effect of ranibizumab versus bevacizumab on the macular perfusion in diabetic macular edema

Conditions: Diabetic Macular Edema; Macular Ischemia; Diabetic Retinopathy; Vascular Endothelial Growth Factor Overexpression

Summary: the early treatment diabetic retinopathy study (etdrs) group founded guidelines for treating patients with clinically significant diabetic macular edema (dme) with focal/grid macular laser photocoagulation. since then, macular laser, and steroids, were the main therapies for the treatment of dme until anti-vascular endothelial growth factors (anti-vegf) drugs were developed after a growing body of scientific evidence implicated vegf in the pathophysiologic process of dme. anti-vegf drugs have been implicated in the treatment of dme. vegf has been shown to play an important role in the occurrence of increased vascular permeability in dme. vegf levels are significantly higher in patients with dme and extensive leakage than in patients with minimal leakage. many studies such as diabetic retinopathy clinical research \[drcr\] network studies, restore study, rise and ride research group, and the bolt study have supported the use of anti-vegf agents in the treatment of dme with better visual outcomes using anti-vegf injections alone or in combination with other treatments. several ocular complications of intravitreal anti-vegf injections have been reported including endophthalmitis, cataract, and retinal detachment. the different effects on macular perfusion between different anti-vegfs have yet to be fully concluded with mixed conclusions that it increases or decreases or has no effect on perfusion of the macula in response to anti-vegf treatment. in many of these studies, however, patients with more ischemic retinas were not included. retinal ischemia is a vital factor determining the diabetic retinopathy progression and prognosis. optical coherence tomography angiography (octa) detects blood flow by analyzing signal decorrelation between two sequential oct cross-sectional scans at the same location. as it detects the movements of red blood corpuscles within the vessels, compared to the stationary retinal surroundings, which will result in signal disparity and imaging the split-spectrum amplitude-decorrelation angiography (ssada) algorithm improves the signal to noise ratio. octa is considered a reliable tool in the detection and quantification of macular ischemia in diabetics. in this study, the investigators aim to compare the effect of repeated intravitreal injections of ranibizumab and bevacizumab on the perfusion of different capillary layers in the macula of diabetic patients using octa.

diabetic retinopathy is the major cause of blindness in developed but also in developing countries. the disruption of the blood-retinal barrier and the subsequent accumulation of fluid in the intraretinal layers result in diabetic macular edema (dme), the leading cause of central vision loss in these patients. the early treatment diabetic retinopathy study (etdrs) group founded guidelines for treating patients with clinically significant dme (csme) with focal/grid macular laser photocoagulation. since then, macular laser, and steroids, were the main therapies for treatment of dme until anti-vascular endothelial growth factors (anti-vegf) drugs were developed after a growing body of scientific evidence implicated vegf in the pathophysiologic process of dme. anti-vegf drugs have been implicated in the treatment of dme. vegf has been shown to play an important role in the occurrence of increased vascular permeability in dme. vegf levels are significantly higher in patients with dme and extensive leakage than in patients with minimal leakage. many studies such as diabetic retinopathy clinical research \[drcr\] network studies, restore study, rise and ride research group, and the bolt study have supported the use of anti-vegf agents in the treatment of dme with better visual outcomes using anti-vegf injections alone or in combination with other treatments. drcr network protocol t found statistically insignificant difference between ranibizumab and bevacizumab on visual acuity and central macular thickness in diabetic macular edema. several ocular complications of intravitreal anti-vegf injections have been reported including endophthalmitis, cataract, and retinal detachment. the different effects on macular perfusion between different anti-vegfs have yet to be fully concluded with mixed conclusions that it increases or decreases or has no effect on perfusion of macula in response to anti-vegf treatment.in many of these studies, however, patients with more ischemic retinas were not included. retinal ischemia is a vital factor determining the diabetic retinopathy progression and prognosis. using ocular ultrasound some studies showed retinal arteriolar vasoconstriction in eyes treated with anti-vegf, while others showed decreased blood flow velocities in all retro-bulbar arteries after intravitreal injection of anti-vegf. this may indicate that anti-vegf may have an effect on ocular perfusion. fluorescein angiography (fa) was the method used to assess changes in macular perfusion after anti-vegf injections in most of the studies. despite its clinical value, however, fa is known to have documented risks. optical coherence tomography angiography (octa) is an excellent non-invasive modality to acquire high-resolution images of the retinal vasculature that can be utilized in the treatment of retinal disease without the need for dye injection. it allows the visualization of both the superficial and deep retinal capillary layers separately and the construction of microvascular flow maps. octa detects blood flow by analyzing signal decorrelation between two sequential oct cross-sectional scans at the same location. as it detects the movements of red blood corpuscles within the vessels, compared to the stationary retinal surroundings, which will result in signal disparity and imaging the split-spectrum amplitude-decorrelation angiography (ssada) algorithm improves the signal to noise ratio. octa is considered a reliable tool in the detection and quantification of macular ischemia in diabetics. in this study, the investigators aim to compare the effect of repeated intravitreal injections of ranibizumab and bevacizumab on the perfusion of different capillary layers in the macula of diabetic patients using octa.

Eligibility criteria:
inclusion criteria: 1. patients ≥18 years old with type 1 or 2 diabetes mellitus with decreased bcva due to center involving diabetic macular edema on spectral-domain optical coherence tomography. 2. patients with central macular thickness "cmt" of ≥ 300 micrometers exclusion criteria: 1. ocular conditions that may affect macular perfusion (e.g. retinal vascular diseases, uveitis, vasculitis etc.) 2. history of vitreo-retinal surgeries. 3. previous macular laser treatment 4. presence of epi-retinal membrane involving the macula or vitreo-macular traction. 5. media opacity preventing good image quality. 6. uncontrolled glaucoma. 7. thrombo-embolic events within 6 months 8. previous intravitreal injections of anti-vegf

Keywords: diabetic macular edema macular perfusion optical coherence tomography angiography anti-vegf