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JOURNAL ARTICLE

Intraocular lenses for the treatment of age-related cataracts: an evidence-based analysis

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Ontario Health Technology Assessment Series 2009, 9 (15): 1-62
23074519

OBJECTIVE: The objective of the report is to examine the comparative effectiveness and cost-effectiveness of various intraocular lenses (IOLs) for the treatment of age-related cataracts.

CLINICAL NEED: TARGET POPULATION AND CONDITION A cataract is a hardening and clouding of the normally transparent crystalline lens that may result in a progressive loss of vision depending on its size, location and density. The condition is typically bilateral, seriously compromises visual acuity and contrast sensitivity and increases glare. Cataracts can also affect people at any age, however, they usually occur as a part of the natural aging process. The occurrence of cataracts increases with age from about 12% at age 50 years, to 60% at age 70. In general, approximately 50% of people 65 year of age or older have cataracts. Mild cataracts can be treated with a change in prescription glasses, while more serious symptoms are treated by surgical removal of the cataract and implantation of an IOL. In Ontario, the estimated prevalence of cataracts increased from 697,000 in 1992 to 947,000 in 2004 (35.9% increase, 2.4% annual increase). The number of cataract surgeries per 1,000 individuals at risk of cataract increased from 64.6 in 1992 to 140.4 in 1997 (61.9% increase, 10.1% annual increase) and continued to steadily increase to 115.7 in 2004 (10.7% increase, 5.2% increase per year).

DESCRIPTION OF TECHNOLOGY/THERAPY: IOLs are classified either as monofocal, multifocal, or accommodative. Traditionally, monofocal (i.e.. fixed focusing power) IOLs are available as replacement lenses but their implantation can cause a loss of the eye's accommodative capability (which allows variable focusing). Patients thus usually require eyeglasses after surgery for reading and near vision tasks. Multifocal IOLs aim to improve near and distant vision and obviate the need for glasses. Potential disadvantages include reduced contrast sensitivity, halos around lights and glare. Accommodating IOLs are designed to move with ciliary body contraction during accommodation and, therefore, offer a continuous range of vision (i.e. near, intermediate and distant vision) without the need for glasses. Purported advantages over multifocal IOLs include the avoidance of haloes and no reduction in contrast sensitivity. Polymethyl methacrylate (PMMA) was the first material used in the fabrication of IOLs and has inherent ultraviolet blocking abilities. PMMA IOLs are inflexible, however, and require a larger incision for implantation compared with newer foldable silicone (hydrophobic) and acrylic (hydrophobic or hydrophilic) lenses. IOLs can be further sub-classified as being either aspheric or spheric, blue/violet filtered or non-filtered or 1- or 3-piece. METHODS OF EVIDENCE-BASED ANALYSIS: A literature search was conducted from January 2003 to January 2009 that included OVID MEDLINE, MEDLINE In-Process and Other Non-Indexed Citations, EMBASE, the Cumulative Index to Nursing & Allied Health Literature (CINAHL), The Cochrane Library, and the International Agency for Health Technology Assessment/Centre for Review and Dissemination. Inclusion CriteriaExclusion Criteriaadult patients with age-related cataractssystematic reviews, randomized controlled trials (RCTs)

PRIMARY OUTCOMES: distance visual acuity (best corrected distance visual acuity), near visual acuity (best distance corrected near visual acuity)

SECONDARY OUTCOMES: contrast sensitivity, depth of field, glare, quality of life, visual function, spectacle dependence, posterior capsule opacification.studies with fewer than 20 eyesIOLs for non-age related cataractsIOLs for presbyopiastudies with a mean follow-up <6monthsstudies reporting insufficient data for analysis COMPARISONS OF INTEREST: The primary comparison of interest was accommodative vs. multifocal vs. monofocal lenses. Secondary comparisons of interest included: tinted vs. non-tinted lensesaspheric vs. spheric lensesmultipiece vs. single piece lensesbiomaterial A (e.g. acrylic) vs. biomaterial B (e.g. silicone) lensessharp vs. round edged lensesThe quality of the studies was examined according to the GRADE Working Group criteria for grading quality of evidence for interventional procedures.

SUMMARY OF FINDINGS: The conclusions of the systematic review of IOLs for age-related cataracts are summarized in Executive Summary Table 1. CONSIDERATIONS FOR THE ONTARIO HEALTH SYSTEM: Procedures for crystalline lens removal and IOL insertion are insured and listed in the Ontario Schedule of Benefits.If a particular lens is determined to be medically necessary for a patient, the cost of the lens is covered by the hospital budget. If the patient chooses a lens that has enhanced features, then the hospital may choose to charge an additional amount above the cost of the usual lens offered.An IOL manufacturer stated that monofocal lenses comprise approximately 95% of IOL sales in Ontario and premium lenses (e.g., multifocal/accomodative) consist of about 5% of IOL sales.A medical consultant stated that all types of lenses are currently being used in Ontario (e.g., multifocal, monofocal, accommodative, tinted, nontinted, spheric, and aspheric). Nonfoldable lenses, rarely used in routine cases, are primarily used for complicated cataract implantation situations.ES Table 1:Conclusions for the Systematic Review of IOLs for Age-Related CataractsComparisonConclusionGRADE QualityMultifocal vs. monofocalObjective OutcomesSignificant improvement in BDCUNVANo significant difference in BCDVAInconclusive evidence for contrast sensitivityInconclusive evidence for glareSubjective OutcomesInconclusive evidence for visual satisfactionSignificant increase in glare/halosSignificant increase in freedom from spectaclesmoderatemoderatelowvery lowlowlow/moderatelow/moderateAccommodative vs. multifocal/monofocalInconclusive due to Insufficient limited evidence for any effectiveness outcomevery lowHydrophilic acrylic vs. other materials (hydrophobic acrylic, silicone)Significant increase in PCO scoreLowSharp edged compared to round edgedSignificant reduction in PCO scoreLowOne piece compared to three pieceNo significant difference in PCO scorelowHydrophobic acrylic compared to siliconeNo significant difference in PCO scoremoderateAspherical modified prolate anterior surface compared to sphericalNo significant difference in VASignificant reduction in contrast sensitivityvery lowvery lowBlue light filtering compared to non blue-light filteringNo significant difference in BCDVANo significant difference in contrast sensitivityNo significant difference in HRQLlowlowhigh/moderateBCDVA refers to best corrected distance visual acuity; BDCUNVA, best distance corrected unaided near visual acuity; HRQL, health related quality of life; PCO, posterior capsule opacification; VA, visual acuity.

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