Methodological quality of the review: High confidence

Author: Calladine D, Evans JR, Shah S, Leyland M.

Region: Europe, Saudi Arabia, United States of America (USA), India and China.

Sector: Intraocular lenses, cataract extraction

Sub-sector: Multifocal Intraocular lens (IOL), monofocal IOL.

Type of cataract: Age-related cataract

Equity focus: None specified

Review type: Effectiveness review

Quantitative synthesis method: Meta-analysis

Qualitative synthesis methods: Not applicable

Background

Good unaided distance visual acuity is now a realistic expectation following cataract surgery and intraocular lens (IOL) implantation. Near vision, however, still requires additional refractive power, usually in the form of reading glasses. Multiple optic (multifocal) IOLs are available which claim to allow good vision at a range of distances. It is unclear whether this benefit outweighs the optical compromises inherent in multifocal IOLs.

Research objectives

To assess the effects of multifocal IOLs including effects on visual acuity, subjective visual satisfaction, spectacle dependence, glare and contrast sensitivity, compared to standard monofocal lenses in people undergoing cataract surgery.

Main findings

Authors included 16 parallel group randomized trials were included in which any type of diffractive or refractive multifocal intraocular lens was compared with monofocal intraocular lens implantation. Three were multicentre and 13 were single-centre studies. Included studies were conducted in Europe, Saudi Arabia, USA, India and China.

Authors found that similar distance acuity is achieved with both types of lenses implanted (pooled risk ratio (RR) for unaided visual acuity worse than 6/6: 0.98, 95% confidence interval (CI) 0.91 to 1.05). Evidence also indicated that people with multifocal lenses had better near vision but due to methodological and statistical heterogeneity between the studies, the authors did not calculate a pooled estimate for effect on near vision. They concluded that multifocal IOLs were effective at improving near vision relative to monofocal IOLs. Whether that improvement outweighs the adverse effects of multifocal IOLs will vary between patients. Motivation to achieve spectacle independence was likely to be the deciding factor.

Review authors reported the need for a core set of validated outcome measures in trials comparing multifocal and monofocal lenses.

Methodology

Selection criteria consisted of randomized controlled trials comparing a multifocal IOL of any type with a monofocal IOL as control. Both unilateral and bilateral implantation trials were included. Trials included participants who were undergoing cataract surgery and intraocular lens implantation in one or both eyes. Primary outcome measures included were (1) Distance visual acuity, and (2) Near visual acuity and spectacle dependence. Secondary outcomes included depth of field, contrast sensitivity, glare, validated instruments assessing quality of life and informal (non-validated) subjective assessment of visual function.

Authors conducted a search on several databases including CENTRAL (2012), EMBASE (1980-2012) and MEDLINE (1946-2012) and did not use any date or language restrictions. Reference lists of relevant studies and Martin Leyland’s personal database of trials were also searched. For the first version of this review, authors contacted investigators of included trials and manufacturers of multifocal intraocular lenses for additional published and unpublished trials; for this updated version authors did not conduct the same procedure.  Two authors independently examined the title and abstracts from electronic searches, extracted data, and assessed risk of bias of included studies.

Authors pooled data using a random effects model where three of more studies contributed to the analysis, otherwise the authors tabulated data when data synthesis was not possible. They assessed heterogeneity and reporting biases of included studies, but did not conduct a sensitivity analysis.

Applicability/external validity

Authors discussed overall completeness and applicability of evidence. Authors graded the quality of evidence as moderate and there was substantial methodological and statistical heterogeneity especially for measurement of best-corrected distance visual acuity, both unaided and best corrected near visual acuity and patient reported spectacle dependence, making generalizations from the data more difficult.

Geographic focus

Included studies were largely from high-income settings such as Europe and the USA, only one study was included from a low- and middle-income country (India).  Nevertheless, authors did not describe the applicability of the results to low- and middle-income countries.

Quality assessment

This review used clear and transparent methods of search, inclusion and methods of analysis, avoiding language, publication and selection bias. Authors used appropriate criteria to assess the quality and risk of bias in analysing included studies.  Limitations were acknowledged by the authors and no other quality issues were identified. Therefore, high confidence in the conclusions about the effects was attributed to this study.