| Background:Type 2 diabetes is heterogeneous group of metabolic disorder characterized by chronic hyperglycemia and represents a significant health problem. Interaction between a genetic predisposition and behavioral and environmental risk factors leads to type 2 diabetes.Diabetic Retinopathy (DR) is severe and wide spreading diseases. The presence of diabetic retinopathy is evidenced by the appearance of retinal micro vascular lesions. Early changes include microaneurysms, hemorrhages, hard exudates, cotton wool spots, intraretinal microvascular abnormalities and venous bleeding, which is the characteristics of nonproliferative diabetic retinopathy (NPDR). The more severe state of proliferative diabetic retinopathy (PDR) is marked by the formation of abnormal fragile new blood vessels that are prone to hemorrhage (neovascularization). Diabetic macular edema is a major cause of blindness in diabetic retinopathy and macular ischemia is an important mechanism. Diabetic macular ischemia can predict the development and prognosis of diabetic retinopathy,so it is a key point to observe the macular ischemia in patients with diabetes mellitus. Fundus fluorescein angiography can be used in patients with macular ischemia, but cannot be completely quantitative,and because it is invasive examination,and there will be a small amount of serious complications. Optical Coherence Tomographic Angiography (OCT-A) is a noninvasive technique that provides high resolution images of the retina. Useful details of vascular layers can be extracted using OCT angiography. OCT-A can be used to distinguish the blood flow signal of retinal signal by the method of correlation or phase difference, so as to construct the retinal microvascular network.Objective:To compare optical coherence tomography (OCT) angiographic parameters in retina and choriocapillary between Normal subjects and diabetic patients without diabetic retinopathy (No DR) and between diabetic patients without diabetic retinopathy and diabetic patients with retinopathy (with DR). Correlate FAZ area with visual acuity of diabetic patients.Methods:It is a cross-section study. Data were collected from Diabetic retinopathy clinic,Ophthalmology department, First affiliated hospital, Yunnan, China. Total 79 patients were included in the study (147 eyes), out of which 23 were normal subjects, 46 eyes (31.29 %),27 patients were with No DR, 52 eyes (35.37 %) and 29 patients were with diabetic retinopathy were 49 eyes (33.33 %). The age, gender, history of diabetes, hypertension were noted. Investigations were done Intraocular pressure (IOP), Fundus Photography, Best corrected Visual Acuity (BCVA). Slit lamp examination were done using direct and/or indirect ophthalmoscope to all the patients. All the subjects were examined by optical coherence tomography angiography (OCT-A), and the macular blood flow density map was obtained at 3 levels in the range of 3 x 3mm. Optical coherence topography angiographic parameters were as follows: en face OCT image was segmented in vessel density (%) ( in superficial retinal vessel network, deep retinal vessel network and in choriocapillary vessel network), foveal avascular zone (FAZ) area (mm2) in superficial retinal vessel network of parafovea and retinal layer density (?m) were taken.Result:Part 1: Comparison between Normal patient and patient with No Diabetic retinopathy (No DR).The mean (standard deviation) of age of Normal subject and patients with No Diabetic retinopathy was found to be 46.43 (±9.10) years and 59.22 (±11.01) years respectively, P=4.421. The total 13 male ( 56.52%) and 10 female (43.48 %) were present in normal group and 19 male (70.37 %) and 8 female (29.63 %) in patient with No DR (P =0.30). The mean(SD) of IOP of normal subjects and patients with No DR was 13.41 (±1.68) mmHg and 13.96(±2.05) mmHg respectively, P= 0.14. logMAR visual acuity, mean (SD) of normal was 0.05(± 0.05) logMAR and BCVA logMAR, mean (SD) of diabetic patient with no DR was 0.09(±0.11) logMAR, P = 0.02. Retinal thickness [internal limiting membrane (?m) to retinal pigment epithelium (?m) (ILM - RPE)] in the parafoveal region were compared between normal patients (317.73 ± 14.32?m) and patients with No DR (310.69 ±22.37?m), there was no significant difference (P = 0.063, >0.05) of retinal thickness between these two groups.The parafoveal vessel density decreased in patient with No DR when compared with normal subject,Superficial retinal vessel network of patient with No DR ( 49.20 ± 4.73 %) and normal subject (51 .66 ± 3.21 %,P = 0.0033),deep retina vessel network of patient with No DR (55.69 ±4.50 %) and normal subject (58.64 ± 3.02 %, P = 0.00022) and choriocapillary vessel network of patient with No DR (64.04 ±2.31 %) and normal subject (64.88 ± 1.70 %,P=0.042). Foveal avascular zone in superficial retina of No DR patients ( 0.53± 0.68mm2)was greater than in normal group (0.37 ± 0.08 mm2, P = 0.04).Part 2: Comparison between patients with Diabetes mellitus (patients with No DR and patient with DR).The mean (SD) of age of patients with No DR and patients with DR is 59.22 (±11.01)years and 58.5 (±13.44) years respectively, P= 0.82. Total number of male and female presented with type 2 Diabetes mellitus but No Diabetic retinopathy were 19 (70.37 %) and 8(29.63 %) respectively and total number of male and female presented with Diabetic retinopathy were 18 (62.07 %) and 11 (37.93 %) respectively ( P=0.51). The mean .(SD) of duration of diabetes mellitus in patients with No DR patients and patients with DR is 8.32(±7.92) years and 10.63 (±8.28) years respectively, P= 0.28. The mean (SD) of IOP of patients with No DR and patients with DR is 13.96 (±2.05) mmHg and 14.71 (±2.50) mmHg respectively, P= 0.10. BCVA logMAR, mean (SD) of diabetic patient with no DR was 0.09(± 0.11) logMAR and BCVA logMAR, mean (SD) of Diabetic patient with DR was 0.32 (±0.39) logMAR,P = 0.0002.No significant difference was found in retinal thickness (ILM - RPE) between patients with No DR (310.69 ± 22.37?m) and patients with DR (308.10 ± 25.64?m),P= 0.59. The parafoveal vessel density decreased in patient with No DR when compared with patient with DR,Superficial retinal vessel network of patient with DR (46.81 ± 5.44 %) and patient with No DR (49.20 ± 4.733 %,P = 0.02),deep retina vessel network of patient with DR (52.34 ±6.71 %) and patient with No DR (55.69 ±4.50 % , P = 0.004) and choriocapillary vessel network of patient with DR (62.87 ± 3.22 %) and patient with No DR (64.04 ± 2.31 %,P =0.04). Foveal avascular zone in superficial retina vessel network of patients with DR (0.55 ±0.49 mm2) was greater than in patient with No DR ( 0.53± 0.68mm2),but statically could not be proven (P =0.44).Part 3: Diabetic patients correlation between their SFAZ and visual acuity.The correlation between superficial FAZ (mm2) was done with patients' visual acuity(logMAR) in patient with No DR, r =0.34, P = 0.01, correlated positively. Similarly, in patients with DR, the correlation between superficial FAZ (mm2) was done with patients'visual acuity (logMAR), r= 0.39, P = 0.005, correlated positively.Conclusion:Superficial retinal vessel density,deep retinal vessel density and choriocapillary vessel density in parafoveal reason significantly decreased in patients with type 2 diabetes mellitus without Diabetic Retinopathy. The Superficial foveal avascular zone increases in the patient with type 2 diabetes mellitus. No influence of age, gender, IOP and duration of diabetes were found in between different groups. Optical coherence topographic angiography is a novel imaging modal to quantify the retinal capillary microvasculature in patients with diabetes. |
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