Using skew-symmetric mixed models for investigating the effect of different diabetic macular edema treatments by analyzing central macular thickness and visual acuity responses

Marjan Mansourian, Anoshirvan Kazemnejad, Iraj Kazemi, Farid Zayeri, Masoud Soheilian


  • BACKGROUND: Diabetic Macular Edema (DME) is one of the major causes of visual loss and increase in central macular thickness (CMT). The aim of this study was to determine the efficacy of a single intravitreal injection of bevacizumab (IVB) alone or in combination with intravitreal triamcinolone acetonide (IVB/IVT) versus macular laser photocoagulation (MPC) as primary treatment for DME when confounders were considered.
  • METHODS: Skew-symmetric bivariate mixed modeling according to best corrected visual acuity (BCVA) and CMT was done on the data of 103 diabetic patients from ophthalmic research center of Labbafinejad medical center (Tehran, Iran) to determine the best DME treatment by adjusting the effect of confounders.
  • RESULTS: Although there was no significant difference between IVB/IVT (p > 0.05), these two treatments increased BCVA and decreased CMT better than MPC (p < 0.05). The following three groups showed better treatment responses: 1) women, 2) patients with more diabetes duration, 3) patients whose CMT were higher and VA were lower at the beginning of the clinical trial.
  • CONCLUSIONS: Using skew-symmetric mixed effect model as updated statistical method in presence of asymmetric or outlier data, we received different results compared to the same investigation on this study by analyzing BCVA and CMT simultaneously. This research demonstrated the effect of IVB alone or in combination with intravitreal IVB/IVT on visual power and decreasing CMT during follow up.
  • KEYWORDS: Best-Corrected Visual Acuity, Central Macular Thickness, Diabetic Macular Edema, Skew-symmetric Mixed Models.

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