Faryan Tayyari

Variability and repeatability of quantitative, Fourier-domain optical coherence tomography Doppler blood flow in young and elderly healthy subjects.

PURPOSE The purpose of this study was to determine the within-session variability and between-session repeatability of spectral Fourier-domain optical coherence tomography (Doppler FD-OCT) Doppler retinal blood flow measurements in young and elderly subjects. METHODS Doppler FD-OCT blood flow was measured using the RTVue system. One eye of each of 20 healthy young (24.7 ± 2.7 years) and 16 healthy elderly (64.6 ± 5.1 years) subjects was randomly selected, and the pupil was dilated. The double circular scanning pattern of the RTVue was employed. Six Doppler FD-OCT measurements (i.e., each separate measurement comprising an upper and a lower nasal pupil scan) were acquired at each session. Measurements were repeated approximately 2 weeks later. Total retinal blood flow was calculated by summing flow from all detectable venules surrounding the optic nerve head. The coefficient of variation (COV) and coefficient of repeatability (COR) were calculated for each individual. RESULTS The individual COVs for retinal blood flow for young subjects ranged from 0.4% to 20.4% (median 7.5%) and for the elderly subjects ranged from 0.6% to 34.6% (median 9.2%). The group mean CORs for retinal blood flow for young participants were 6.4 μL/min (median 5.91 μL/min, relative to a mean effect 39.8 μL/min) and for elderly subjects were 10.5 μL/min (median 9.2 μL/min, relative to a mean effect 46.4 μL/min). CONCLUSIONS Doppler FD-OCT gave consistent and repeatable blood flow measurements within retinal venules in normal subjects. Considering the individual variation in blood flow measurements, confidence limits for retinal hemodynamics need to be determined on an individual basis.

Grader learning effect and reproducibility of Doppler Spectral-Domain Optical Coherence Tomography derived retinal blood flow measurements

To investigate grader learning effect and to quantify intergrader reproducibility of Doppler Spectral‐Domain Optical Coherence Tomography (SD‐OCT) derived retinal blood flow measurements.

Retinal Oxygen Saturation in Patients with Primary Open-angle Glaucoma Using a Non-flash Hypespectral Camera

ABSTRACT Purpose/Aim: To investigate retinal vessel blood oxygen saturation in patients with primary open-angle glaucoma (POAG) and healthy controls.Materials and Methods: A novel non-flash hyperspectral retinal camera was used to image 17 healthy individuals (mean age 69.3 ± 6.1 years) and 22 patients with stable POAG (mean age 69.2 ± 5.8 years) at 548, 569, 586, 600, 605, and 610 nm wavelengths. POAG patients were grouped as mild–moderate (n = 13) and moderate–severe (n = 9) based on Humphrey 24-2 visual field results (mean deviation [MD] < −6 and MD ≥ −6; respectively). Optical density values were extracted using Image-J software for blood oxygen saturation (SO2) determination. Arteriolar and venular SO2 were measured within 1.5 optic nerve head diameters from the disc margin along the vessels in the inferior temporal quadrant of the tested eye per subject. Analysis of variance (ANOVA), student t-test, and Pearson’s correlation were used for statistical analysis of the data (p < 0.05). Results: Venular, arteriolar, and arteriovenous (AV) differences in SO2 measurements were not significantly different between controls and the combined POAG groups (p > 0.06 for all). However, mean venular SO2 was significantly higher in the POAG with MD ≥ −6 dB when compared to controls and patients with mild glaucoma (p = 0.005). The AV differences were significantly lower in patients with more severe field defect (p = 0.006) compared to the remaining groups. No differences were found in the mean arteriolar SO2 between the groups (p = 0.155). Significant correlations were found only between higher visual field MD values and higher venular SO2 (p = 0.048) but not the remaining SO2 measurements. Conclusion: Patients with POAG and moderate–severe visual field defect had higher venular SO2 compared to those with mild–moderate defect and controls. This would indicate reduced oxygen consumption in more advanced glaucoma likely as a result of ganglion cell degeneration.

Aqueous humour concentrations of TGF-β, PLGF and FGF-1 and total retinal blood flow in patients with early non-proliferative diabetic retinopathy

To correlate angiogenic cytokines in the aqueous humour with total retinal blood flow in subjects with type 2 diabetes with non‐proliferative diabetic retinopathy (NPDR).

Aqueous humor endothelin-1 and total retinal blood flow in patients with non-proliferative diabetic retinopathy

PurposeThe purpose of this study was to determine the association between aqueous ET-1 levels and total retinal blood flow (TRBF) in patients with non-insulin-dependent type 2 diabetes mellitus (T2DM) and early non-proliferative diabetic retinopathy (NPDR).Patients and methodsA total of 15 age-matched controls and 15 T2DM patients with NPDR were recruited into the study. Aqueous humor (~80–120 μl) was collected before cataract surgery to measure the levels of ET-1 using suspension multiplex array technology. Four weeks post surgery, six images were acquired to assess TRBF using the prototype RTVue Doppler FD-OCT (Optovue, Inc., Fremont, CA, USA) with a double circular scan protocol. At the same visit, forearm blood was collected to determine plasma glycosylated hemoglobin (A1c) levels.ResultsAqueous ET-1 was significantly elevated in the NPDR group compared with the control group (3.5±1.8 vs 2.2±0.8, P=0.02). TRBF was found to be significantly reduced in the NPDR group compared with the control group (34.5±9.1 vs 44.1±4.6 μl/min, P=0.002). TRBF and aqueous ET-1 were not correlated within the NPDR group (r=−0.24, P=0.22). In a multivariate analysis, high A1c was associated with reduced TRBF and aqueous ET-1 levels across control and NPDR groups (P<0.01).ConclusionAqueous ET-1 levels were increased while TRBF was reduced in patients with NPDR compared with the control group. Although not directly associated, the vasoconstrictory effects of ET-1 are consistent with a reduced TRBF observed in early DR. ET-1 dysregulation may contribute to a reduction in retinal blood flow during early DR.