Posterior Capsule Opacification after Cataract Surgery via Implantation with Hydrophobic Acrylic Lens Compared with Silicone Intraocular Lens: A Systematic Review and Meta-Analysis

Hydrophobic acrylic intraocular lens (IOL) is the most popular material in cataract surgery. Posterior capsule opacification (PCO) is a long-term complication of cataract surgery. It can impair vision and adversely affect the prognosis of IOL delamination. The objective of this study was to perform a systematic review and meta-analysis to provide an updated evaluation of long-term complications and visual function after implantation with hydrophobic acrylic and silicone intraocular lenses. PubMed, Embase, and Cochrane Library were searched from January 2000 until March 2021. Randomized controlled trials (RCTs) and retrospective studies were finally included. The main outcomes were PCO value and neodymium-doped yttrium aluminum garnet (Nd : YAG) capsulotomy rate. Subgroup analysis was performed to compare hydrophobic acrylic and silicone IOLs during the follow-up period. Sensitivity analysis was also performed. The meta-analysis included a total of 17 studies. When the follow-up period was considered, the results of the analysis revealed higher PCO value (Group 3: standardized mean difference (SMD), −0.59; 95% confidence interval (CI), −0.90 to −0.28) and Nd : YAG capsulotomy rate (Group 3: risk ratio (RR), 0.60; 95% CI, 0.40–0.89) for hydrophobic acrylic IOLs than silicone IOLs during a long-term (≥6 years) follow-up. In conclusion, both the PCO value and the Nd : YAG capsulotomy rates were higher in hydrophobic acrylic IOLs group than the silicone IOLs group at long-term use (more than 6 years) after implantation.


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Effect measures 12 Specify for each outcome the effect measure(s) (e.g. risk ratio, mean difference) used in the synthesis or presentation of results. 3, 4 Synthesis methods 13a Describe the processes used to decide which studies were eligible for each synthesis (e.g. tabulating the study intervention characteristics and comparing against the planned groups for each synthesis (item #5)).

N/A
13b Describe any methods required to prepare the data for presentation or synthesis, such as handling of missing summary statistics, or data conversions.
3 13c Describe any methods used to tabulate or visually display results of individual studies and syntheses. N/A 13d Describe any methods used to synthesize results and provide a rationale for the choice(s). If meta-analysis was performed, describe the model(s), method(s) to identify the presence and extent of statistical heterogeneity, and software package(s) used.

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13e Describe any methods used to explore possible causes of heterogeneity among study results (e.g. subgroup analysis, meta-regression). 4

Section and Topic
Item # Checklist item Location where item is reported (page#) 13f Describe any sensitivity analyses conducted to assess robustness of the synthesized results. 3 Reporting bias assessment 14 Describe any methods used to assess risk of bias due to missing results in a synthesis (arising from reporting biases). 3 Certainty assessment 15 Describe any methods used to assess certainty (or confidence) in the body of evidence for an outcome. N/A

Study selection
16a Describe the results of the search and selection process, from the number of records identified in the search to the number of studies included in the review, ideally using a flow diagram.

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16b Cite studies that might appear to meet the inclusion criteria, but which were excluded, and explain why they were excluded.

Random sequence generation (selection bias) Low
Initially randomized into 3 groups based on IOL type. All enrolled eyes were randomly allocated using the sealedenvelope method.
Allocation concealment (selection bias) Low All enrolled eyes were randomly allocated using the sealedenvelope method. Blinding of participants and personnel (performance bias) Low Patients, examiners, and surgeons were masked.
Blinding of outcome assessment (detection bias) Low Patients, examiners, and surgeons were masked.
Incomplete outcome data (attrition bias) Low "Of the 300 eyes, 10 in the PMMA IOL group, 17 in the silicone IOL group, and 4 in the acrylic IOL group were lost to follow-up. Thus, 269 eyes completed a 2 year follow-up and were available for analysis" Selective reporting (reporting bias) Low "The study protocol was approved by the Institutional Review Board, and informed consent was obtained from each patient" Other bias Low Not likely

Hayashi K 2007 [31]
Bias Judgement Support for judgement

Random sequence generation (selection bias) Low
"The controller of this clinical trial generated a randomization code with equal numbers using random number tables, and, to ensure allocation concealment, the assignment schedule was kept concealed until all data were collected" Allocation concealment (selection bias) Low All enrolled patients were randomly assigned the day before surgery to one of two groups. Blinding of participants and personnel (performance bias) Low All patients and examiners were masked as to randomization.
Blinding of outcome assessment (detection bias) Low "The operating room personnel who allocated the IOLs to the patients were unaware of the purpose of this study. The examiners were also unaware of the type of IOL used because the two IOLs are the same in appearance. Furthermore, because the controller of this clinical trial assignment schedule was kept concealed until the end of the study, the data analyst, who was the surgeon, did not know the type of IOL used" Incomplete outcome data (attrition bias) Low "Of the 100 patients enrolled, nine were lost to follow-up during the 36-month period: one patient died and two were hospitalized for an unrelated cause, one moved from the area, and five did not appear for reexamination because of an illness or scheduling conflict. In addition, in two patients the Scheimpflug image obtained was difficult to analyze. Therefore, 89 patients (89%) remained for analysis"  (10), no surgery or adverse events before second surgery (7), refused further participation (12), and other (12) Allocation concealment (selection bias) Unclear "The IOL type for the first-operated eye of each patient was assigned randomly before surgery" No mention how to be assigned randomly. Blinding of participants and personnel (performance bias) Low Double-blind Blinding of outcome assessment (detection bias) Unclear Not reported Incomplete outcome data (attrition bias) Low "Of the 52 patients who were included in the study, 43 patients were available 1 year after surgery. Nine patients were not available for follow-up examination (one patient died before the 1-year follow-up examination; three patients were excluded after the operation because they were not operated bilaterally, and five patients could not be reached). One patient in group 1 and three patients group 2 were excluded because the pupil dilation did not exceed the size of the capsulorrhexis edge, so 80 eyes of 40 patients were evaluated in each group" Selective reporting (reporting bias) Unclear "The Ethics Committee of the Medical University of Vienna approved the protocol. Patients gave informed consent before inclusion into the study" Other bias Low Not likely

Vock L, Crnej A 2009 [9]
Bias Judgement Support for judgement Random sequence generation (selection bias) Low Randomized by using numbers from a computer-generated list of random numbers.