Migration of Lens Epithelial Cells (LECs) Proliferation and differentiation of LECs to pearls or fibroblastic cells Most common problem – secondary cataract Geometry and material are important Hydrophobic acrylic < silicone < PMMA Adhesion of capsule to the lens – no space no cells Square edged lenses prevent cell migration Single piece lenses perform better – no secondary interface Treated with Nd: YAG Laser capsulectomy Werner, L. (2008). Biocompatibility of intraocular lens materials. Current Opinion in Ophthalmology (19), 41-49 Hollick, E. J. (1998). Lens epithelial cell regression on the posterior capsule with diVerent intraocular lens materials . Br J Ophthalmol (82), 1182–1188. .

Surgical and Biological Problems Anterior Capsule Opacification Problem for accomodating IOLs Contact with anterior capsule Problem esp. with silicone Interlenticular Opacifiation Dual optic systems Problem for accomodationg IOLs Werner, L. (2008). Biocompatibility of intraocular lens materials. Current Opinion in Ophthalmology (19), 41-49

Surgical and Biological Problems Bacterial Contamination and infection Esp. with polypropylene haptics Lens malposition Asymmetric capsulorhexis Surgical skill Lens detachment Pigment dispersion Anterior implants – Iris contact Corneal disruption Carlson, A. N. (1998). Intraocular Lens Complications Requiring Removal or Exchange . Survey of Ophtalmology , 42 (4), 417-440.

Light Adjustable IOLs (LALs) Silicone based IOLs (also polyacrylic prototype) Implanted not completely polymerized UV Photo polymerization in situ to change the shape and power and character of the lens (inc. toric or multifocal) Creating a gradient and provoke diffusion Development of a light delivery device for precise manipulation Precise power adjustment for complex situations– esp for patients who underwent refractive laser surgery Allows trial periods for monovision or bifocal type IOLs Maloney, R. (2003, Jan). The Changing Shape of Customized IOLs. Review of Ophtalmology , 44-45. Schwartz, D. M. (2003;). Light-Adjustable Lens. Trans Am Ophthalmol Soc (101), 411-430.

Light Adjustable IOLs (LALs) Maloney, R. (2003, Jan). The Changing Shape of Customized IOLs. Review of Ophtalmology , 44-45.

Conclusion Positive outcome is dependent on Patient Surgical skill Managed expectations appropriate IOL selection for situation Surgical skill Small incisions No bacterial contamination or malposition IOL material Preventive of PCO Novel materials to improve spectacle independence and restore natural visual acuty

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