Evaluation of ischemia risk in retinal vein occlusion with optical coherence tomography angiography

PURPOSE: To detect the preliminary signs of ischemia by looking at the vessel density (VD) values of the deep capillary plexus (DCP) and superficial capillary plexus (SCP) layers of patients who have undergone branch retinal vein occlusion (BRVO) with the optical coherence tomography angiography (OCT-A) device. MATERIALS AND METHODS: In our study, OCT-A images of affected eyes of 30 patients with BRVO were examined at the first visit, 3rd, 6th and 9th months. OCT-A images of the healthy eyes of the same patient group were taken as the control group. In our study, the SCP and DCP VD values of the affected eye were compared with the unaffected healthy eye and among themself between controls. In addition, the correlation of OCT central subfield thickness (CST) value, OCT-A central quadrant VD and visual acuity (VA) was also made. RESULTS: In this study, no significant change was observed in the SCP layer in the parafoveal quadrants of the affected eye except the central quadrant compared to the healthy eye. The first control central quadrant SCP-VD was higher than the following controls (p<0.001). When we look at the DCP layer, there was an increase in the central quadrant VD (p<0.001) and a decrease in the superior quadrant VD (p<0.025) in the affected eye compared to the healthy eye. When we separate the patient group into inferior and superior arcuate vein occlusion, no significant change was detected in the SCP layer except the central quadrant, while in DCP, there was an increase in the central quadrant VD value and a decrease in the VD of the affected quadrant. In the correlation analysis, the OCT-A central quadrant SCP-VD value was positively correlated with OCT-CST for 9 months (p ≤ 0.01). In the DCP layer, a positive correlation was observed in the 3rd and 6th months (p ≤ 0.01). A negative correlation was observed between VA and SCP central quadrant VD value in the 3rd and 6th months, and in the DCP layer at first presentation and 3 months (p ≤ 0.01). The correlation of VA with OCT-CST was always positive throughout the 9 months (p ≤ 0.01) CONCLUSION: In the SCP layer, except for the increase in VD in the central quadrant, no significant change was observed in other quadrants. The VD of the DCP layer remained lower in the affected quadrant compared to the healthy eye for 9 months. From here, we can conclude that the DKP layer is more sensitive to ischemia. When we look at the correlation of VA with the central quadrant VD, this correlation was seen more clearly in the DCP layer. In the first months, a negative correlation is observed due to macular edema, and after the edema is removed, this correlation disappears because the loss in VD is more clearly selected by the device. The insufficient number of patients and the absence of BRVO cases in the ischemic form are among the limitations of the study. Therefore, additional studies are needed to know how VD will be affected in the long term in the ischemic form.