Local anaesthetics in cataract surgery: do eye drops work better with, or without, an injection of anaesthetic?

What are cataracts?

A cataract starts when cloudy patches develop on the lens of your eye. The lens is a small, clear disc inside the eye that focuses light rays to make clear images of objects seen. As the cloudy patches get bigger over time, sight becomes misty and blurred. Cataracts are more common in older people, and can affect your ability to do everyday activities, such as driving. Untreated cataracts will lead to blindness.

How are cataracts treated?

Surgery is the only way to improve your eyesight if you have cataracts. In cataract surgery (phacoemulsification), a tiny cut is made in your eye; the old, cloudy lens is removed and a new, plastic lens is put in its place.

During the operation you are usually awake. Doctors use eye drops containing a numbing medicine (local anaesthetic) to stop the nerves in your eye sending pain signals to your brain during the operation. Sometimes, in addition to anaesthetic eye drops, lidocaine (a type of local anaesthetic) may be injected inside your eye. This may reduce pain during and after the operation.

Why did we do this review?

In this Cochrane Review, we wanted to identify the potential benefits and harms of lidocaine injection into the eye in addition to anaesthetic eye drops during cataract surgery.

What did we do?

In February 2020, we searched for studies that looked at the effects of giving a lidocaine injection and anaesthetic eye drops, compared with giving anaesthetic eye drops alone, during cataract surgery. We looked for randomized controlled studies, a type of study in which treatments are given at random to people in the people in the study because these studies usually give the most reliable evidence about treatments.

Search date: we included evidence published up to 4 February 2020.

What we found

We found 13 studies in 2355 adults, aged 34 to­ 95 years, who had cataract surgery in one or both eyes. The studies were conducted in hospitals and eye day-care centres in the USA, Canada, Australia, the UK, Italy, Taiwan, Singapore, India, and Pakistan.

What are the results of the review?

Compared with giving anaesthetic eye drops alone, lidocaine injection with anaesthetic eye drops probably:

· reduced the level of pain experienced during the operation;

· reduced the number of people who said they felt any pain during their operation;

· did not reduce the level of pain people said they felt after the operation; and

· did not cause additional eye damage (measured before the operation and after 1 and 12 months).

Lidocaine injection with anaesthetic eye drops may make little or no difference to:

· how many people needed extra anaesthesia during their operation; and

· people's satisfaction with their cataract surgery (we are uncertain about this result because it is based on only one study).

The numbers of unwanted (adverse) effects associated with local anaesthetics were similar between people who had eye drops alone and those who had eye drops and a lidocaine injection. But we are uncertain about this result because the type of study we looked at may not have been the best to assess unwanted effects.

Our confidence in the results

We are moderately confident (certain) in most of our results. However, we only looked at a small number of studies, and in some studies the doctors were aware of which treatment they were giving, which could have affected the study's results. Our results may change if more research becomes available.

Conclusions

Lidocaine injection plus anaesthetic eye drops probably reduced the level of pain during a cataract operation more than using anaesthetic eye drops alone, and led to fewer people reporting pain during the operation. However, pain ratings for this operation were generally low both with and without a lidocaine injection, so this difference may not be clinically important.

Lidocaine injection plus anaesthetic eye drops did not reduce the level of pain people said they felt after their operation. Although lidocaine injection did not cause additional eye damage, we are uncertain whether its use causes more unwanted effects than eye drops alone.

Authors' conclusions: 

There is moderate-quality evidence that supplementation of topical anaesthesia with intracameral lidocaine 0.5% to 1% for phacoemulsification cataract surgery in adults reduces participant perception of intraoperative pain. The odds of experiencing any pain (as opposed to no pain) were 60% less for the topical anaesthesia plus intracameral lidocaine group versus the topical anaesthesia-only group. However, the numerical amplitude of the effect may not be of great clinical significance on the continuous pain score scale. Generally, the pain scores were consistently low for both techniques. We found moderate-quality evidence that there is no additional benefit of intracameral lidocaine on postoperative pain. There is insufficient evidence to determine the impact on participant satisfaction and need for additional intraoperative anaesthesia due to low-quality evidence. There is moderate-quality evidence that intracameral lidocaine supplementation does not increase measures of intraocular toxicity, specifically loss of corneal endothelial cells. There is low-quality evidence that the incidence of intraoperative adverse events is unchanged with intracameral lidocaine supplementation, but as RCTs are not the optimum medium for looking at this, this result should be interpreted with caution.

Further research specifically investigating the adverse effects of intracameral anaesthesia might help to better determine its safety profile. Economic evaluations would also be useful for detailing cost implications.

Read the full abstract...
Background: 

Phacoemulsification cataract surgery is usually performed in adults under local anaesthesia. Topical anaesthesia, which involves instilling anaesthetic drops to the ocular surface prior to and during surgery, has found large acceptance internationally. It is safe and allows for rapid patient turnover and visual recovery. Some surgeons have supplemented topical anaesthesia with intracameral lidocaine, reasoning that this may further reduce intraoperative pain, particularly during surgical stages involving manipulation of intraocular structures and rapid changes in fluid dynamics. This review, originally published in 2006 and updated in 2020, explores the efficacy and safety of using supplementary intracameral lidocaine in phacoemulsification cataract surgery.

Objectives: 

To assess whether supplementing topical anaesthesia with intracameral lidocaine for phacoemulsification cataract surgery in adults reduces intraoperative and postoperative pain, and to assess differences in participant satisfaction, need for additional intraoperative anaesthesia, surgeon satisfaction, measures of intraocular toxicity, and adverse effects attributable to choice of anaesthesia.

Search strategy: 

We searched CENTRAL, MEDLINE, Embase, LILACS BIREME iAH, and six trial registries on 4 February 2020. We also searched the reference lists of identified studies. There were no language restrictions.

Selection criteria: 

We included only randomized controlled trials (RCTs) where participants underwent phacoemulsification for age-related cataract under topical anaesthesia with or without intracameral lidocaine either in two eyes of the same participant, or in different participants. We also included studies that used oral or intravenous sedation in addition to local anaesthesia.

Data collection and analysis: 

Two review authors independently extracted data and assessed trial methodological quality using standard Cochrane procedures.

Main results: 

We identified five new RCTs in this updated review. We included a total of 13 trials in the review, conducted in the UK, the USA, Australia, Italy, Canada, Taiwan, Singapore, India, and Pakistan, and comprising 2388 eyes of 2355 participants (one study was a paired-eye study with each participant acting as their own control). The age range of participants was 34 to 95 years. We excluded studies that only included low-risk participants and excluded more difficult operative cases, for example hard lens nuclei or small pupils. We excluded studies assessing only participants with Fuchs' endothelial dystrophy.

We judged one study as at high risk for selection bias. We assessed five studies as having an unclear risk of bias for random sequence generation and seven studies an unclear risk of bias for allocation concealment. We judged three studies as at high risk of performance bias, as the surgeon was not blinded, and two studies as at unclear risk of bias for this domain. No studies were judged as at high risk for detection bias, but five studies were judged to have an unclear risk of bias for this domain. We judged all 13 included studies to have a low risk of attrition bias and an unclear risk of reporting bias.

Data from eight RCTs favoured topical anaesthesia plus intracameral lidocaine 0.5% to 1% over topical anaesthesia alone for reducing intraoperative pain when measured using a 10-point visual analogue scale, analysed as a continuous outcome. Mean pain score was 0.26 lower in the supplemental intracameral lidocaine group (95% confidence interval (CI) −0.39 to −0.13, 1692 eyes, moderate-quality evidence). Data from seven RCTs favoured supplemental intracameral lidocaine for reducing intraoperative pain when measured as a dichotomous outcome. The odds ratio of experiencing any pain was 0.40 versus the topical anaesthesia-only group (95% CI 0.29 to 0.57, 1268 eyes, moderate-quality evidence). Data from four RCTs did not show any additional benefit on postoperative pain when measured using a 10-point visual analogue scale (mean difference 0.12 points, 95% CI −0.29 to 0.05, 751 eyes, moderate-quality evidence).

The impact on participant satisfaction was uncertain as only one small study investigated this outcome. The study suggested no difference between groups (mean difference 0.1 points, 95% CI −0.47 to 0.27, 60 eyes, low-quality evidence).

Data from seven RCTs did not demonstrate a difference between groups in the need for additional intraoperative anaesthesia (odds ratio 0.88, 95% CI 0.56 to 1.39, 1194 eyes of 1161 participants; low-quality evidence), although this result is uncertain.

A variety of measures were reported relating to possible intraocular toxicity. Data from four RCTs did not demonstrate a difference between groups in mean percentage corneal endothelial cell count change from pre- to postoperatively (mean difference 0.89%, 95% CI −1.12% to 2.9%, 254 eyes of 221 participants, moderate-quality evidence).

Synthesis of the evidence from eight RCTs identified no difference in intraoperative adverse events between groups (odds ratio 1.00, 95% CI 0.32 to 3.16, 1726 eyes, low-quality evidence). This result should be interpreted with caution, mainly due to a lack of clear definitions of adverse events, low numbers of events, heterogeneity between studies, and large confidence intervals. Large observational studies may have been more appropriate for looking at this outcome.

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