Purpose: To assess the effect of initial central macular thickness (CMT) on the response to treatment in diabetic macular edema.
Methods: The data of 150 eyes of 129 patients with clinically significant diabetic macular edema and no previous treatment who had been randomly assigned in the original trial to 1 of the 3 groups, 1) intravitreal bevacizumab (IVB) group (50 eyes); 2) combined intravitreal bevacizumab and triamcinolone (IVB/IVT) group (50 eyes); and 3) macular laser photocoagulation group (50 eyes), were reevaluated. This time the data of the cases were reanalyzed based on their initial CMT. Accordingly, the original treatment groups were categorized into 3 subgroups: 1) <250 μm, 2) 250 μm to 349 μm, and 3) ≥350 μm. Visual acuity and CMT changes in response to different treatments were compared. Main outcome measures were changes in visual acuity and CMT at Weeks 6, 12, 24, and 36.
Results: At 6 weeks in all subgroups, mean visual acuity improvement in the IVB group was significantly greater than the other groups (P = 0.002, P = 0.003, P < 0.001, for subgroups of <250, 250-349, and ≥350 μm, respectively). At 12, 24, and 36 weeks in the subgroup >350 μm and at 24 weeks in the subgroup 250 μm to 349 μm, the difference of mean visual acuity changes among the groups reached to a significant level (P = 0.010, P = 0.028, P < 0.001, and P < 0.001, respectively) in favor of the IVB group. The difference in mean CMT changes at 6 weeks and 12 weeks was significant among the groups in the subgroup ≥350 μm (P < 0.001 and P < 0.001) in favor of the IVB group and in the subgroup 250 μm to 349 μm at 24 weeks in favor of combined IVB/IVT group (P < 0.001).
Conclusion: In the primary treatment of diabetic macular edema, initial CMT may be an important factor in decision making. Regardless of initial CMT, IVB caused a better visual outcome only at 6 weeks. With longer follow-up, however, IVB was superior to IVB/IVT and macular laser photocoagulation only in the eyes with initial CMT of ≥350 μm. Concerning CMT reduction, this superiority of IVB in the eyes with initial CMT of ≥350 μm was not observed beyond 12 weeks.