- There are probably no clinically important differences between the two methods of cataract surgery in terms of complications, visual acuity (ability to distinguish shapes and objects at a given distance) and quality of life.
- Femtosecond laser-assisted cataract surgery (FLACS) was more expensive and there was some evidence that phacoemulsification cataract surgery (PCS) may be more cost-effective.
- There were differences in how studies reported outcomes: standardised outcome reporting would help future comparisons.
What is a cataract?
Cataract is clouding of the lens inside the eye. It is the leading cause of blindness in the world.
What is cataract surgery?
Cataract surgery is one of the most performed operations globally. During standard surgery, the surgeon opens the front of the lens capsule (the lens outer layer or ‘skin’), removes the cloudy lens material inside the capsule and places a clear artificial lens in the remaining capsular bag. The aim of femtosecond laser-assisted cataract surgery (FLACS) is to provide more precise control over the steps involved in cataract surgery. By being more precise, it is plausible that this could lead to better outcomes or higher safety for people undergoing cataract surgery.
What did we want to find out?
The aim of this Cochrane Review was to find out what the benefits and harms of FLACS are compared with standard ultrasound PCS.
What did we do?
We searched for studies that compared PCS to FLACS in people with age-related cataracts. We compared and summarised the results of the studies and rated our confidence in the evidence, based on factors such as study methods and study size.
What did we find?
The analysis included 42 studies that involved 5831 people. The studies were conducted in countries around the world; most were done in Europe (25). All of these studies compared FLACS with PCS for people with cataracts. Sixteen of the studies were either funded by the manufacturer of the laser machine or the investigators reported financial links with the manufacturer.
Overall, there was some uncertainty as to whether FLACS reduces the number of tears to the lens capsule because there were very few cases of capsule tears in both the manual and laser-assisted cataract surgeries in these studies. Based on the data available, any difference in capsule complications is expected to be small. The capsule is a delicate membrane that originally covered the natural lens and holds the artificial lens following surgery. Tears in the capsule can adversely affect the visual outcomes following cataract surgery and may necessitate further surgery. Other complications were also infrequent for both laser-assisted and standard cataract surgery. Based on the data available, any difference in postoperative visual outcomes is also expected to be small.
Only three studies reported the effect of the operations on people’s quality of life and there is probably little or no difference when comparing FLACS and PCS.
FLACS was the more expensive option and two studies reported that it was less cost-effective.
What are the limitations of the evidence?
Our confidence in the evidence is low because of concerns about the fact that patients and assessors were aware of which treatment they were receiving or providing, respectively. Furthermore, not all of the studies provided data about everything we were interested in. Lastly, the evidence is also based on few cases of events in some areas.
How up-to-date is this evidence?
We searched for studies that had been published up to 10 May 2022.
This review of 42 studies provides evidence that there is probably little or no difference between FLACS and PCS in terms of intraoperative and postoperative complications, postoperative visual acuity and quality of life. Evidence from two studies suggests that FLACS may be the less cost-effective option. Many of the included studies only investigated very specific outcome measures such as effective phacoemulsification time, endothelial cell count change or aqueous flare, rather than those directly related to patient outcomes. Standardised reporting of complications and visual and refractive outcomes for cataract surgery would facilitate future synthesis, and guidance on this has been recently published.
Cataract is the leading cause of blindness in the world and, as such, cataract surgery is one of the most commonly performed operations globally. Surgical techniques have changed dramatically over the past half century with associated improvements in outcomes and safety. Femtosecond lasers can be used to perform the key steps in cataract surgery, such as corneal incisions, lens capsulotomy and fragmentation. The potential advantage of femtosecond laser-assisted cataract surgery (FLACS) is greater precision and reproducibility of these steps compared to manual techniques. The disadvantages are the costs associated with FLACS technology.
To compare the effectiveness and safety of FLACS with standard ultrasound phacoemulsification cataract surgery (PCS) by gathering evidence from randomised controlled trials (RCTs).
We searched the Cochrane Central Register of Controlled Trials (CENTRAL; which contains the Cochrane Eyes and Vision Trials Register; 2022, Issue 5); Ovid MEDLINE; Ovid Embase; LILACS; the ISRCTN registry; ClinicalTrials.gov; the WHO ICTRP and the US Food and Drug Administration (FDA) website. We did not use any date or language restrictions in the electronic searches for trials. We last searched the electronic databases on 10 May 2022.
We included RCTs where FLACS was compared to PCS.
Three review authors independently screened the search results, assessed risk of bias and extracted data using the standard methodological procedures expected by Cochrane. The primary outcome for this review was intraoperative complications in the operated eye, namely anterior capsule, and posterior capsule tears. The secondary outcomes included corrected distance visual acuity (CDVA), quality of vision (as measured by any validated patient-reported outcome measure (PROM)), postoperative cystoid macular oedema complications, endothelial cell loss and cost-effectiveness. We assessed the certainty of the evidence using GRADE.
We included 42 RCTs conducted in Europe, North America, South America and Asia, which enrolled a total of 7298 eyes of 5831 adult participants. Overall, the studies were at unclear or high risk of bias. In 16 studies the authors reported financial links with the manufacturer of the laser platform evaluated in their studies. Thirteen of the studies were within-person (paired-eye) studies with one eye allocated to one procedure and the other eye allocated to the other procedure. These studies were reported ignoring the paired nature of the data.
There was low-certainty evidence of little or no difference in the odds of developing anterior capsular tears when comparing FLACS and PCS (Peto odds ratio (OR) 0.83, 95% confidence interval (CI) 0.40 to 1.72; 5835 eyes, 27 studies) There was one fewer anterior capsule tear per 1000 operations in the FLACS group compared with the PCS group (95% CI 4 fewer to 3 more).
There was low-certainty evidence of lower odds of developing posterior capsular tears with FLACS compared to PCS (Peto OR 0.50, 95% CI 0.25 to 1.00; 5767 eyes, 26 studies). There were four fewer posterior capsule tears per 1000 operations in the FLACS group compared with the PCS group (95% CI 6 fewer to same).
There was moderate-certainty evidence of a very small advantage for the FLACS arm with regard to CDVA at six months or more follow-up, (mean difference (MD) -0.01 logMAR, 95% CI -0.02 to 0.00; 1323 eyes, 7 studies). This difference is equivalent to 1 logMAR letter between groups and is not thought to be clinically important.
From the three studies (1205 participants) reporting a variety of PROMs (Cat-PROMS, EQ-5D, EQ-SD-3L, Catquest9-SF and patient survey) up to three months following surgery, there was moderate-certainty evidence of little or no difference in the various parameters between the two treatment arms.
There was low-certainty evidence of little or no difference in the odds of developing cystoid macular oedema when comparing FLACS and PCS (Peto OR 0.84, 95% CI 0.56 to 1.28; 4441 eyes, 18 studies). There were three fewer cystoid macular oedema cases per 1000 operations in the FLACS group compared with the PCS group (95% CI 10 fewer to 6 more).
In one study the incremental cost-effectiveness ratio (ICER) (cost difference divided by quality-adjusted life year (QALY) difference) was GBP £167,620 when comparing FLACS to PCS. In another study, the ICER was EUR €10,703 saved per additional patient who had treatment success with PCS compared to FLACS. Duration ranged from three minutes in favour of FLACS to eight minutes in favour of PCS (I2 = 100%, 11 studies) (low-certainty evidence).
There was low-certainty evidence of little or no important difference in endothelial cell loss when comparing FLACS with PCS (MD 12 cells per mm2 in favour of FLACS, 95% CI -40 to 64; 1512 eyes, 10 studies).