Comment on: “Risk factors and incidence of macular edema in eyes with retinal vein occlusion after uneventful cataract surgery: The MEVO study”

Dear Editor, Sen et al.[1] performed a retrospective cohort study to evaluate the incidence and risk factors of postoperative macular edema (PME) in patients with retinal vein occlusion (RVO) who underwent uneventful cataract surgery. The study monitored 162 eyes during an average period of 13 months and revealed that PME developed in about 40% of cases, especially among diabetic patients and those who had cystoid macular edema (CME). The authors established that previous CME and diabetes served as strong risk factors for PME development and found that PME resulted in worse visual outcomes after surgery. The study provides important clinical knowledge about risk groups among RVO patients. However, several potential research boundaries need evaluation. First, the study[1] evaluated preoperative visual acuity (VA) measurements and VA results from 1 month and final follow-up points. The authors employed t-tests for assessing time point differences in their repeated measurements of the same variable, yet this approach is statistically inappropriate for such analyses. The appropriate statistical method to evaluate changes in a continuous variable across three or more time points should be repeated measures analysis of variance (ANOVA),[2] as it handles within-subject correlations to produce stronger temporal evaluation results. The application of multiple t-tests both increases the possibility of type I errors and prevents researchers from detecting temporal interaction effects. We believe the general findings about visual improvement will probably remain the same, but it remains crucial to implement correct statistical methods to validate and reproduce the study results. Second, the study[1] established PME as its primary outcome measure; however, 57.3% of study eyes showed preoperative CME diagnosis. The absence of fluid observed in OCT scans before surgery might indicate only a brief anatomical improvement instead of lasting remission of CME in those eyes. The observed postoperative edema in the study remains uncertain whether it constitutes new PME or it represents the re-emergence of preexisting CME. The unclear distinction between these clinical cases makes the outcome measurement less reliable because it merges different pathological processes. The high incidence of PME in RVO patients undergoing cataract surgery may stem from CME recurrence rather than surgical complications, thus potentially inflating the study’s PME rates. Third, the study[1] involved 72 patients with diabetes mellitus (44.44%) and recognized diabetes as a significant risk factor for PME. Nevertheless, the study lacked specific information about the glycemic control status of these patients, which restricts the capacity to evaluate the actual influence of diabetes on PME risk. It is well established that poor glycemic control, often assessed via glycated hemoglobin (HbA1c) levels, is associated with an increased occurrence of microvascular complications, including retinal vascular dysfunction.[3,4] A reasonable hypothesis suggests that diabetic patients who maintain well-controlled HbA1c levels might experience a reduced risk of developing PME, whereas those with inadequate glycemic control face a considerably elevated risk. This underscores the importance of identifying subgroups within the diabetic population that are at heightened risk. We recommend that future analyses include HbA1c data and perform subgroup analyses based on glycemic control to improve risk stratification and management. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.