Methodological quality of the review: Medium confidence
Author: Shi C, Yuan J, Zee B.
Region: Australia, Turkey, China, United States of America (USA) and United Kingdom (UK)
Sector: Service delivery
Subsector: Quality of clincial care
Equity focus: Not stated
Review type: Other review
Quantitative synthesis method: Meta-analysis
Qualitative synthesis method: Not applicable
Phacoemulsification under local anesthesia is regarded as the major surgery for cataract treatment. Recent research has compared the pain perception between the first eye and the second eye during phacoemulsification. However, these studies have also yielded controversial findings.
To investigate the difference in the pain perception between the first and second eyes during phacoemulsification.
A total of eight studies were included in the meta-analysis. Two studies were conducted in Australia, two studies in Turkey, two studies in China, one study in the USA, and one study in the UK. The sample size was in the range of between 38 and 268.
The meta-analysis of seven studies comparing the pain scores assessed shortly following the phacoemulsification under local anesthesia showed that there were statistical differences in pain values between the first and the second eyes (WMD: 0.69; 95% CI: 0.40, 0.98; P<0.0000). Among these studies, authors reported high heterogeneity (I2=80%). Excluding one study at a time, the heterogeneity is still kept at a high level and overall effect showed no obvious change.
Authors also carried out an analysis of the pain scores only under the topical anesthesia as one of the subgroups. Four of seven studies were included, which also showed a difference (WMD: 1.08; 95% CI: 0.79, 1.36; P<0.00001) with low heterogeneity (I2=0%). Sensitivity analysis also showed the consistent result (WMD: 1.12; 95% CI: 0.76, 1.48; P<0.00001). Authors found a significant statistical difference in anxiety values between the first and the second eyes (SMD: -0.40; 95% CI: -0.64, -0.16; P=0.001) with low heterogeneity (I2=6%).
No evidence of publication bias was observed by the authors for the outcome of pain score on the day of surgery (Egger test P=0.59).
Authors concluded that patients experienced more pain in the surgery of the second eye than that of the first eye, which probably related to lower anxiety before the second surgery. This suggests that preoperative intervention to reduce the perceived pain during second eye cataract surgery should be considered.
Authors searched the database of PubMed, Embase and Cochrane to obtain eligible studies published up to 5 October, 2018. In addition, authors carried out a manual search of the references of associated studies to include more studies. Searches were conducted to identidy studies written in English only.
The following three selection criteria were used to identify the published studies for inclusion in this meta-analysis: First, authors used prospective observational studies or cohort studies; second, trials counted on the cataract patients who went through phacoemulsification under local anesthesia; third, the trials compared pain scores by visual analogue scale (VAS) between the first and the second eyes. Evaluation of the methodological quality of eligible comparative studies was undertaken based on Newcastle-Ottawa Scale (NOS).
Authors used Review Manager 5.3 to carry out statistical analysis. For continuous measurements, the weighted mean difference (WMD) and standard mean difference (SMD) with 95% confidence interval (CI) was used as the effect estimate. I2 was regarded as the evaluation of heterogeneity among studies, and publication bias was assessed using funnel plots and Egger test. Additionally, reviewers assessed the impact of each individual study through the exclusion of the studies one at a time.
Authors did not assess applicability/external validity of findings. They note that present meta-analysis shows that patients have more pain in the second surgery, which is explained by the assumption that patients who have successfully undergone the first eye surgery are likely to have less anxiety and expect lower pain perception for the second eye surgery. In order to apply these findings externally, some limitations of included studies in this review need to be taken into consideration: the pain scores on the first postoperative day, as well as the anxiety scores. were only obtained from two studies.
Authors did not discuss the applicability of findings to low and middle income countries.
Summary of quality assessment:
Overall, medium confidence was attributed to the conclusions about the effects of this review. Authors used rigorous methods to synthesise and pool data together. However, authors did not conduct thorough searches to ensure that all relevant studies were included in the review (potential publication bias and language bias).
Shi C, Yuan J, Zee B. Pain Perception of the First Eye versus the Second Eye during Phacoemulsification under Local Anesthesia for Patients Going through Cataract Surgery: A Systematic Review and Meta-Analysis. J Ophthalmol. 2019; 2019: 4106893.