Different-sized incisions for phacoemulsification in age-related cataract (Review)

Methodological quality of the review: High confidence

Author: Jin C, Chen X, Law A, Kang Y, Wang X, Xu W, Yao K.

Region: Turkey, Spain, Switzerland, France, China, South Korea, Korea, Italy, Bosnia and Herzegovina, India.

Sector: Cataract surgery

Sub-sector: Incision

Type of cataract: Age-related cataract

Equity focus: None specified

Quantitative synthesis method: None specified

Qualitative synthesis method: Not applicable

Background:

Age-related cataract is the principal cause of blindness and visual impairment in the world. Phacoemulsification is the main surgical procedure used to treat cataract. The comparative effectiveness and safety of different-sized incisions for phacoemulsification has not been determined.

Research objectives:

The aim of this systematic review was to assess the effectiveness and safety of smaller versus larger incisions for phacoemulsification in age-related cataract. The primary outcome of this review was surgically induced astigmatism at three months after surgery.

Main findings:

Authors included a total of 26 randomized controlled trials (RCTs), conducted in Bosnia and Herzegovina, China, France, India, Italy, Korea, Spain, Switzerland, and Turkey. Half of the 26 trials were conducted in China. Most studies were attributed to unclear or low risk of bias. The included RCTs compared four different-sized incisions: <= 1.5mm, 1.8mm, 2.2mm, and approximately 3.0 mm. These incisions were performed using three different techniques: coaxial and biaxial microincision phacoemulsification (CMICS and B-MICS) and standard phacoemulsification. Not all studies provided data in a form that could be included in this review. Five studies had three arms.

Out of the 26 studies, 15 compared C-MICS (2.2 mm) with standard phacoemulsification (about 3.0 mm). Very low-certainty evidence suggested less surgically induced astigmatism in the C-MICS group at three months compared with standard phacoemulsification. Authors report that there was low-certainty evidence of little or no difference in endothelial cell loss and central corneal thickness comparing C-MICS with standard phacoemulsification (mean difference (MD) -0.19 diopters (D), 95% confidence interval (CI) -0.30 to -0.09; 996 eyes; 8 RCTs).

Nine included trials compared C-MICS (1.8 mm) with standard phacoemulsification (about 3.0 mm). Authors note that very low-certainty evidence suggest less astigmatism at three months in the C-MICS group compared with standard phacoemulsification group (MD -0.23 D, 95% CI -0.34 to -0.13; 561 eyes; 5 RCTs). Six studies compared C-MICS (1.8 mm) with C-MICS (2.2 mm). In addition, authors stated that there was low-certainty evidence that astigmatism, visual acuity, and central corneal thickness were similar in the two groups at three months (MD 0.04 D, 95% CI -0.09 to 0.16; 259 eyes; 3 RCTs), (MD 0.01 logMAR, 95% CI -0.01 to 0.04; 200 eyes; 3 RCTs), and (MD 0.45 μm, 95% CI -2.70 to 3.60; 100 eyes; 1 RCT).

Four studies compared B-MICS (<= 1.5 mm) with standard phacoemulsification (about 3.0 mm). Astigmatism was similar in the two groups at three months (MD -0.01 D, 95%CI -0.03 to 0.01; 368 eyes; 2 RCTs; moderate-certainty evidence). Authors reported low-certainty evidence on visual acuity, suggesting little or no difference between the two groups (MD -0.02 logMAR, 95% CI -0.04 to -0.00; 464 eyes; 3 RCTs). Low-certainty evidence on endothelial cell loss and central corneal thickness also suggested little or no difference between the two groups (MD 55.83 cells/mm2, 95% CI -34.93 to 146.59; 280 eyes; 1 RCT) and (MD 0.10 μm, 95% CI -14.04 to 14.24; 90 eyes; 1 RCT).

Authors found that none of the trials reported on quality of life. One trial reported that no participants experienced endophthalmitis or posterior capsule rupture; they also reported little or no difference between incision groups regarding corneal edema (risk ratio 1.02, 95% CI 0.40 to 2.63; 362 eyes).

Based on findings from this review, authors concluded that phacoemulsification with smaller incisions was not consistently associated with less surgically induced astigmatism compared with phacoemulsification with larger incisions. Reviewers note that coaxial microincision phacoemulsification may be associated with less astigmatism than standard phacoemulsification, but the difference was small, in the order of 0.2 D, and the evidence was uncertain. Authors state that safety outcomes and quality of life were not adequately reported; these should be addressed in future studies.

Methodology:

Authors included randomized controlled trials (RCTs) comparing different-sized incisions in people with age-related cataract undergoing phacoemulsification.

Authors searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE Ovid, Embase Ovid, PubMed, LILACS (Latin American and Caribbean Health Sciences Literature Database), the metaRegister of Controlled Trials, ClinicalTrials.gov, and the WHO International Clinical Trials Registry Platform (ICTRP). Review authors did not use any date or language restrictions in the electronic searches for trials.

Two review authors independently screened studies for inclusion, extracted data and assessed the methodological quality of included studies. Discrepancies were resolved by discussion to reach consensus.

For continuous outcomes, authors measured the treatment effect as mean difference with 95% confidence intervals. For dichotomous outcomes, treatment effect was measured using risk ratio. Authors assessed heterogeneity of included studies using I2 statistic. Authors note, that as fewer than 10 studies were included in the review, publication bias was not assessed using funnel plots. Data syntheses consisted of a meta-analyses, fixed-effect model was used for meta-analysis of three or fewer trials; and a random-effects model was used to include more than three trials.

Applicability/external validity:

Authors note that the low- to very low-certainty evidence did not consistently show that phacoemulsification with smaller incisions was associated with less surgically induced astigmatism compared with phacoemulsification with larger incisions. Poor reporting of the methods of all included studies resulted in a judgement of mostly unclear risk of bias.

Geographic focus:

Half of the included studies were conducted in China and authors note that the meta-analysis was possible for the primary review outcome comparing all four different-sized incisions. However, authors report that results were inconsistent when comparing all four incisions, and study methods were poorly reported.

Quality assessment:

High confidence was attributed in the conclusions about the effects of this study. Authors used appropriate methods to search for eligible studies, avoiding publication bias. Rigorous methods were also used to screen studies for inclusion, extract data and assess methodological quality of included studies. Methods used to synthesize the data were clearly reported.