Comparing two different techniques of removing cataracts

Cataract is a clouding of the lens in the eye, which most commonly occurs due to increasing age. This can only be treated with an operation, and the aim of this review was to assess two different surgical methods. The first, called manual small incision cataract surgery (MSICS) involves using instruments to remove the lens from the eye through a small incision. The second, phacoemulsification, involves using a high frequency ultrasound probe to fragment the lens, and this machine also removes the lens fragments from the eye.

We searched the literature in July 2013 and identified eight randomised controlled trials that compared these two techniques. These included a total of 1708 participants randomly allocated to MSICS or phacoemulsification. The studies were carried out in India, Nepal and South Africa.

Not all studies reported the outcomes of visual acuity that we aimed to assess, making it difficult to draw definite conclusions. Better uncorrected visual acuity was seen in the short term with phacoemulsification; however, there were no differences in best-corrected visual acuity (i.e. after correction with spectacles). There appeared to be no significant difference regarding uncorrected visual acuity between the two techniques at six months in the one trial that reported at that time point. There was a lack of long-term data (one year or more after surgery). Very few participants were reported to have poor visual outcomes or complications (such as posterior capsule rupture) from the surgery. The cost of phacoemulsification was documented in one study only, and this was more than four times the cost of MSICS.

In this setting, the two techniques appear to be comparable in terms of visual acuity outcomes and complications. However further studies with a longer follow-up period are needed to better assess these outcomes.

Authors' conclusions: 

On the basis of this review, removing cataract by phacoemulsification may result in better UCVA in the short term (up to three months after surgery) compared to MSICS, but similar BCVA. There is a lack of data on long-term visual outcome. The review is currently underpowered to detect differences for rarer outcomes, including poor visual outcome. In view of the lower cost of MSICS, this may be a favourable technique in the patient populations examined in these studies, where high volume surgery is a priority. Further studies are required with longer-term follow-up to better assess visual outcomes and complications which may develop over time such as posterior capsule opacification.

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Background: 

Age-related cataract is a major cause of blindness and visual morbidity worldwide. It is therefore important to establish the optimal technique of lens removal in cataract surgery.

Objectives: 

To compare manual small incision cataract surgery (MSICS) and phacoemulsification techniques.

Search strategy: 

We searched CENTRAL (which contains the Cochrane Eyes and Vision Group Trials Register) (The Cochrane Library 2013, Issue 6), Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE (January 1946 to July 2013), EMBASE (January 1980 to July 2013), Latin American and Caribbean Literature on Health Sciences (LILACS) (January 1982 to July 2013), Web of Science Conference Proceedings Citation Index - Science (CPCI-S) (January 1970 to July 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 23 July 2013.

Selection criteria: 

We included randomised controlled trials (RCTs) for age-related cataract that compared MSICS and phacoemulsification.

Data collection and analysis: 

Two authors independently assessed all studies. We defined two primary outcomes: 'good functional vision' (presenting visual acuity of 6/12 or better) and 'poor visual outcome' (best corrected visual acuity of less than 6/60). We collected data on these outcomes at three and 12 months after surgery. Complications such as posterior capsule rupture rates and other intra- and postoperative complications were also assessed. In addition, we examined cost effectiveness of the two techniques. Where appropriate, we pooled data using a random-effects model.

Main results: 

We included eight trials in this review with a total of 1708 participants. Trials were conducted in India, Nepal and South Africa. Follow-up ranged from one day to six months, but most trials reported at six to eight weeks after surgery. Overall the trials were judged to be at risk of bias due to unclear reporting of masking and follow-up. No studies reported presenting visual acuity so data were collected on both best-corrected (BCVA) and uncorrected (UCVA) visual acuity. Most studies reported visual acuity of 6/18 or better (rather than 6/12 or better) so this was used as an indicator of good functional vision. Seven studies (1223 participants) reported BCVA of 6/18 or better at six to eight weeks (pooled risk ratio (RR) 0.99 95% confidence interval (CI) 0.98 to 1.01) indicating no difference between the MSICS and phacoemulsification groups. Three studies (767 participants) reported UCVA of 6/18 or better at six to eight weeks, with a pooled RR indicating a more favourable outcome with phacoemulsification (0.90, 95% CI 0.84 to 0.96). One trial (96 participants) reported UCVA at six months with a RR of 1.07 (95% CI 0.91 to 1.26).

Regarding BCVA of less than 6/60: there were only 11/1223 events reported. The pooled Peto odds ratio was 2.48 indicating a more favourable outcome using phacoemulsification but with wide confidence intervals (0.74 to 8.28) which means that we are uncertain as to the true effect.

The number of complications reported were also low for both techniques. Again this means the review is underpowered to detect a difference between the two techniques with respect to these complications. One study reported on cost which was more than four times higher using phacoemulsification than MSICS.

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