Pilot study of optical coherence tomography measurement of retinal blood flow in retinal and optic nerve diseases

Abstract

Purpose: To investigate blood flow changes in retinal and optic nerve diseases with Doppler Fourier domain optical coherence tomography (OCT).

Methods: Sixty-two participants were divided into five groups: normal, glaucoma, nonarteritic ischemic optic neuropathy (NAION), treated proliferative diabetic retinopathy (PDR), and branch retinal vein occlusion (BRVO). Doppler OCT was used to scan concentric circles of 3.4- and 3.75-mm diameters around the optic nerve head. Flow in retinal veins was calculated from the OCT velocity profiles. Arterial and venous diameters were measured from OCT Doppler and reflectance images.

Results: Total retinal blood flow in normal subjects averaged 47.6 μL/min. The coefficient of variation of repeated measurements was 11% in normal eyes and 14% in diseased eyes. Eyes with glaucoma, NAION, treated PDR, and BRVO had significantly decreased retinal blood flow compared with normal eyes (P < 0.001). In glaucoma patients, the decrease in blood flow was highly correlated with the severity of visual field loss (P = 0.003). In NAION and BRVO patients, the hemisphere with more severe disease also had lower blood flow.

Conclusions: Doppler OCT retinal blood flow measurements showed good repeatability and excellent correlation with visual field and clinical presentations. This approach could enhance our understanding of retinal and optic nerve diseases and facilitate the development of new therapies.

Figure 1.

(a) Fundus photograph showing the double circular pattern of the OCT beam scanning retinal blood vessels emerging from the optic disc. (b) The relative position of a blood vessel in the two OCT cross-sections is used to calculate the Doppler angle θ between the beam and the blood vessel. (c) Color Doppler OCT image showing the unfolded cross-section from a circular scan. Arteries and veins could be distinguished by the direction of flow as determined by the signs (blue or red) of the Doppler shift and the angle θ. Image magnification ratio is 3.39:1.00 (vertical/horizontal).

Figure 2.

Blood volume flow rate versus blood vessel diameter. Results are on a log-log scale. Solid line: best-fit result of linear regression (P < 0.001; R = 0.93). Dotted lines: 95% confidence interval limits to the fitted line (solid). The SD about the mean slope and intercept values of the linear fit are ±0.08 and ±0.15, separately.

Figure 3.

Relationship between visual field (VF) loss and retinal blood flow in optic nerve diseases. There was a significant correlation (P = 0.003; Y = 0.85 X − 34.48; R = 0.691) between the VF mean deviation and the total retinal blood flow in the glaucoma group. There were not enough NAION patients to compute the correlation.

Figure 4.

Color Doppler OCT of an eye with NAION. (a) Superior retinal hemisphere (left half of image) showed lower flow, 13.6 μL/min in 4 veins (yellow arrowheads), compared with the inferior retinal hemisphere (right half of image), where the flow was 18.7 μL/min in two veins (yellow arrowheads). N, nasal; S, superior; T, temporal; I, inferior. Visual field total deviation map (b) showed altitudinal defect in the inferior field (corresponding to the superior retinal hemisphere).

Figure 5.

Doppler OCT of an eye with superotemporal branch retinal vein occlusion. The fundus photograph (a) showed the associated retinal hemorrhage. The fluorescein angiogram (b) showed diffuse dye leakage along the occluded vein and blocked fluorescence associated with the hemorrhage. This eye also had previous panretinal photocoagulation for proliferative diabetic retinopathy; associated exudates, blot hemorrhages, and laser scars were also present. Color Doppler OCT (c) showed flow in three veins of the superior retinal hemisphere (yellow arrowheads, left) was 8.2 μL/min. Flow in the three veins of the inferior retinal hemisphere (yellow arrowheads, right) was 10.4 μL/min.