Comparison of artificial lenses placed in eyes with uveitis during cataract surgery

Background

Cataract, a cloudy lens within the eye, is a major complication in people with uveitis (inflammation of the middle layer of the eye). Different types of artificial lenses (intraocular lenses, IOLs) are available to insert into the eye after removal of the cloudy natural lens during cataract surgery. The purpose of this review is to summarize the effects of different artificial lenses in adults with uveitis.

Study characteristics

The review authors searched the medical literature up to August 2013 and identified four randomized controlled trials (clinical studies where people are randomly put into one of two or more treatment groups) containing 216 participants investigating different lens types. Lens materials studied were acrylic, silicone, heparin surface modified, and poly(methyl methacrylate). The trials included participants with different causes of uveitis, compared different lens types, and reported different outcomes. Due to these differences across trials, no meta-analysis (pooling of trial data) was performed. The largest trial (140 participants) was funded by a professional society. The other three trials did not report their funding sources.

Key results

There is very limited evidence on which to determine the effects of different types of lens materials for people with uveitis. The results from the largest trial provide only preliminary evidence that acrylic lenses may perform better than silicone lenses in terms of improving vision and reducing the chances of post-surgical inflammation and complications. At this time, there is not enough data to conclude whether additional types of lenses are preferable to other types.

Quality of the evidence

Because the trials included small numbers of participants in each of the four lens-type groups, there is uncertainty in the results of the studies.

Authors' conclusions: 

Based on the trials identified in this review, there is uncertainty as to which type of IOL provides the best visual and clinical outcomes in people with uveitis undergoing cataract surgery. The studies were small, not all lens materials were compared in all studies, and not all lens materials were available in all study sites. Evidence of a superior effect of hydrophobic acrylic lenses over silicone lenses, specifically for posterior synechiae outcomes comes from a single study at a high risk of performance and detection bias. However, due to small sample sizes and heterogeneity in outcome reporting, we found insufficient information to assess these and other types of IOL materials for cataract surgery for eyes with uveitis.

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Background: 

Cataract formation often occurs in people with uveitis. It is unclear which intraocular lens (IOL) type is optimal for use in cataract surgery for eyes with uveitis.

Objectives: 

To summarize the effects of different IOLs on visual acuity, other visual outcomes, and quality of life in people with uveitis.

Search strategy: 

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 7), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to August 2013), EMBASE (January 1980 to August 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to August 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrials.gov) and the WHO International Clinical Trials Registry Platform (ICTRP) (www.who.int/ictrp/search/en). We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 14 August 2013. We also performed forward and backward searching using the Science Citation Index and the reference lists of the included studies, respectively, in August 2013.

Selection criteria: 

We included randomized controlled trials (RCTs) comparing hydrophobic or hydrophilic acrylic, silicone, or poly(methyl methacrylate) (PMMA) IOLs with or without heparin-surface modification (HSM), with each other, or with no treatment in adults with uveitis, for any indication, undergoing cataract surgery.

Data collection and analysis: 

We used standard methodological procedures expected by The Cochrane Collaboration. Two review authors screened the search results and for included studies, assessed the risk of bias and extracted data independently. We contacted study investigators for additional information. We did not perform a meta-analysis due to variability in reporting and follow-up intervals for the primary and secondary outcomes of interest.

Main results: 

We included four RCTs involving 216 participants (range of 2 to 140 participants with uveitic cataract per trial) and comparing up to four types of IOLs. The largest study was an international study with centers in Brazil, Egypt, Finland, France, Japan, the Netherlands, Slovak Republic, Spain, and the USA; two studies were conducted in Germany and one in Saudi Arabia. There was substantial heterogeneity with respect to the ages of participants and etiologies of uveitis within and across studies. The length of follow-up among the studies ranged from 1 to 24 months after cataract surgery. The studies were at low risk of selection bias, but two of the four studies did not employ masking and only one study included all randomized participants in the final analyses. The funding source was disclosed by investigators of the largest study (professional society) and not reported by the other three. Due to heterogeneity in lens types evaluated and outcomes reported among the trials, we did not combine data in a meta-analysis.

In the largest study (140 participants), the study eye of each participant was randomized to receive one of four types of IOLs: hydrophobic acrylic, silicone, HSM PMMA, or unmodified PMMA. Proportions of participants with one or more Snellen lines of visual improvement were similar among the four treatment groups at one year' follow-up: 45 of 48 (94%) in the hydrophobic acrylic IOL group, 39 of 44 (89%) in the silicone IOL group, 18 of 22 (82%) in the HSM PMMA IOL group, and 22 of 26 (85%) in the unmodified PMMA IOL group. When comparing hydrophobic acrylic IOLs with silicone IOLs, the risk ratio (RR) was 1.06 (95% confidence interval (CI) 0.93 to 1.20). At one year' follow-up, fewer eyes randomized to hydrophobic acrylic IOLs developed posterior synechiae when compared with eyes receiving silicone IOLs (RR 0.18, 95% CI 0.04 to 0.79); the effects between these groups were less certain with respect to developing posterior capsule opacification (PCO) (RR 0.74, 95% CI 0.41 to 1.37), corneal edema (RR 0.49, 95% CI 0.22 to 1.12), cystoid macular edema (RR 0.10, 95% CI 0.01 to 1.84), or mild IOL decentration (RR 0.92, 95% CI 0.06 to 14.22).

Two intra-individual studies also compared HSM PMMA IOLs with unmodified PMMA IOLs at three or six months of follow-up. These studies, including a combined total of 16 participants with uveitis, were insufficiently powered to detect differences in outcomes among eyes of people with uveitis randomized to receive HSM PMMA IOLs when compared with fellow eyes receiving unmodified PMMA IOLs.

In the fourth study (60 participants), the study eye of each participant was randomized to receive a hydrophobic or hydrophilic acrylic IOL. At three months, there were no statistical or clinical differences between hydrophobic and hydrophilic acrylic IOL types in the proportions of participants with two or more Snellen lines of visual improvement (RR 1.03, 95% CI 0.87 to 1.22). There were similar rates in the development of PCO between hydrophobic or hydrophilic acrylic IOLs at six months' follow-up (RR 1.00, 95% CI 0.80 to 1.25). The effect of the lenses on posterior synechiae was uncertain at six months' follow-up (RR 0.50, 95% CI 0.05 to 5.22).

None of the included studies reported quality of life outcomes.

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