| Part 1-The Influence of Age and Central Foveal Thickness on Foveal Zone Size in Healthy PeopleOBJECTIVE:To investigate the influence of age and central foveal thickness (CFT) on the foveal avascular zone (FAZ) size in healthy people using optical coherence tomography angiography (OCTA).METHODS:A cross-section study. One hundred thirty-two healthy subjects (224 eyes) were included. All participants underwent examination with OCTA. CFT and FAZ size, including vertical radius (VR), horizontal radius (HR), and area, were measured.RESULTS:Linear regression analysis showed a positive correlation between age and FAZ size. The HR, VR, and area had an increase of 0.001 mm (P=0.002),0.001 mm (P=0.001), and 0.001 mm2 (P=0.000) each year, respectively. There was a negative correlation between CFT and FAZ size. When the CFT increased per 1 pm, the HR, VR, and area decreased by 0.002 mm (P=0.000),0.001 mm (P=0.000), and 0.003 mm (P=0.000), respectively.CONCLUSIONS:FAZ size increases with age and de- creases with CFT. OCTA is a novel method to study the FAZ in healthy people.Part 2-A morphological study of the foveal avascular zone in patients with diabetes mellitusPURPOSE:To investigate the area and radius of the foveal avascular zone (FAZ) in patients with diabetes mellitus (DM) using optical coherence tomography (OCT) angiography.METHODS:Sixty-five patients with DM (113 eyes) and 62 healthy controls (85 eyes) were included in the study. All of the participants underwent examination with OCT angiography. The vertical radius (VR), horizontal radius (HR) and area of the FAZ were measured.RESULTS:The differences in HR, VR and area between the control and DM groups were statistically significant (p=0.01,0.00 and 0.00, respectively). There were no statistically significant differences between the control group and the no- diabetic retinopathy (DR) group in HR or VR (p=0.07 and 0.08, respectively), but there was a statistically significant difference in area (p=0.04). The size of the FAZ was greater in patients with DR compared to the control group. The differences in HR, VR and area were statistically significant (p= 0.01,0.00 and 0.00, respectively). In addition, the clinically significant macular oedema (CSME) group also had a larger FAZ area than the non-CSME group (p=0.02).CONCLUSIONS:Patients with DM had a larger FAZ, and patients with more severely damaged retinas had a much larger FAZ. OCT angiography is a new convenient and noninvasive meth- od for studying the FAZ. This novel examination will yield considerable amounts of data that cannot be obtained using previous research methods.Part 3-The analysis of the macular vascular density in healthy people and diabetic patientsPURPOSE:To investigate the macular vascular density in patients with diabetes mellitus (DM) using optical coherence tomography (OCT) angiography.METHODS:Five-three patients with 2 type DM (98 eyes) and 60 healthy controls (98 eyes) were included in the study. All of the participants underwent examination with OCT angiography, and the macular vascular density maps (including superficial layer, deep layer, outer retina layer and choroid cap layer) were got from the examination. The DR patients were divided into no-DR, NPDR and PDR group, according to the the modified Early Treatment Diabetic Retinopathy Study (ETDRS) retinopathy severity scale.RESULTS:Sixty healthy subjects (14 men,46 women) served as the control group. Subjects’ ages ranged from 37 to 78 years (54.58±11.12 years). The DM group comprised 53 patients (19 men,34 women), the ages ranged from 32 to 80 years (57.34±10.65 years). The age did not have statistically significant differences between the control group and DM group (p=0.183). In the DM group, the macular vascular density of the 4 layers (superficial layer, deep layer, outer retina layer and choroid cap layer) is 0.4956±0.0386, 0.5373±0.0376,0.3971±0.0373 and 0.6533±0.0227 respectively. And in the control group, they were 0.5281±0.0294,0.5726±0.0240,0.3884±0.0395,0.6659±0.0123 respectively. The differences in superficial, deep retina and choroid cap layer between the control and DM groups were statistically significant (p=0.000,0.000 and 0.000, respectively). But the difference in outer retina layer was not (p=0.112). It was clear that the macular vascular density decreased with the stage of diabetic retinopathy increasing. In superficial retina and deep retina layers, macular vascular density of healthy people increases by about 1% every year, but it decreases by about 1% every year in outer retina layer. In choroid cap layer, the value is stable.CONCLUSIONS:The macular vascular density in DM patients decreases clearer compared to healthy people. The OCT angiography is a reliable tool to show the value of the macular vascular density.
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