Visual acuity improvements after implantation of toric intraocular lenses in cataract patients with astigmatism: a systematic review

Methodological quality of the review: Low confidence

Author: Agresta B, Knorz MC, Donatti C, Jackson D.

Region: Not specified

Sector: Visual acuity

Sub-sector: Intraocular lenses, cataract, astigmatism

Equity focus: None Specified

Review Type: Effectiveness Review

Quantitative synthesis method: Narrative analysis

Qualitative synthesis methods: Not applicable

Background

Worldwide, cataracts appear to be the common and significant cause of visual impairment. In the UK, cataract surgery happens to be one of the most commonly performed surgery, in that 10% of people aged 65 years and over have received cataract surgery. Despite this, 30% of this population have visually impaired cataract. During cataract surgery, astigmatism can be corrected by prescription glasses, contact lenses, corneal relaxing incisions astigmatic keratotomies, limbal relaxing incisions. However, astigmatism and cataracts reduce the quality of life of patients.

Research objectives

To evaluate uncorrected distance visual acuity (UDVA) as an outcome in treating astigmatic cataract patients, to assist clinicians or ophthalmologists in their decision-making process regarding available interventions.

Main findings

Eleven studies were identified that measured uncorrected visual acuity. Although uncorrected near visual acuity (UNVA) and uncorrected intermediate visual acuity (UIVA) were part of the inclusion criteria, no studies were found that report on them. The 11 studies that reported UDVA were made up of 7 observational studies, 1 prospective cohort study and 1 retrospective observational. The study used Oxford Centre for Evidence-based Medicine grades of evidence to classified nine studies as IIIb and two as Ib.

The review found gains in improvement for UDVA. Across all the 11 included studies, the post-operative UDVA values were closer to a normal sight score (20/20 Snellen) in four models of toric IOLs. The greatest increase in VA had a human Optic Microsil with an increase of 0.92 LogMAR in UDVA while the smallest improvement in VA indicated that VA increased by only 0.23 LogMAR.

The review provided evidence to suggest that toric IOLs increase the uncorrected distance visual acuity in cataract patients. Uncorrected visual acuity is, however, one of the many possible outcomes to measure the efficacy of toric IOLs.

Methodology

The authors conducted a search on several databases including Medline, Medline In-progress (from 1948 till when the review was ended), Embase (1988 to 2011) and Evidence-based Review were accessed via OVID platform. The search used terms such as lens diseases, cataract, aphakia, cataract extraction, toric, lens implantation, lens. Only studies written in English were included in the review.

The identified study was graded using the Oxford Centre for Evidence-Based Medicine Grades of Evidence. The analysis focused on UDVA, UIVA and UNVA

Details were not reported with regards to the methods used to analyze the included studies.

Applicability/external validity

The review authors did not discuss the applicability/external validity of the results.

Geographic focus

The geographic focus of studies included in the review were not provided.

Quality assessment

Overall, there is low confidence in the conclusions about the effects of this study. Although this review is based on comprehensive searches of literature from different databases, language bias was not avoided and authors of included studies were not contacted for further potentially relevant studies. The review authors reported the type of included studies, interventions and possible outcomes, although the type of participants/settings/population was not clear. It is not clear if selection bias was avoided by the authors, as they did not report if selection of studies for inclusion were conducted by two reviewers independently. Additionally, they did not report assessing the quality and risk of bias of included studies, impacting on the reliability of the review.