To investigate the effects of intravitreal bevacizumab injection on diabetic macular edema (DME) of different types classified using Optical Coherence Tomography (OCT).

A total of 82 eyes with refractory DME were enrolled. The DME was classified into diffuse, cystoid, or serous type based on the OCT findings. All cases had received an intravitreal injection of 1.25 mg bevacizumab each month for three months. Foveal thickness, macular volume, and best corrected visual acuity (BCVA) were measured before and one month after the injection, and the interval changes in these parameters were compared.

The types of DME were classified as follows: diffuse macular edema 50%, cystoid macular edema 31.7%, and serous macular detachment 18.3%. Foveal thickness and total macular volume after intravitreal bevacizumab injection decreased in all types, and the cystoid and serous types showed better response than did the diffuse type with regard to foveal thickness. However, there were no significant differences in the extent of the change in total macular volume or BCVA among the three types of DME.

There were differences in the therapeutic effects of intravitreal bevacizumab injection among the different types of DME classified using OCT. These differences may be associated with the stabilizing effect of the bevacizumab. This effect was stronger with regard to vascular permeability, the primary factor in the pathogenesis of the cystic and serous types, than with regard to leakage from the microaneurysm, the primary factor in the pathogenesis of the diffuse type. Practical application of bevacizumab to eyes with different DME types will help in further evaluating intravitreal bevacizumab injection as a treatment option for DME.