Summary of findings
1 Risk in phacoemulsification group ranged from 0 per 1000 to 25 per 1000 in the included studies; the median risk was 0. We have therefore estimated a low risk in the phacoemulsification group at 1 per 1000.
2 Downgraded for risk of bias: several items on risk of bias assessment not clearly reported.
3 Downgraded for imprecision: wide confidence intervals.
4 Downgraded for indirectness (not measured at 12 months).
5 Downgraded for inconsistency: only one study reported so not possible to assess.
Description of the condition
Cataract is the opacification of the normally transparent lens of the eye and occurs as a result of denaturation of lens proteins. This cloudiness can cause a decrease in vision and may lead to eventual blindness. Most cataracts are age-related. The density and location of the cataract determines the amount of vision affected. Initially, cataracts may not affect vision and if the cataract remains small or at the periphery of the lens, the visual changes may be minor. If the cataract forms in the area of the lens directly behind the pupil, vision may be significantly impaired. It is not thought to be reversible and surgery is currently the only treatment option. In the months or years after cataract surgery a small percentage of people will develop a condition called posterior capsular thickening which can be treated. A laser treatment, YAG laser capsulotomy, makes a small opening in the back of the lens capsule, which restores vision.
The World Health Organization (WHO) estimated from a recent global review of surveys that there are 37 million people worldwide who were blind in 2002 (Passolini 2004; Resnikoff 2004) and that age-related cataract remained the leading cause of blindness globally in 2002, as it was in 1990. Fifty per cent of total world blindness is thought to be due to cataract, with the majority of blinding cataract found in developing countries. The contribution of cataracts to blindness globally is likely to grow due to an ageing population and unsuccessful attempts to control this blinding condition in low- and middle-income countries (WHO 2005).
Description of the intervention
Phacoemulsification was first described in 1967 by Charles D. Kelman, an American ophthalmologist (1930 to 2004). It is the most commonly performed method of cataract extraction in the developed world and involves ultrasonic fragmentation of the crystalline lens. The incision is small (with a standard size of around 2.75 mm, but may range from 2.2 mm to 3.2 mm) which allows rapid visual rehabilitation postoperatively and low induced astigmatism. This technique requires a phacoemulsification machine which may cost GBP 20,000 to GBP 45,000 and has high disposable and maintenance costs. Phacoemulsification requires extensive surgical training, particularly the necessity to carry out a continuous capsulorhexis.
Manual small incision cataract surgery (MSICS) was first described by Blumenthal 1992. In Asia and Africa there has been a renewal of interest in this technique (Ruit 2000) as an alternative to phacoemulsification, because it is considerably less costly but has similar benefits of rapid visual recovery and reduced astigmatism (Yorston 2005). It involves a 6 mm to 6.5 mm scleral incision, just large enough to allow insertion of a 6 mm intraocular lens (IOL). There are various different techniques described for performing the capsulotomy in MSICS, for example, the can-opener method (Gogate 2005b), the continuous curvilinear capsulorhexis (Gogate 2003) and the endocapsular technique where the incision is from pupil margin to pupil margin. The lens is delivered into the anterior chamber, hydroextracted and aspirated. The posterior capsule of the lens is left intact. This technique is technically more difficult than a standard manual extracapsular extraction (ECCE).
Figure 1 summarises the different types of cataract surgery.
|Figure 1. Types of cataract surgery|
How the intervention might work
Cataract surgery consists of removing the lens of the eye and replacing it with an artificial lens called an intraocular lens. IOLs can be made from a range of materials, and can be of varying size, shape and refracting power. Before cataract surgery the eye to be operated on is measured so that an IOL of the correct power (strength) can be inserted after the cataract has been removed. The IOL is usually placed inside the 'bag' of the lens capsule inside the eye. Other options for lens replacement include contact lenses and cataract glasses.
Why it is important to do this review
Although phacoemulsification is the most technologically advanced method providing small-incision, sutureless surgery it requires considerable resources in the form of the initial capital outlay for the phacoemulsification machine, and there are considerable ongoing costs due to consumables, maintenance and training of surgeons. It is the procedure of choice for cataract surgery in high-income countries.
From a global perspective phacoemulsification is too costly for many developing countries where there is the highest incidence of cataract blindness. Manual small incision cataract surgery and ECCE are alternative techniques available at a lower cost. A key question is whether the resources required for phacoemulsification are justified in a lower-income setting.
This review in its original form ‘Surgical interventions for age-related cataract’ (Riaz 2006) compared the outcomes of different cataract surgical techniques. The techniques included initially were intracapsular extraction (ICCE), ECCE and phacoemulsification. In 2006 it was revised and a fourth surgical technique, MSICS, was added to the review.
Following consultation with the authors and the Cochrane Eyes and Vision Group this update has been divided into three smaller reviews each using the same outcome measures but only comparing two surgical methods within each review. The ICCE technique is no longer included as this method is no longer used as a primary procedure.
The cataract surgical techniques compared in these three reviews are:
The aim of this review is to compare the effects of two types of cataract surgery: manual small incision cataract surgery (MSICS) and phacoemulsification.
Our secondary objective is to compare the costs of the two procedures as reported in included trials.
Criteria for considering studies for this review
Types of studies
We include randomised controlled trials (RCTs) only in this review.
Types of participants
We include trials where participants were people with age-related cataract.
Types of interventions
We include trials that compared MSICS with phacoemulsification, followed by implantation of a posterior chamber intraocular lens (IOL) in both techniques.
Types of outcome measures
Postoperative visual acuity
- proportion of people achieving good functional vision, defined as presenting* visual acuity better than or equal to 6/12 in the operated eye.
- proportion of people with a poor outcome after surgery, defined as best-corrected visual acuity (BCVA) worse than 6/60 in the operated eye.
* 'Presenting visual acuity' is vision that the person uses in normal life, i.e. with or without glasses, if worn.
- Intraoperative complications
- capsular rupture with or without vitreous loss
- iris prolapse
- postoperative inflammation
- other complications as reported
- Long-term complications (one year or more after surgery)
- posterior capsule opacification
- retinal detachment
- cystoid macular oedema
- corneal endothelial cell loss
- corneal decompensation
- other complications as recorded
- Quality of life (self care, mobility, social and mental function) as reported
- Cost effectiveness
Outcomes were measured at three months and one year after surgery. As studies may not report outcomes exactly at these time points, data collection was considered within the following time periods:
- three months: from four weeks to less than six months
- 12 months: from six months to less than 18 months
Search methods for identification of studies
We searched the Cochrane Central Register of Controlled Trials (CENTRAL) 2013, Issue 6, part of The Cochrane Library. www.thecochranelibrary.com (accessed 23 July 2013), 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 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.
See: Appendices for details of search strategies for CENTRAL (Appendix 1), MEDLINE (Appendix 2), EMBASE (Appendix 3), LILACS (Appendix 4), CPCI-S (Appendix 5), mRCT (Appendix 6), ClinicalTrials.gov (Appendix 7) and the ICTRP (Appendix 8).
Searching other resources
We searched the reference lists of identified included studies. We contacted study authors and other experts in the field to identify unpublished studies or studies sent for publication or in press.
Data collection and analysis
Selection of studies
Two review authors independently screened the titles and abstracts resulting from the electronic searches. Duplicate records were removed, as were obviously irrelevant titles and abstracts. We obtained full-text copies of any report referring to definitely or possibly relevant trials. Multiple reports of the same study were linked together. We assessed these full-text reports for compliance of studies with eligibility criteria, and then assessed trials that met these criteria for methodological quality.
All studies that were excluded at this stage were documented and reasons for exclusion provided.
Data extraction and management
We extracted data using a form developed by the Cochrane Eyes and Vision Group. Two authors extracted data and compared the results for differences. We resolved discrepancies by discussion. Any disagreements which could not be resolved were initially addressed by contacting the study authors, and if this was unsuccessful were reported in the review. Data were entered onto a spreadsheet, checked for accuracy by all review authors, and then cut and pasted into Review Manager 5 (RevMan 2012).
Assessment of risk of bias in included studies
We assessed the risk of bias in each study using The Cochrane Collaboration's tool for assessing the risk of bias as detailed in Chapter 8 of the Cochrane Handbook for Systematic Reviews of interventions (Higgins 2011). We considered the following parameters: sequence generation, allocation sequence concealment, masking (blinding), incomplete outcome data, selective outcome reporting and other potential sources of bias. We judged whether they were at high risk of bias, low risk of bias or unclear. Two review authors independently assessed the risk of bias and disagreement was resolved by discussion. Authors were not masked to the report authors and trial results during the assessment.
Measures of treatment effect
The outcomes for this review were largely dichotomous (i.e. postoperative visual acuity and complications). Our measure of treatment effect was the risk ratio. For outcomes that occurred rarely (in less than 10% of the cohort), we used the Peto odds ratio. Corneal endothelial cell loss was reported as a continuous variable and was analysed using the mean difference. Currently the review does not include data on quality of life. In future updates this may become available. It may be reported as a continuous variable, in which case the mean difference will be used.
Unit of analysis issues
In all studies included in this review, data were reported for one eye per person, although it was not always clear how the study eye was selected.
Dealing with missing data
We collected information on follow-up by treatment groups, and the reasons for missing data, although this was not always reported. The analyses in this review are based on available data and therefore assume that missing data are missing at random. We originally planned to investigate how reasonable this assumption is by doing a series of sensitivity analyses with different assumptions about the missing data using methods as set out by White 2008. However, data currently included in the review are sparse and we have therefore not done these sensitivity analyses for this initial version of the review.
Assessment of heterogeneity
We assessed heterogeneity in several ways. Firstly, by documenting clinical and methodological differences between the studies. Secondly by examining the forest plots to see whether the estimates of effect are consistent, and thirdly by considering the I² value and Chi² test for heterogeneity (bearing in mind that the Chi² test has low power when the number of trials is small) (Higgins 2003).
Assessment of reporting biases
The main reporting biases that we planned to consider were publication bias and outcome reporting bias. Currently there are not enough trials included in the review to assess publication bias. In order to assess the possibility of outcome reporting bias we did a review outcome matrix using the ORBIT classification (Kirkham 2010).
Where data were available, we pooled the results using a random-effects model if there were more than three studies, and a fixed-effect model if there were three or fewer studies. For data on complications, as the number of events was small, we used the Peto odds ratio (fixed-effect model). As a general rule, if there was substantial heterogeneity as defined above (Assessment of heterogeneity), we planned not to report a pooled estimate, depending on the size of studies and consistency of the effect estimates.
Subgroup analysis and investigation of heterogeneity
We did not plan or conduct any subgroup analyses.
We planned to do a sensitivity analysis excluding trials at high risk of bias and investigating the impact of missing data (see Dealing with missing data). However, currently there are not enough data to enable this.
Summary of findings table
We prepared a 'Summary of findings' table and assessed the quality of the body of evidence for each outcome using the GRADE approach as described in Chapter 12 of the Cochrane Handbook for Systematic Reviews of interventions (Schünemann 2011). This was done by one author (JE) and checked by the other authors.
Description of studies
Results of the search
The electronic searches yielded a total of 748 records (Figure 2). After deduplication we screened the title and abstract of 541 records. We excluded 523 records as not relevant to the scope of the review. We obtained full-text copies of 17 records for further investigation. We excluded eight studies, see Characteristics of excluded studies and included eight studies (nine reports) see Characteristics of included studies.
|Figure 2. Results from searching for studies for inclusion in the review.|
We included eight randomised controlled trials (RCTs) for analysis in this review (Cook 2012; George 2005; Ghosh 2010; Gogate 2005a; Gogate 2010; Ruit 2007; Singh 2009; Venkatesh 2010). See Characteristics of included studies for further details. All studies compared manual small incision cataract surgery (MSICS) with phacoemulsification. One trial had an additional extracapsular extraction (ECCE) arm (George 2005).
Participants: A total of 1708 people were included in these studies: 200 (Cook 2012); 124 (George 2005); 224 (Ghosh 2010); 400 (Gogate 2005a); 200 (Gogate 2010); 108 (Ruit 2007); 182 (Singh 2009); 270 (Venkatesh 2010).
Demographics: The average age of participants ranged from 56 to 68. Approximately equal numbers of women and men were enrolled (range percentage of women from 44.2% to 61%).
Location: Five of the included studies were conducted in India (George 2005; Ghosh 2010; Gogate 2005a; Gogate 2010; Venkatesh 2010), two in Nepal (Ruit 2007; Singh 2009) and one in South Africa (Cook 2012).
Outcomes: All eight studies evaluated Snellen visual acuity outcomes. Six studies reported visual acuity as their main outcome whereas George 2005 reported endothelial cell loss and surgery-induced astigmatism as their main outcome, and Ghosh 2010 reported macular thickness as the primary outcome. Postoperative complications were recorded in all studies.
Follow-up: Singh 2009 reported results on the first postoperative day only; George 2005; Gogate 2005a; Gogate 2010 and Venkatesh 2010 reported results at six weeks, Cook 2012 reported results at eight weeks; Ghosh 2010 and Ruit 2007 reported data up to six months postoperatively.
See Characteristics of excluded studies table.
Risk of bias in included studies
|Figure 3. Risk of bias graph: review authors' judgements about each risk of bias item presented as percentages across all included studies.|
|Figure 4. Risk of bias summary: review authors' judgements about each risk of bias item for each included study.|
All eight trials clearly stated how participants were allocated to each arm of the study. Five trials described using picking a ball or ‘ballots’ for assignment of treatment and surgeon (Cook 2012; Ghosh 2010; Gogate 2005a; Gogate 2010; Ruit 2007). Two studies used computer-generated random numbers (George 2005; Venkatesh 2010) and another study used a random number table (Singh 2009). Allocation concealment was described in five studies (Cook 2012; Ghosh 2010; Gogate 2005a; Gogate 2010; Venkatesh 2010).
Four studies reported that masking was carried out and that postoperative assessors were masked to the nature of surgery (Cook 2012; Ruit 2007; Singh 2009; Venkatesh 2010). However, obvious differences in postoperative appearance of the eye in each group may influence the ability to mask assessors.
Incomplete outcome data
Follow-up rates were variable between the included studies: 82.5% (Cook 2012); 91% (George 2005); 86% (Ghosh 2010); 93% (Gogate 2005a); 73% (Gogate 2010); 87% (Ruit 2007);100% (Singh 2009); 85% (Venkatesh 2010) respectively. Only Cook 2012 stated the reason for attrition, which was the distance needed to travel by participants living in rural areas.
The only intraoperative complication described in George 2005 was posterior capsular rupture. Otherwise, a range of outcomes were reported in all other studies. Without access to the protocols for the studies it was difficult to assess this bias formally. However, we compiled an 'outcome reporting matrix' ( Table 1) using the ORBIT classification (Kirkham 2010). We did not identify any cause for concern.
Other potential sources of bias
The level of surgical experience for each technique performed may be a source of bias. However, this would only be the case if there were imbalance between study groups in level of experience of the surgeon. In Cook 2012, 35% of phacoemulsification surgeries and 58% of MSICS surgeries were done by a team of five consultants. The remainder of surgery was done by 10 registrars, who were reported to be competent in the technique but had varying levels of experience. If the assumption is made that consultants were more experienced, this may be a potential source of bias in favour of MSICS outcomes.
In George 2005; Gogate 2005a; Ruit 2007 and Venkatesh 2010, all surgeons had comparable levels of experience. In Singh 2009 there was only one surgeon and it is not stated whether he had equal surgical experience of both techniques. In Ghosh 2010 there were two surgeons who performed equal amounts of surgery. In Gogate 2010 neither the number of surgeons nor the level of surgical experience is stated.
Effects of interventions
Good functional vision
We defined 'good functional vision' as presenting visual acuity of 6/12 or better. No studies reported presenting visual acuity so we report both uncorrected (UCVA) and best-corrected visual acuity (BCVA). Most studies reported outcomes of 6/18 or better, rather than 6/12 or better, so this outcome has been used as an indicator of good functional vision.
Uncorrected visual acuity (UCVA)
Five studies reported UCVA of 6/18 or better, with one study reporting this outcome at one day only (Singh 2009), two studies at six weeks (Gogate 2005a; Venkatesh 2010), one study at eight weeks (Cook 2012) and one study at six months (Ruit 2007).
At one day postoperatively, UCVA of 6/18 or better was found in 77.7% of participants in the MSCIS group and 68% of participants in the phacoemulsification group (P = 0.0655) (Singh 2009).
At six weeks, Gogate 2005a reported UCVA of 6/18 or better in 133/187 (71%) of MSICS participants compared to 150/185 (81%) of phacoemulsification participants (risk ratio (RR) 0.88, 95% confidence interval (CI) 0.78 to 0.98). Venkatesh 2010 reported this outcome in 96/117 (82%) MSICS participants and 99/113 (88%) phacoemulsification participants (RR 0.94, 95% CI 0.84 to 1.04). At eight weeks, Cook 2012 reported this outcome in 63/85 (74%) MSICS participants and 69/80 (86%) phacoemulsification participants (RR 0.86, 95% CI 0.74 to 1.00). The pooled RR for this outcome was 0.90, (95% CI 0.84 to 0.96) which favours phacoemulsification ( Analysis 1.1).
Best-corrected visual acuity (BCVA)
More studies reported BCVA ( Analysis 1.3). At three months there was no difference between MSICS and phacoemulsification groups (pooled RR 0.99, 95% CI 0.98 to 1.01) ( Analysis 1.3). One trial only reported at six months (Ruit 2007) with a RR of 1.0 (95% CI 0.94 to 1.06) ( Analysis 1.4).
Poor visual outcome after surgery
We defined a poor outcome after surgery as BCVA of less than 6/60.
Six studies reported poor visual outcome data within three months postoperatively, with no cases in either group in three out of six studies. In total 8/617 MSICS cases and 3/606 phacoemulsification cases had BCVA worse than 6/60. With low numbers of events, the true estimate of effect is uncertain with a pooled Peto OR of 2.48 in favour of phacoemulsification and wide confidence intervals (95% CI 0.74 to 8.28; Analysis 1.5).
Intraoperative surgical complications
Posterior capsule rupture (PCR) was reported in all studies ( Analysis 1.7). In most studies few cases of PCR were reported. The number of cases reported varied between studies from no events in either group (George 2005) to 10/100 in the MSICS and 4/100 in the phacoemulsification group (Cook 2012). Overall there was little evidence of any difference between the two intervention groups (Peto OR 1.07, 95% CI 0.63 to 1.83).
Five studies reported iridodialysis ( Analysis 1.8). There were too few cases (seven) to detect any difference between MSICS and phacoemulsification (Peto OR 2.37, 95% CI 0.54 to 10.45). Two studies reported zonule dialysis (Gogate 2005a; Singh 2009) but again the number of cases (three) was low.
Three studies (Gogate 2005a; Gogate 2010; Ruit 2007) reported extension of capsulorrhexis during surgery ( Analysis 1.9). This appeared to occur more commonly in the phacoemulsification group, but again the number of cases was low (six); Peto OR 0.26 (95% CI 0.05 to 1.30).
In Gogate 2005a, 2/199 cases allocated to the phacoemulsification groups were converted to MSICS; in Gogate 2010 this was 5/100 cases (three due to zonular dialysis and two due to posterior capsule tears), in Cook 2012 8/100 cases (due to hard nucleus) and in Venkatesh 2010 3/137 cases.
Early postoperative corneal oedema (occurring at day 1 to day 7) was reported in six studies ( Analysis 1.11) with a total of 60/739 cases in the MSICS group and 93/737 cases in the phacoemulsification group. Overall there appeared to be more cases of early postoperative corneal oedema in the phacoemulsification group (Peto OR 0.58, 95% (CI) 0.41 to 0.83). In four studies, no events of corneal oedema were reported at three to six weeks ( Analysis 1.12).
Posterior capsule opacification was reported in two studies ( Analysis 1.13). At six weeks no cases were observed in Gogate 2005a, and at six months 20/46 MSICS versus 7/48 phacoemulsification cases were observed in Ruit 2007 (RR 2.98, 95% CI 1.39 to 6.37).
No significant difference between percentage endothelial cell loss was found between the two techniques ( Analysis 1.14). George 2005 reported a 5.41% endothelial cell loss at six weeks in the phacoemulsification group, and 4.21% in the MSICS group (P = 0.855). Gogate 2010 reported a mean endothelial cell loss at one week of 16.1% in the phacoemulsification group, and 12.2% in the MSICS group (P = 0.06). At six weeks the percentage loss was 18.4% in the phacoemulsification group, and 17.7% in the MSICS group (P = 0.44).
Other reported findings
Surgically induced astigmatism (SIA)
At one day postoperatively, Singh 2009 reported a mean induced astigmatism of 0.11 dioptre (D) (SD 0.74) for the phacoemulsification group and 0.09 (SD 0.82) for the MSICs group.
At six to eight weeks postoperatively, three studies reported a greater SIA in the MSICS groups: George 2005 (mean SIA 1.1 ± 0.95 D MSICS versus 0.77 ± 0.65 D phacoemulsification); Venkatesh 2010 (mean SIA 1.20 ± 0.36 D MSICS versus 0.8 ± 0.24 D phacoemulsification) and Cook 2012 (median SIA -1.50 D MSICS versus -1.00 D phacoemulsification). At this time point, Gogate 2005a found mean astigmatism was almost equal in the two groups (1.1 D phacoemulsification group versus 1.2 D MSICs group). They also found that 47/185 participants in the phacoemulsification group and 40/187 in the small incision group had no astigmatism at all.
At six months postoperatively, Ruit 2007 did not show any significant difference in keratometric astigmatism between the MSICS group (0.88 D) and the phacoemulsification group (0.70 D) (P = 0.12).
Cost evaluation and surgical time
In Ruit 2007, phacoemulsification cases took 15.5 minutes each on average (cost USD 70 per case), whereas MSICS cases took nine minutes per case on average (cost USD 15 per case). Surgical time was reported in two studies, and was shorter in the MSICS group in both. Singh 2009 reported surgical time was less than six minutes in 11.2% of phacoemulsification and 84.9% of MSICS cases. Venkatesh 2010 reported mean surgical time of 8.8 +/- 3.4 minutes in the MSICS group and 12.2 +/- 4.6 minutes in the phacoemulsification group.
Summary of main results
The results are summarised in Summary of findings for the main comparison.
We defined a good visual outcome as presenting acuity of 6/12 or better. Presenting acuity was not reported by any trial and we have reported both best-corrected (BCVA) and uncorrected (UCVA) visual acuity. There was some evidence of a better visual outcome regarding UCVA at six weeks in participants in the phacoemulsification group versus the manual small incision cataract surgery (MSICS) group based on the results of three studies (Cook 2012; Gogate 2005a; Venkatesh 2010). However, there was no evidence of any difference in BCVA. Only one trial reported at longer time periods (six months), and found no difference in either corrected or uncorrected acuity.
We defined poor visual outcome as BCVA of less than 6/60. There were a small number of events reported in either group in any study, so it is uncertain as to whether there are differences between the two groups with respect to poor visual outcome.
The number of complications reported were also low for both techniques. Again this means the review is currently underpowered to detect a difference between the two techniques with respect to these complications. Although most studies did not report postoperative corneal oedema, in the two studies that did there was some evidence that phacoemulsification caused more immediate postoperative oedema than MSICS. Further investigation is required to assess whether this effect is dependent on the setting in which the studies were conducted: for example, levels of cataract severity and degree of surgical experience may be possible explanations of this effect
No data were reported on quality of life. The cost of phacoemulsification was more than four times greater per case than MSICS (Ruit 2007).
Overall completeness and applicability of evidence
The outcomes reported by the included studies differed widely, making it difficult to collate evidence from all studies. Any conclusions must therefore be treated with caution due to the small numbers involved. The majority of studies were performed in India and Nepal in high output surgical units, and thus these results can not easily be applied to other settings, such as in developed countries. The one study carried out in South Africa concluded that the outcomes of phacoemulsification were better for UCVA, BCVA and astigmatism. However, this study involved 15 surgeons of varying experience, so the results may reflect surgical expertise rather than surgical technique.
We considered quite a number of secondary outcomes, and it is possible that some significant findings might have arisen due to chance. As the number of events was low we did not observe many statistically significant findings and we think it unlikely that the overall conclusions of the review are based on chance findings.
Quality of the evidence
Overall we graded the quality of the evidence as low or very low. All studies included were randomised controlled trials (RCTs). However, the level of evidence for many outcomes was downgraded due to lack of data reported in assessing risk of bias, imprecision (wide confidence intervals) and inconsistency (for example, if only one study reported the outcome and consistency could therefore not be assessed). The main risk of bias was a lack of reporting of the cause of incomplete outcome data in many studies. Also, most of the studies had a short follow-up period with the longest follow-up time of six months only reported in one study. Therefore more data regarding long-term visual outcomes are needed to draw conclusions about the two surgical techniques.
Potential biases in the review process
We did not identify any obvious biases in the review process, although we did not have enough included studies (10 or more) to assess publication bias.
Agreements and disagreements with other studies or reviews
This review agrees with a recently published meta-analysis of six RCTs (Zhang 2013). Phacoemulsification was associated with improved uncorrected visual acuity compared to MSCIS, but both procedures resulted in similar best-corrected visual acuity.
A study comparing the cost of the two procedures (Muralikrishnan 2004) found MSICS to cost on average USD 17.03 per case, whereas phacoemulsification cost USD 25.55 per case. This study supports the finding that MSICS is less costly; however, their analyses included costs such as equipment, utilities, labour and materials in a very high volume setting, so the conclusions drawn are not directly comparable to the Ruit 2007 study.
Implications for practice
On the basis of eight RCTs included in this review the only significant difference found was in UCVA at three months which favoured phacoemulsification, but there were no differences in BCVA at three months or in either outcome at six months. There was no difference found in poor visual outcomes and complications between these two techniques for cataract surgery. However, due to a lack of available data the review is currently underpowered to detect differences for rarer complications. The major advantage of MSICS over phacoemulsification was the lower cost of this technique .
Implications for research
To be able to draw more comprehensive conclusions, more studies comparing MSICS and phacoemulsification are required. These need to have standardised reporting of outcomes enabling data from different studies to be pooled. In the absence of a formal core outcome set for such trials, we suggest that the primary outcomes we have included in this review (presenting visual acuity 6/12 or better and best corrected visual acuity worse than 6/60) should be reported as a minimum. However, as this review suggests that there may not be big differences in terms of visual outcome between these two interventions, future trials should collect information on vision-related quality of life and cost utility. Most of the trials included in this review had a relatively short follow-up period. We recommend a longer follow-up period ideally 12 months or more. We recognise that this may be difficult in some populations but it is important especially with regard to complications such as posterior capsule opacification which may become visually significant over a longer time course.
Iris Gordon at the Cochrane Eyes and Vision Group editorial base created and executed the electronic searches. We thank Clare Gilbert, Catey Bunce, Daniel Gore and Richard Wormald for their comments and Anupa Shah for editorial support. We would also like to thank Aeesha Malik for her work on the published protocol and earlier drafts of the review.
Richard Wormald (Co-ordinating Editor for CEVG) acknowledges financial support for his CEVG research sessions from the Department of Health through the award made by the National Institute for Health Research to Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology for a Specialist Biomedical Research Centre for Ophthalmology.
The views expressed in this publication are those of the authors and not necessarily those of the NIHR, NHS or the Department of Health.
Data and analyses
- Top of page
- Summary of findings [Explanations]
- Authors' conclusions
- Data and analyses
- Contributions of authors
- Declarations of interest
- Sources of support
- Differences between protocol and review
- Index terms
Appendix 1. CENTRAL search strategy
#1 MeSH descriptor Cataract
#2 MeSH descriptor Cataract Extraction
#3 MeSH descriptor Lens, Crystalline
#4 MeSH descriptor Lenses, Intraocular
#5 MeSH descriptor Lens Implantation, Intraocular
#6 intraocular lens* or intra ocular lens* or IOL*
#7 (#1 OR #2 OR #3 OR #4 OR #5 OR #6)
#8 MeSH descriptor Phacoemulsification
#10 phaco or phako
#11 (#8 OR #9 OR #10)
#12 manual near/3 small near/3 incision near/3 cataract*
#13 MISICS or SICS
#14 MeSH descriptor Capsulorhexis explode all trees
#15 continuous near/3 curvilinear near/3 capsulor*hexis
#16 continuous near/3 circular near/3 capsulor*hexis
#17 CCC or CCS
#18 can opener near/5 capsulotom*
#20 (#12 OR #13 OR #14 OR #15 OR #16 OR #17 OR #18 OR #19)
#21 (#7 AND #11 AND #20)
Appendix 2. MEDLINE (OvidSP) search strategy
1. randomized controlled trial.pt.
2. (randomized or randomised).ab,ti.
9. exp animals/
10. exp humans/
11. 9 not (9 and 10)
12. 8 not 11
13. exp cataract/
14. cataract extraction/
15. exp lens crystalline/
16. exp lenses intraocular/
17. lens implantation intraocular/
18. (intraocular lens$ or intra ocular lens$ or IOL$).tw.
22. (phaco or phako).tw.
24. (manual adj3 small adj3 incision adj3 cataract$).tw.
25. (MISICS or SICS).tw.
27. (continuous adj3 curvilinear adj3 capsulorhexis).tw.
28. (continuous adj3 circular adj3 capsulorhexis).tw.
29. (continuous adj3 curvilinear adj3 capsulor?hexis).tw.
30. (CCC or CCS).tw.
31. (can opener adj5 capsulotom$).tw.
34. 19 and 23 and 33
35. 12 and 34
The search filter for trials at the beginning of the MEDLINE strategy is from the published paper by Glanville et al (Glanville 2006).
Appendix 3. EMBASE (OvidSP) search strategy
1. exp randomized controlled trial/
2. exp randomization/
3. exp double blind procedure/
4. exp single blind procedure/
7. (animal or animal experiment).sh.
9. 7 and 8
10. 7 not 9
11. 6 not 10
12. exp clinical trial/
13. (clin$ adj3 trial$).tw.
14. ((singl$ or doubl$ or trebl$ or tripl$) adj3 (blind$ or mask$)).tw.
15. exp placebo/
18. exp experimental design/
19. exp crossover procedure/
20. exp control group/
21. exp latin square design/
23. 22 not 10
24. 23 not 11
25. exp comparative study/
26. exp evaluation/
27. exp prospective study/
28. (control$ or prospectiv$ or volunteer$).tw.
30. 29 not 10
31. 30 not (11 or 23)
32. 11 or 24 or 31
33. exp cataract/
34. exp cataract extraction/
35. exp lens/
36. exp lens implant/
37. exp lens implantation/
38. (intraocular lens$ or intra ocular lens$ or IOLS).tw.
40. exp phacoemulsification/
42. (phaco or phako).tw.
44. (manual adj3 small adj3 incision adj3 cataract$).tw.
45. (MISICS or SICS).tw.
47. (continuous adj3 curvilinear adj3 capsulorhexis).tw.
48. (continuous adj3 circular adj3 capsulorhexis).tw.
49. (continuous adj3 curvilinear adj3 capsulor?hexis).tw.
50. (CCC or CCS).tw.
51. (can opener adj5 capsulotom$).tw.
54. 39 and 43 and 53
55. 32 and 54
Appendix 4. LILACS search strategy
cataract$ and phaco$ or phako$ and manual small incis$ or MISICS or SICS or capsulorhexis or capsulorrhexis
Appendix 5. Web of Science CPCI-S search strategy
#17 #3 and #6 and #16
#16 #7 or #8 or #9 or #10 or #11 or #12 or #13 or #14 or #15
#15 TS=can opener capsulotom*
#14 TS=(CCC or CCS)
#13 TS=(continuous circular capsulorrhexis)
#12 TS=(continuous circular capsulorhexis)
#11 TS=(continuous curvilinear capsulorrhexis)
#10 TS=(continuous curvilinear capsulorhexis)
#8 TS=(MISICS or SICS)
#7 TS=(manual small incision)
#6 #4 or #5
#5 TS=(phaco or phako)
#4 TS=(phacoemulsification or phakoemulsification)
#3 #1 OR #2
#2 TS=(intraocular lens* or intra ocular lens* or IOL*)
Appendix 6. metaRegister of Controlled Trials search strategy
cataract AND phacoemulsification
Appendix 7. ClinicalTrials.gov search strategy
cataract AND phacoemulsification
Appendix 8. ICTRP search strategy
phacoemulsification = Condition AND manual or MISICS or SICS or capsulorhexis or capsulorrhexis = Intervention
Contributions of authors
Conceiving the review: YR
Designing the review: YR, JE
Co-ordinating the review: YR, JE
Data collection for the review:
- Designing electronic search strategies: Cochrane Eyes and Vision Group editorial base
- Undertaking manual searches:
- Screening search results: YR, JE, SdeS
- Organising retrieval of papers:
- Screening retrieved papers against inclusion criteria: YR, SdeS
- Appraising quality of papers: YR, SdeS, JE
- Extracting data from papers: YR, SdeS, JE
- Writing to authors of papers for additional information: YR
- Providing additional data about papers: SdeS, YR
- Obtaining and screening data on unpublished studies: SdeS, YR
Data management for the review:
- Entering data into Review Manager 5: JE, YR, SdeS
- Checking data entered into Review Manager 5: YR, JE, SdeS
Analysis of data: JE
Interpretation of data:
- Providing a methodological perspective: JE
- Providing a clinical perspective: YR, SdeS
- Providing a policy perspective: YR, SdeS
Writing the review: YR, SdeS, JE
Performing previous work that was the foundation of the current study: YR, JE
Declarations of interest
Sources of support
- No sources of support supplied
- Sightsavers, UK.
Differences between protocol and review
Primary outcome "presenting visual acuity 6/12 or better"
No study reported presenting visual acuity so we report both uncorrected and best-corrected acuity. Most studies reported 6/18 or better outcomes and we have used this to indicate 'good functional vision'.
Unit of analysis
The main unit of analysis issue is how the trial investigators dealt with two eyes. There were several options here: a trial may randomise people to the intervention groups and then apply the intervention and/or measure the outcome in one eye (study eye) or both eyes. However, if the intervention had been applied to both eyes, it would have been incorrect to analyse eyes without taking into account the fact that the eyes for a person are not independent. Alternatively a trial may randomly allocate eyes to an intervention so each person had a different intervention in each eye. In this case, the pairing would have to be taken into account in the analysis. In the protocol for this review, if the trial had been incorrectly analysed, we planned to contact the trial investigators for further information to enable calculation of a design effect (Perera 2007). However, in the event this was not necessary.
Assessment of reporting biases
The main reporting biases that we planned to consider were publication bias and outcome reporting bias. Currently there are not enough trials included in the review to assess publication bias.When there are enough trials (10 or more) we will do a funnel plot to see if small studies report different effects, one explanation for which could be publication bias
We planned to do a sensitivity analysis excluding trials at high risk of bias and investigating the impact of missing data. However, currently there are not enough data to enable this.
'Summary of findings' tables
This was not specified in the protocol.
The original published Cochrane review 'Riaz Y, Mehta JS, Wormald R, Evans JR, Foster A, Ravilla T, Snellingen T. Surgical interventions for age-related cataract. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD001323. DOI: 10.1002/14651858.CD001323.pub2' has been divided into three smaller reviews each using the same outcome measures as the original review but only comparing two surgical methods within each review. The interventions being compared are ECCE, MSICS and phacoemulsification. Intracapsular extraction (ICCE) is no longer included in the reviews as this technique is no longer used as a primary procedure.
Medical Subject Headings (MeSH)
*Lenses, Intraocular; Age Factors; Cataract Extraction [*methods]; Lens Implantation, Intraocular [*methods]; Phacoemulsification [methods]; Posterior Eye Segment; Randomized Controlled Trials as Topic; Visual Acuity
MeSH check words
* Indicates the major publication for the study