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Intraocular lenses inmodern cataract surgery

Khiun Tjia
9 June, 2014  
All healthcare systems today are focused on reducing wastage, cutting costs and becoming more efficient and using AcrySof® intraocular lenses can help in attaining those goals
 
Khiun Tjia MD
Anterior Segment Specialist,
Isala Clinics, Zwolle, 
The Netherlands
 
A cataract is a clouding of the clear crystalline lens in the eye and is one of the leading causes of vision impairment, accounting for 33% of visual impairment cases and 51% of blindness cases worldwide according to the World Health Organization.(1)
 
Cataracts most commonly occur in older people and lead to a gradual deterioration in vision, as light is obscured passing through the eye’s natural lens. The condition usually affects both eyes, but almost always one eye is affected earlier than the other. Cataracts are responsible for an estimated 16 million cases of blindness globally.(2,3)
 
Because most cataracts are part of the normal ageing process, they cannot be reversed or treated with medications or eye drops. They can, however, be successfully treated by surgery, in which the opacified lens is removed and replaced with a clear artificial lens implant, called an intraocular lens or IOL.
 
The increase in the prevalence of cataracts and vision impairment among an ageing population has significant economic implications for healthcare systems everywhere. The global cost of vision loss has been estimated at €2.2trillion, with cataracts accounting for a large percentage of that figure.(4) In Europe, the estimated loss of gross domestic product due to uncorrected refractive error, for a four-year period, has been estimated at over €30,000million.(5) 
 
The good news, however, is that cataract surgery is one of the most cost-effective surgical procedures to address vision problems.(6,7) The operation is considerably cheaper in Europe compared with the US and is affordable in many developing countries.
 
Traditional IOLs used in cataract replacement surgery are usually monofocal lenses, which have equal power in all regions of the lens and are in sharpest focus at only one distance. They do not, however, correct pre-existing astigmatism, a result of irregular corneal shape that distorts vision at all distances.
 
Most patients who have had monofocal intraocular lenses implanted usually require reading glasses. Other IOL options include toric IOLs to treat pre-existing corneal astigmatism and multifocal IOLs, which seek to provide a high quality of vision at all distances. 
 
Tried-and-trusted IOL platform
As a cataract surgeon in a busy practice, my choice of intraocular lens is guided by the need to provide my patients with the best possible quality of postoperative vision using material that is well-tolerated, effective and proven over the long term. The AcrySof® range of IOLs (Alcon Laboratories, Inc, Fort Worth, Texas) meets those criteria, with over 75 million AcrySof® lenses now implanted worldwide.(8–13)
 
The success of the AcrySof platform is based on quality design and reliable performance. The hydrophobic acrylic material of AcrySof® lenses offers better biocompatibility than silicone IOLs13 and provides superior bio-adhesion to the capsular bag, resulting in very good rotational stability and low posterior capsule opacification (PCO) rates.(15,16)
 
The AcrySof® IOL material has a very high index of refraction, which makes it suitable for modern micro-incision cataract surgery through 2.2mm or 2.4mm incisions. 
 
Another strong point of the AcrySof® IOL platform is the L-shaped STABLEFORCE® haptic design, which guarantees stable lens positioning for a wide range of capsular bag sizes and minimises compression forces in order to reduce bag stretch and striae in the lens capsule.(17) Such reliable positioning and stability in the eye is critical to ensuring the predictability of the final refractive result. 
 
The long-term stability of the AcrySof® lens in the anterior chamber is not just reassuring from the perspective of safety, but potentially helps to facilitate quicker visual rehabilitation and earlier spectacle prescriptions for the patient.(18) 
 
Safety is also enhanced by the combination of ultraviolet and blue-light filtering properties incorporated into the AcrySof® range of IOLs. This chromophore filter helps to provide protection from the damaging effects of UV and blue light, which some studies have linked with age-related macular degeneration, uveal melanoma and other ocular pathologies.(19,20)
 
Furthermore, the filters may also help to improve night vision in the presence of glare.21 The yellow chromophore of the AcrySof® Natural® IOLs provides patients the natural colour perception they were used to from the age of 30 years onwards, which, in my opinion, is a much more logical choice than non-chromophore materials, which result in a strange bluish colour perception.
 
Ease of use
From a surgical perspective, one of the more appreciable aspects of using the AcrySof® IOL platform is its ease of use. The IOLs are easy and consistent to implant, using either the MONARCH® delivery systems or the automated delivery system INTREPID® Autosert®.
 
MONARCH® cartridges are assembled on the injector, which can be either the MONARCH® IOL manual injector or the newer AutoSert® automatic injection system, which allows a consistent control of IOL delivery through single-hand activation for enhanced wound integrity(22) and enables the surgeon to stay focused on the cataract procedure. 
 
In contrast to silicone IOLs that open almost immediately upon their release from the injector system, the AcrySof® single-piece IOL opens gradually in the eye, providing time for proper positioning of the lens and increasing the safety of the delivery system. The slow unfolding process also means that the surgeon can reposition the lens if required without putting additional pressure or stress on the capsule or zonules.
 
The ease of implantation is greatly enhanced by Alcon’s bespoke MONARCH® IOL delivery system combining a reusable handpiece and a sterile single-use cartridge. The advanced design enables the surgeon to view and verify lens orientation throughout the implantation process. Simplified loading, controlled consistent delivery and ease of implantation are the main benefits delivered by the MONARCH® IOL delivery system.
 
Designed to enable safe and efficient IOL delivery into the eye, the MONARCH® cartridges allow the surgeon to implant the IOL using their preferred incision size. Today’s trend is moving towards micro-incision (2.2mm) and lower, in which the MONARCH® D cartridge plays an important role.
 
Size is not everything
For many surgeons today, the combination of Alcon’s OZil® Torsional ultrasound phacoemulsification and micro-coaxial cataract surgery through a 2.2–2.4mm incision represents the optimal surgical approach, since it involves little or no learning curve, less incision leakage, less need for newer instrumentation and excellent visual outcomes.
 
While the increasing popularity of Advanced Technology toric and multifocal IOLs is undoubtedly driving a trend towards ever-smaller incisions, there is an important balance to be struck between incision size and wound architecture.
 
A study(23) we conducted some years ago demonstrated that a 2.2mm incision with MONARCH® D cartridge induces minimal stress on the wound and allows for smooth implantation of an Advanced Technology IOL. The key point is that, while incision size is important, it should not be achieved at the expense of overall wound architecture.
 
Taking the sting out of astigmatism
Patients today expect spectacle independence after their cataract surgery and we know from a number of large population-based studies that about 40% of patients presenting for surgery have significant astigmatism.(24) We also know that a toric lens implant is more predictable and more stable than corneal incision surgery and will not induce the higher-order aberrations that corneal incisions may induce.
 
The ideal astigmatism treatment is precise and accurate with predictable outcomes. For patients with significant corneal astigmatism, the AcrySof® Toric range of lenses gives surgeons the opportunity to kill two birds with one stone, improving their patients’ vision with cataract surgery while at the same time neutralising their astigmatism.
 
With an overall length of 13mm and an optic diameter of 6mm, the lens of the AcrySof® Toric IOL is convex on both sides, enabling it to provide both spherical and astigmatic correction. The IOL’s toricity is generated on the posterior surface of the lens while the aspherical anterior surface provides correction of spherical aberration allowing micro-coaxial cataract surgery through a 2.2–2.4mm incision.
 
The adoption of toric IOLs requires only minor modifications to standard IOL implantation process. The AcrySof® Toric IOL platform provides the opportunity for patients with astigmatism to achieve excellent uncorrected distance vision and resulting spectacle independence. In a study(17) in the US, over 90% of patients implanted with the AcrySof® Toric IOL achieved distance vision spectacle independence compared to 50% with a monofocal lens.
 
A cost-effective IOL platform
All healthcare systems today are focused on reducing wastage, cutting costs and becoming more efficient. Using AcrySof® IOLs can help in attaining those goals, as these lenses limit the need for secondary surgery due to complications compared with traditional and competitor IOLs. Lower rates of posterior capsule opacification (PCO) have been observed with these hydrophobic lenses than with hydrophylic acrylic or silicone materials.(25–28)
 
Lower incidences of PCO are also associated with lower rates of secondary hospital admissions, including fewer Nd:YAG laser treatments, than with other IOL designs.(29,30) The bottom line is that the lower rate of postoperative complications with the AcrySof® lenses is associated with reduced costs.(28)
 
The use of AcrySof® Advanced Technology IOLs in the form of premium lenses also leads to reduced numbers of healthcare contacts and a reduced need for glasses.(31,32) Studies in several European countries underscore the fact that reductions in the need for glasses from premium IOL implantation results in lower costs compared with monofocal IOLs.(32–36)
 
The majority of patients are willing to pay to be free of spectacles, with about 80% who wore spectacles before cataract surgery willing to pay at least €0.5/day to be spectacle-free.(37) Up to 85% of patients would be willing to pay for advanced technology IOLs with some level of co-payment.38 Reduced dependence on spectacles resulting from the use of IOLs will reduce the number of visits for spectacle prescriptions, ultimately resulting in reduced costs to the payer. 
 
In countries with co-payment, the cost to the payer for Advanced Technology IOLs is the same as for standard lenses because patients will pay for the difference in cost between a basic monofocal IOL and an advanced technology IOL themselves. 
 
The Dutch healthcare system, for instance, does not cover the extra expense of toric and multifocal IOLs. Although the regulatory framework governing co-payment for Advanced Technology IOLs has not yet been clearly defined, out-of pocket payments to cover additional costs are increasingly accepted by the authorities. The co-payment price varies from centre to centre. 
 
Conclusions
Not all IOL materials are created equal. AcrySof® advanced technology IOLs provide vision-correcting options to allow a broad range of patients with differing requirements to reduce their dependence on spectacles. For a cataract surgeon, having access to a full range of refractive powers and optical options on one IOL platform is reassuring because I have confidence in the performance and predictability of these lenses.
 
References
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  23. Tjia K. Presentation given at a meeting of European INFINITI® Vision System users held in Maidenhead, United Kingdom;15–16 March 2008.
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  27. Stordahl PB, Drolsum L. A comparison of Nd:YAG capsulotomy rate in two different intraocular lenses: AcrySof and Stabibag. Acta Ophthalmol Scand 2003;81:326–30. 
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  29. Apple DJ 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;108:505–18. 
  30. Boureau C et al. Incidence of Nd:YAG laser capsulotomies after cataract surgery: comparison of 3 square-edged lenses of different composition. Can J Ophthalmol 2009;44:165–70.
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  37. Cuq C et al. A European survey of patient satisfaction with spectacles after cataract surgery and the associated costs in four European countries (France, Germany, Spain, and Italy). Ophthalmic Epidemiol 2008;15:234–41.
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