Study On Hemodynamic Changes Of Retrobulbar Artery In Diabetic Patients By Color Doppler

ObjectiveTo measure and investigate changes of blood flow velocity by Color Doppler Flow Imaging (CDFI) in the central retinal artery (CRA) and short posterior ciliary artery (PCAs) in diabetic retinopathy (DR) and to compare the results with those in healthy control subjects. We also investigated whether the changes of blood flow velocity in the CRA and PCAs are significant with respect to the different stages of DR progression. We hope CDFI can be a useful method to monitor the progression of DR and could therefore help in deciding on the right time to begin or continue DR therapy.Methods58 diabetic patients with different stages of DR from Department of Endocrinology, Nanfang Hospital, Guangzhou, were prospectively included in this investigation. Diabetes mellitus was diagnosed on the basis of clinical presentation and features according to WHO standard issued in 1999. Baseline examinations included variables such as age, sex, blood pressure, a history of past and present systemic and ocular medication, a systemic and ocular history. An eye examination included determination of visual acuity, refraction, a slit lamp examination, funduscopy. Following ophthalmoscopy or fluorescence fundus angiography(FFA), DR was classified into 5 grades according to Clinical Classification Standard of Diabetic Retinopathy issued by the Chinese Ophthalmological Association. Patients were excluded from this study if they demonstrated a history of serious systemic cardiovascular or other systemic disease, previous ocular surgery, ocular trauma, laser photocoagulation, glaucoma or uveitis, evidence of retinal arterial or vein occlusion, ischemic optical neuropathy, macular degeneration or any ocular medication to the study eye. On the day of the examination the plasma glucose and glycated hemoglobin (HbA1 c ) level were detected.In this investigation we included also 30 healthy age- and sex-matched subjects recruited from the hospital staff and inpatents to form the health control groups(HC group). They were without any systemic disease or ocular pathology, systemic or ocular medication. At the time of inclusion and on the day of the examination systolic and diastolic blood pressure, intraocular pressure and plasma glucose level were detected. Ocular blood flow velocity was determined by CDI of CRA and PCAS using the Sequioa 512 by Siemens with a 8L15 (multifrequency 8-15 MHz) transducer. After the procedure had been explained to the subjects they assumed a supine position and the probe was applied to the closed eyelids using sterile coupling gel. Angle correction was applied to the pulsed Doppler recordings to minimize errors in the measured velocities. With CDFI we measured the peak systolic velocity (PSV, cm/s), end-diastolic velocity (EDV, cm/s) and resistant index of blood flow in the CRA and PCAS. In all cases only the right eye of each patient was included in the study. In the statistical analysis we included 58 eyes of 58 diabetic patients with different stages of DR. To find out whether the changes of blood flow velocity in CRA and PCAS are significant considering the different stages of DR progression, we divided the 58 eyes of 58 diabetic patients into three groups: NDR(27eyes without DR), NPDR(non-proliferative DR, 14 eyes with DR classified to grade 1 to 3) and PDR(proliferative DR, 17 eyes with DR classified to grade 4 or 5) groups.Statistical analysis comparing the results of groups NPDR, NPDR, PDR and HC was carried out. We used the statistical program SPSS (version 10.0 for Windows). A one-way analysis of variance (ANOVA) across the three groups was carried out for each set of variables followed where appropriate by a t test using the Bonferroni correction. Statistical significance was set at P＜0.05.Results There was no statistically significant difference in the age and sex of the subjects (ANOVA, P＜0.05) among the four groups.Statistical analysis (ANOVA) indicated differences in the PSV, EDV and RI in the CRA between the four groups (p＜0.05). Follow-up t test with Bonferroni correction showed a statistically significant decrease in PSV in groups NPDR and SNPDR/PDR compared with group HC (p＜0.05), but comparison of group NPDR with PDR yielded no statistically significant difference (p＞0.05) in PSV in the CRA. Follow-up t test with Bonferroni correction showed a statistically significant decrease in EDV in group DR compared with group HC (p＜0.01), but comparison of group NDR with group HC revealed a statistically difference (p＜0.05) in EDV in the CRA.Statistical analysis (ANOVA) indicated significant differences in the EDV and RI in PCAs between the four groups (p＜0.05), but there was no statistically significant difference in the PSV (p＞0.05) between NDR and NPDR groups. Follow-up t test with Bonferroni correction showed a statistically significant decrease in EDV in group NPDR/PDR compared with group HC (p＜0.05) and a statistically significant increase in the RI in group NPDR compared with group PDR and in group NPDR versus group NDR (p＜0.05).Our research showed that duration of diabetics are positively corelated with RI of CRA and PCAs and GHb also has positive correlation with RI of CRA and PCAs.Multi-variant analysis through component matrix showed that there are 3 dominant components. Among them, component C1 which stands for hemodynamic related CRA and PCAs indices, course, FBG, GHb, systolic and diastolic blood pressure, had the highest OR value. Logistic regression indicated that CRA-RI are most closely related to the pathologic progression of DR.ConclusionVascular changes and consequently ocular hemodynamic changes play the central role in the pathogenesis of DR. The exact nature of ocular blood flow abnormalities in the different stages of DR is still a matter of controversy. In the literature conflicting evidence exists as to whether ocular blood flow is increased or decreased in DR. This is a consequence of the variety of techniques used to assess the changes of ocular hemodynamics in DR.In the present investigation we assess the changes of ocular hemodynamics in DR with Doppler. The results of our investigation indicated a significant decrease in PSV and EDV in the CRA of diabetics with DR compared to healthy controls. The decrease in PSV and EDV in the CRA correlates with the progression of DR. Meanwhile, from the changes of velocity and RI in PCAs, it can be indicated that hemodynamic changes of choriod circulation also existed and is as significant as that in CRA. The result don't agree with that of NieFang etc, who found that PSV in PCAs decreased significantly but EDV and RI showed no significant changes.It has been estimated that of the total ocular blood supply less than 10% flows to the retina; the remainder is directed to the choroid via the ciliary circulation. The outer retinal layers, including the high metabolic complex of retinal pigment epithelium/photoreceptors, are supplied by the choroid. Diabetes mellitus-associated vascular damage to choroidal circulation is jet not fully understood, but recent evidence suggests that choroidal angiopathy may also occur in diabetics. The concept of diabetic choroidopathy was first suggested by Hidayat and Fine, who observed capillary dropout, basement membrane thickening and choroidal neovascularization in eyes with advanced diabetes mellitus. McLeod and Lutty reported choriocapillaris dropout in subjects with diabetes mellitus that in some cases seemed to be associated with choroidal neovascularization. In our investigation we found a significant decrease in EDV in the PCAS of diabetics with severe nonproliferative or proliferative DR compared to healthy controls. It is known that a decrease in EDV points to the presence of an increase in distal vascular resistance. We also found a significant increase of RI in the PCAS of diabetics with proliferative DR compared to diabetics with mild and moderate nonproliferative DR or compared to healthy controls. The RI increases when there is an increase in distal vascular resistance. Our results of a decrease in EDV and an increase in RI in the PCAS of diabetics with advanced DR confirm the concept of diabetic choroidopathy.In conclusion, in this investigation Doppler was used to determine significant changes of blood flow velocity in the CRA and PCAS in DR compared with healthy control subjects; changes in blood flow velocity gain in significance considering the progression of DR. This points to the presence of circulatory changes in the CRA and PCAs in diabetic patients with DR. We believe that Doppler can be a useful additional method to monitor the progression of DR and could therefore help in deciding on the right time to begin or continue DR therapy.