Comparative Study between Triamcinolone and Bevacizumab Effect on Choroidal Thickness in Diffuse Diabetic Macular Edema by Optical Coherence Tomography

Abstract

SUMMARY D iabetic retinopathy is due to the breakdown of retinal vasculature integrity and hemodynamic abnormalities. Studies of Doppler flowmetry indicated that the choroidal blood flow may decrease in the early stage of diabetic retinopathy, and decrease further in the presence of macular edema. Similarly, histologic studies suggested that diabetic retinopathy may cause atrophy of the choriocapillaris endothelium. The choroidal vasculature, especially the choriocapillaris, provides oxygen and nutrients to the outer retina and is responsible for maintaining the highly metabolically active photoreceptor cells. Since there is no retinal vasculature in the foveal region, impairment of the choriocapillaris may cause severe functional damage to the retinal tissue in the fovea. Therefore, in vivo evaluation of the structural changes in the choroid might be very insightful to determine the pathogenesis of progression of the macular changes in diabetic eyes. There are few clinical studies on choroidal angiopathy in diabetes. This is because of the difficulty of imaging the choroid in vivo. Imaging the choroid with conventional commercial SD-OCT has been difficult, mainly because of difficulty in signal transmission beyond the retinal pigment epithe¬lium. However, the recent introduction of a novel technique for choroidal imaging, enhanced depth imaging technique by OCT, by Spaide et al provides in vivo cross-sectional visualization of deeper choroidal layers. It was reported that choroidal circulation is affected by diabetic diffuse macular edema. This study compared the effect of IVTA, PSTA and IVB on the subfoveal choroidal thickness in patients with diffuse diabetic macular edema more than 400µ by EDI technique. This study included 30 eyes of 24 diabetic retinopathy patients (51-75 years old), type 2 DM with diffuse DME > 400µ, 14 females and 10 males were randomized into three groups with 10 eyes in each group as following: IVTA (group I), IVB (group II) and STA (group III). Follow up is done by assessment of BCVA, CMT, SFCT and IOP 2 and 4 weeks after injection. Subfoveal choroidal thickness was thinner in eyes with DME (245.9±74.7 μm) when compared to normative data (272±81 μm). The baseline value of the mean SFCT (mean ±SD) was 257.2 ± 84.0µ in group I (IVTA), 271.1 ± 68.6 µ in group II(IVB) and 209.6 ± 62.4 µin group III(STA) showed no statistically significant change after 4 weeks of treatment to 237.6 ± 84.0 µ, 250.1 ± 66.9µ, 211.3 ± 59.1µ in group I, II and III respectively. The mean CMT was 505.2 ±142.7 µm, 435.4± 39.5 µm, and 494.4 ±145.2µm in group I(IVTA), II (IVB)and III(STA) respectively which decreased significantly to 362.9 ± 53.2µ, 375.6 ±61.5 µ, 471.2± 147.1µ respectively. The mean baseline BCVA was 0.85 ±0.2 logMAR units in the IVTA group, 0.86±0.4 logMAR units in the IVB group and 0.79±0.2 logMAR units in the STA group which significantly improved in group I (IVTA) to 0.49± 0.1 logMAR units with no significant improvement in group II (IVB) to 0.64 ± 0.4 logMAR units and no significant improvement in group III (STA) to 0.71 ± 0.2 log MAR units. No significant correlation is found between the SFCT and the macular thickness in each group before and after treatment.