Accommodative intraocular lens versus standard monofocal intraocular lens implantation in cataract surgery: Cochrane systematic review

Abstract

Assessed as up to date: 2013/10/10

Background

Following cataract surgery and intraocular lens (IOL) implantation, loss of accommodation or postoperative presbyopia occurs and remains a challenge. Standard monofocal IOLs correct only distance vision; patients require spectacles for near vision. Accommodative IOLs have been designed to overcome loss of accommodation after cataract surgery.

Objectives

To define (a) the extent to which accommodative IOLs improve unaided near visual function, in comparison with monofocal IOLs; (b) the extent of compromise to unaided distance visual acuity; c) whether a higher rate of additional complications is associated the use of accommodative IOLs.

Search methods

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 9), Ovid MEDLINE, Ovid MEDLINE in-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily Update, Ovid OLDMEDLINE (January 1946 to October 2013), EMBASE (January 1980 to October 2013), Latin American and Caribbean Health Sciences Literature Database (LILACS) (January 1982 to October 2013), the metaRegister of Controlled Trials (mRCT) (www.controlled-trials.com), ClinicalTrials.gov (www.clinicaltrial.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 10 October 2013.

Selection criteria

We include randomised controlled trials (RCTs) which compared implantation of accommodative IOLs to implantation of monofocal IOLs in cataract surgery.

Data collection and analysis

Two authors independently screened search results, assessed risk of bias and extracted data. All included trials used the 1CU accommodative IOL (HumanOptics, Erlangen, Germany) for their intervention group. One trial had an additional arm with the AT-45 Crystalens accommodative IOL (Eyeonics Vision). We performed a separate analysis comparing 1CU and AT-45 IOL.

Main results

We included four RCTs, including 229 participants (256 eyes), conducted in Germany, Italy and the UK. The age range of participants was 21 to 87 years. All studies included people who had bilateral cataracts with no pre-existing ocular pathologies. We judged all studies to be at high risk of performance bias. We graded two studies with high risk of detection bias and one study with high risk of selection bias.

Participants who received the accommodative IOLs achieved better distance-corrected near visual acuity (DCNVA) at six months (mean difference (MD) -3.10 Jaeger units; 95% confidence intervals (CI) -3.36 to -2.83, 2 studies, 106 people, 136 eyes, moderate quality evidence). Better DCNVA was seen in the accommodative lens group at 12 to 18 months in the three trials that reported this time point but considerable heterogeneity of effect was seen, ranging from 1.3 (95% CI 0.98 to 1.68; 20 people, 40 eyes) to 6 (95% CI 4.15 to 7.85; 51 people, 51 eyes) Jaeger units and 0.12 (95% CI 0.05 to 0.19; 40 people, binocular) logMAR improvement (low quality evidence). The relative effect of the lenses on corrected distant visual acuity (CDVA) was less certain. At six months there was a standardised mean difference of -0.04 standard deviations (95% CI -0.37 to 0.30, 2 studies, 106 people, 136 eyes, low quality evidence). At long-term follow-up there was heterogeneity of effect with 18-month data in two studies showing that CDVA was better in the monofocal group (MD 0.12 logMAR; 95% CI 0.07 to 0.16, 2 studies, 70 people,100 eyes) and one study which reported data at 12 months finding similar CDVA in the two groups (-0.02 logMAR units, 95% CI -0.06 to 0.02, 51 people) (low quality evidence).

The relative effect of the lenses on reading speed and spectacle independence was uncertain, The average reading speed was 11.6 words per minute more in the accommodative lens group but the 95% confidence intervals ranged from 12.2 words less to 35.4 words more (1 study, 40 people, low quality evidence). People with accommodative lenses were more likely to be spectacle-independent but the estimate was very uncertain (risk ratio (RR) 8.18; 95% CI 0.47 to 142.62, 1 study, 40 people, very low quality evidence).

More cases of posterior capsule opacification (PCO) were seen in accommodative lenses but the effect of the lenses on PCO was uncertain (Peto odds ratio (OR) 2.12; 95% CI 0.45 to 10.02, 91 people, 2 studies, low quality evidence). People in the accommodative lens group were more likely to require laser capsulotomy (Peto OR 7.96; 95% CI 2.49 to 25.45, 2 studies, 60 people, 80 eyes, low quality evidence). Glare was reported less frequently with accommodative lenses but the relative effect of the lenses on glare was uncertain (RR any glare 0.78; 95% CI 0.32 to 1.90, 1 study, 40 people, and RR moderate/severe glare 0.45; 95% CI 0.04 to 4.60, low quality evidence).

Authors' conclusions

There is moderate-quality evidence that study participants who received accommodative IOLs had a small gain in near visual acuity after six months. There is some evidence that distance visual acuity with accommodative lenses may be worse after 12 months but due to low quality of evidence and heterogeneity of effect, the evidence for this is not clear-cut. People receiving accommodative lenses had more PCO which may be associated with poorer distance vision. However, the effect of the lenses on PCO was uncertain.

Further research is required to improve the understanding of how accommodative IOLs may affect near visual function, and whether they provide any durable gains. Additional trials, with longer follow-up, comparing different accommodative IOLs, multifocal IOLs and monofocal IOLs, would help map out their relative efficacy, and associated late complications. Research is needed on control over capsular fibrosis postimplantation.

Risks of bias, heterogeneity of outcome measures and study designs used, and the dominance of one design of accommodative lens in existing trials (the HumanOptics 1CU) mean that these results should be interpreted with caution. They may not be applicable to other accommodative IOL designs.

Author(s)

Ong Hon Shing, Evans Jennifer R, Allan Bruce DS

Summary

Accommodative intraocular lenses compared with monofocal intraocular lenses in cataract surgery

Background Accommodation is the ability of the eye to focus on both distant and near objects.

Accommodation is achieved through the contraction of ciliary muscles, which results in an increase in curvature and a forward shift of the natural lens in the eye. Accommodation declines with increasing age due to a decrease in lens elasticity and a reduction in ciliary muscle contraction, resulting in difficulty in near vision (presbyopia). This is a problem for most people in their 40s or 50s.

For best optical performance, the lens must be transparent. Cataract is the clouding of the human lens. It is more common with increasing age, and is a common cause of visual impairment. Fortunately, cataract is treatable by a surgical procedure in which the natural lens is removed through a small incision. Once all lens material is removed, an artificial lens, known as an intraocular lens (IOL) is implanted into the eye to lie in the original position of the removed natural lens.

All functions of the natural lens are preserved by an IOL, with the exception of accommodation. Standard IOLs, known as monofocal IOLs, allow only distant objects to be focused and seen clearly. Patients require spectacles for near vision. This problem after cataract surgery remains a challenge for ophthalmologists. To overcome the loss of accommodation after cataract surgery, various strategies have been tried with variable success.

Accommodative IOLs have been designed to restore accommodation. The aim of this systematic review is to help define the extent to which accommodative IOLs improve near vision in comparison with standard monofocal IOLs.

Study characteristics This review looked at four studies that enrolled 229 people (256 eyes) and compared the use of accommodative IOLs to the use of monofocal IOLs in cataract surgery. We last searched for evidence in October 2013.

Key findings The results of the review showed that participants who received accommodative IOLs had improvements in near vision at six months and at 12 months after surgery compared to those who received monofocal IOLs. However, such improvements were small and reduced with time. Low-quality evidence also showed that more than 12 months after surgery, there was a compromise in distance vision for people with accommodative IOLs. This may be related to the finding that those who received accommodative IOLs also appeared to have a higher rate of posterior capsular opacification (thickening and clouding of the tissue behind the IOL). However, these findings were uncertain. Further research on accommodative IOLs is required before we can draw conclusions on their effectiveness and safety compared to monofocal IOLs

Quality of the evidence Overall the quality of the evidence was low or very low with the exception for the findings on near vision at six months.

Reviewer's Conclusions

Implications for practice

This systematic review suggests that implantation of accommodative intraocular lenses (IOLs) in cataract surgery is associated with small gains in near visual acuity (approximately one Snellen line) as well as gains in some measures of accommodative function (moderate quality of evidence). Size of accommodative function appears to reduce with time. Due to low quality of evidence, the relative effect of accommodative lenses on functional outcomes, such as reading speed and spectacle independence, is uncertain.

There is some evidence that distance visual acuity with accommodative lenses may be worse after 12 months, but currently the evidence for this is not clear-cut. This may be associated with more posterior capsular opacification (PCO) in people receiving accommodative lenses (low quality of evidence). However, the effect of the accommodative lenses on PCO is uncertain.

There was a statistically significant reduction in anterior chamber depth on accommodation in participants who received accommodative IOLs compared to those who received monofocal IOLs at six and after 12 months post-treatment. These reductions of anterior chamber depth on accommodation, typically accounted for by an anterior displacement of IOLs, suggest some validity in the focus shift hypothesis for accommodative IOLs. But the clinical relevance of small changes in anterior chamber depth on accommodative effect observed after 12 months is questionable (mean difference 0.21 mm). Earlier modelling suggests that a forward shift in lens position of approximately 10 times this magnitude (2 mm) would be required to produce 3 dioptres of true pseudophakic accommodation.

Heterogeneity of outcome measures and study designs used, plus the dominance of one design of accommodative lens in existing trials (the HumanOptics 1CU) suggest that the results of our analysis should be interpreted with caution, and may not be applicable to other accommodative IOL designs.

Implications for research

Further trials are required for a definitive evaluation of accommodative IOLs. The mechanisms of any effect through which accommodative IOLs improve near visual function is still poorly understood and, as discussed, may be multifactorial. Further research is required to improve the understanding of such accommodative IOLs. It would also be useful to have more long-term outcome data to monitor sustainability of accommodative and near visual functional capacity of accommodative IOLs. This would also allow detection of any late complications or adverse events. Studies are required that include functionally relevant outcome measures such as unaided reading speed, spectacle dependence and measures of dysphotopsia, to compare accommodative IOLs to multifocal IOLs and monovision strategies for the correction of pseudophakic presbyopia.

A standard framework of outcome measures would facilitate future analyses of combined data.

Future trials should follow CONSORT guidelines (CONSORT 2012) to ensure that reporting of randomised controlled trials is complete. Variable increase in accommodative function observed in people who received accommodative IOLs suggests the need for improvements in IOL design. Trials comparing accommodative IOLs other than the HumanOptics 1CU with monofocal and multifocal controls are required, to determine the best performing IOL for use in cataract surgery and refractive lens exchange.

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