Measurement of total blood flow in the normal human retina using Doppler Fourier-domain optical coherence tomography

Abstract

Aim-To measure total retinal blood flow in normal human eyes using Doppler Fourier-domain optical coherence tomography (FD-OCT).Methods-10 normal people aged 35 to 69 years were measured for the right eye using Doppler FD-OCT. Double circular scans around the optic nerve heads were used. Four pairs of circular scans that transected all retinal branch vessels were completed in 2 s. Total retinal blood flow was obtained by summing the flows in the branch veins. Measurements from the eight scans were averaged. Veins with diameters >33 μm were taken into account.Results-Total retinal blood flow could be measured in eight of 10 subjects: mean (SD) = 45.6 (3.8) μl/min (range 40.8 to 52.9 μl/min). The coefficient of variation for repeated measurements was 10.5%. Measured vein diameters ranged from 33.3 to 155.4 μm. The averaged flow speed was 19.3 (2.9) mm/s, which did not correlate with vessel diameter. There was no significant difference between flows in the superior and inferior retinal hemispheres.Conclusions-Double circular scanning using Doppler FD-OCT is a rapid and reproducible method to measure total retinal blood flow. These flow values are within the range previously established by laser Doppler flowmetry.Many of the leading causes of blindness are related to abnormalities in retinal blood flow, such as diabetic retinopathy and age-related macular degeneration. 1 2 Central and branch retinal vein occlusions are also common retinal diseases that are characterised by decreased retinal blood flow. In glaucoma, poor circulation in the retina and optic nerve is thought to be a risk factor for disease progression. 3 4 A practical and accurate method for retinal blood-flow measurement may be useful in the diagnosis and management of these diseases.Optical coherence tomography (OCT) 5 provides high-resolution cross-sectional imaging and is commonly used in the diagnosis and management of retinal diseases. 6 7 In addition to obtaining morphological images, OCT can also detect the Doppler shift of reflected light, which provides information on blood flow. 8 9 For Doppler Fourier-domain optical coherence tomography (FD-OCT), 10 11 light reflected by moving blood induces a Doppler frequency shift that is proportional to the velocity component parallel to the axis of the probe beam. This MATERIALS AND METHODS Study populationThe research protocol was approved by the institutional review board of the University of Southern California (USC), in accordance with the tenets of the Declaration of Helsinki. Ten healthy human subjects (four male, six female) between the ages of 35 and 69 years (average 57.4 years) participated in the study at the USC Doheny Eye Institute. Written informed consent was obtained from each subject. The right eyes were measured. The following inclusion criteria were met for these normal subjects: (a) no history or evidence of retinal pathology or glaucoma; (b) no history of keratorefractive surgery; (c) normal Humphrey SITA 24-2 visual field: a mean deviation (MD) and pattern standard deviat...

Optic nerve head perfusion in normal eyes and eyes with glaucoma using optical coherence tomography-based microangiography

“…Based on this concept, OMAG generates ONH microcirculatory information by subtracting two consecutive B-scans; the OCT signals from static retinal tissues are removed while the signals from moving blood cells remain. We have found OMAG has high intra-and inter-observer repeatability and reproducibility [coefficient of variation <3.7% (intra-observer) and intraclass correlation coefficient ≥0.953 (inter-observer); unpublished data], which compares favorably to traditional methods, such as DOCT (17). By averaging differences of each repetition, OMAG further enhances the signal-to-noise ratio and generates blood flow signals with better contrast.…”

Imaging chorioretinal vascular disease

“…Prototype Doppler OCT systems allow measurement of retinal blood flow by the assessment of light reflectivity changes in retinal blood vessels over short time periods. 37 'Swept-source' OCT systems allow significant increases in imaging sensitivity and speed (eg 4300 000 A-scans per second), through the use of a tunable laser, 38 whereas polarization-sensitive OCT may prove to encode much of the information provided by FAF. 39 Finally, the use of adaptive optics in OCT devices may increase the transverse resolution of OCT systems and provide cellular level detail.…”

Doppler Optical Coherence Tomography of Retinal Circulation

“…2 graders used the semi-automated DOCTORC software and 1 used an earlier totally manual software employed in previous publications. 2,3 The total retinal blood flows ( Table 1) determined by the two graders using DOCTORC software are similar to one another and to flow rates determined by the other grader using the manual software. Only 65% of the eyes had valid results because some of the data were not based on dual angle protocol, but single angle protocol.…”

“…13,14 Doppler OCT measurements made with the newer semi-automated DOCTORC software agreed closely with the results of manual measurements that we published previously. [1][2][3][4][5] The difference between DOCTORC measurements and manual measurements in individual cases, as measured by CV, is similar to inter-grader differences. This indicates that the difference was primarily associated with subjective portion of the grading process, and not the difference between software.…”