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Medical prophylaxis and treatment of cystoid macular edema after cataract surgery: the results of a meta-analysis |
Rossetti L, Chaudhuri J, Dickersin K |
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Authors' objectives To determine the effectiveness of prophylactic medical intervention in reducing the incidence of cystoid macular oedema (CME), and the effectiveness of medical treatment for chronic CME after cataract surgery.
Searching MEDLARS (MEDLINE) was searched for RCTs on prophylaxis of CME using the MeSH 'macular edema', 'cystoid', 'cataract/complications' and the textword 'macular edema'. Reports published from 1966 to 1996 in English, French and German were retrieved. In addition, MEDLINE was searched for studies evaluating a treatment effect in patients with chronic aphakic and pseudophakic CME using the following MeSH: 'macular edema', 'cystoid', 'cyclooxygenase inhibitors', 'ketorolac', 'fenoprofen', 'indomethacin' and 'steroidal agents'. The bibliographies of the collated articles were inspected for additional pertinent reports.
Study selection Study designs of evaluations included in the reviewPublished reports of randomised controlled trials (RCTs). In the prophylactic medical interventions (n=15), the mean duration of follow-up was 4.6 months: follow-up was less than 3 months in 9 trials, from 3 to 6 months in 5 trials, and 18 months in 1 trial.
In the medical treatment interventions (n=4), the duration of treatment was 1.5 months in 1 study, 2 months in 2 studies and 3 months in 1 study. The mean duration of follow-up was 3.5 months.
Specific interventions included in the reviewFor the prophylactic medical interventions for surgically-induced CME, almost all studies tested cyclo-oxygenase inhibitors (COIs) as the test prophylactic intervention. In the trials investigating the efficacy of medical treatment for chronic CME, the types of treatment included various COIs, steroidal agents (local and systemic), acetazolamide, cycloplegic agents and hyperbaric oxygen.
Participants included in the reviewPatients experiencing aphakic or pseudophakic CME following cataract extraction were included, and articles had to report on at least ten patients. Studies evaluating patients with other types of macular oedema were excluded, unless the data were presented separately for the different types of oedema, as were those studies reporting on CME after other surgical procedures.
Outcomes assessed in the reviewThe incidence of angiographically diagnosed CME, defined as any amount of leakage on the angiogram; the incidence of clinically significant CME; and vision.
How were decisions on the relevance of primary studies made?Abstracts were reviewed by one of the authors to select potentially relevant articles. These were independently assessed by two authors and any disagreements were resolved.
Assessment of study quality Articles were assessed according to: sample size, a priori estimate of sample size, method of randomisation, masking of patients and assessor, and handling of withdrawals. The validity of the papers was assessed by two independent authors and any disagreements were resolved.
Data extraction The data were extracted by two independent authors.
Within the individual studies, the data were not extracted in an intention-to-treat format. However, the authors reported the percentage of withdrawals in each study.
Methods of synthesis How were the studies combined?Summary statistics relating to the incidence of angiographic and clinical CME were calculated using data from all of the RCTs. The effects of interventions were presented in terms of odds ratios (ORs). When the outcomes of interest were 'negative' (e.g. clinical CME), a value of less than 1.0 indicated that the odds of an adverse outcome were less in those given the test intervention than in those given the comparison intervention (e.g. placebo). Therefore, the test intervention showed a protective effect. Conversely, for 'positive' outcomes of interest, an OR of less than 1.0 indicated a 'harmful' effect.
The summary OR was calculated using the Mantel-Haenszel method, according to Peto (see Other Publications of Related Interest).
How were differences between studies investigated?Heterogeneity among studies was tested using the chi-squared statistic, where a P-value of less than or equal to 0.10 was considered to indicate heterogeneity.
Results of the review Fifteen RCTs involving 2,898 eyes examined the effectiveness of medical prophylaxis of CME, and 4 RCTs involving 187 eyes tested the effectiveness of medical treatment of chronic CME.
No significant heterogeneity was found among studies investigating prophylactic medical interventions or medical treatment for CME.
Summary ORs indicated that prophylactic intervention was effective in reducing the incidence of both angiographic CME (OR 0.36, 95% confidence interval, CI: 0.28, 0.45) and clinically-relevant CME (OR 0.49, 95% CI: 0.33, 0.73). There was also a significant positive effect on improving visual acuity (OR 1.97, 95% CI: 1.14, 3.41).
A combination of the results of the 4 RCTs testing medical therapy for chronic CME indicated a treatment benefit, in terms of improved visual acuity, by at least 2 Snellen lines (OR 2.67, 95% CI: 1.35, 5.30).
Authors' conclusions The results indicated that medical prophylaxis for aphakic and pseudophakic CME, and medical treatment for chronic CME, are beneficial. However, a well-designed RCT, using clinical CME and vision as outcomes, is needed to confirm this result because most of the RCTs performed to date have problems relating to quality,
CRD commentary The authors presented clear objectives.
The literature search could have been extended to include EMBASE and a handsearch. The authors stated that the search strategy used could have led to a publication bias.
Inclusion criteria were clearly stated. A thorough validity assessment was undertaken, but the extracted information was neither scored nor used.
The design and quality features of the RCTs were presented in a tabular format. Patient characteristics, such as age and gender, were not reported.
The primary studies were combined appropriately, and the conclusions appear to follow logically from the results.
Implications of the review for practice and research Additional research is required using clinical CME and vision as outcomes.
The authors suggest that a systematic review of this topic should be part of an ongoing system of reviews in ophthalmology that is kept up-to-date and can be used for setting treatment guidelines. Such a system has been proposed and is being undertaken by the Cochrane Collaboration.
Bibliographic details Rossetti L, Chaudhuri J, Dickersin K. Medical prophylaxis and treatment of cystoid macular edema after cataract surgery: the results of a meta-analysis. Ophthalmology 1998; 105(3): 397-405 Other publications of related interest Yusuf S, Peto R, Lewis J, Collins R, Sleight P. Beta blockade during and after myocardial infarction: an overview of the randomized trials. Prog Cardiovasc Dis 1985;27:335-71.
Indexing Status Subject indexing assigned by NLM MeSH Aphakia, Postcataract /etiology; Cataract Extraction /adverse effects; Chronic Disease; Cyclooxygenase Inhibitors /therapeutic use; Glucocorticoids /therapeutic use; Humans; Incidence; Macular Edema /drug therapy /etiology /physiopathology; Premedication; Pseudophakia /etiology; Randomized Controlled Trials as Topic; Visual Acuity /physiology AccessionNumber 11998000481 Date bibliographic record published 30/09/1999 Date abstract record published 30/09/1999 Record Status This is a critical abstract of a systematic review that meets the criteria for inclusion on DARE. Each critical abstract contains a brief summary of the review methods, results and conclusions followed by a detailed critical assessment on the reliability of the review and the conclusions drawn. |
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