Morphometric analysis of small arteries in the human retina using adaptive optics imaging

Abstract

Objectives:The wall-to-lumen ratio (WLR) of retinal arteries is a recognized surrogate of end-organ damage due to aging and/or arterial hypertension. However, parietal morphometry remains difficult to assess in vivo. Recently, it was shown that adaptive optics retinal imaging can resolve parietal structures of retinal arterioles in humans in vivo. Here, using adaptive optics retinal imaging, we investigated the variations of parietal thickness of small retinal arteries with blood pressure and focal vascular damage.Methods:Adaptive optics imaging of the superotemporal retinal artery was done in 49 treatment-naive individuals [mean age (±SD) 44.9 years (±14); mean systolic pressure 132 mmHg (±22)]. Semi-automated segmentation allowed extracting parietal thickness and lumen diameter. In a distinct cohort, adaptive optics images of arteriovenous nicking (AVN; n = 12) and focal arteriolar narrowing (FAN; n = 10) were also analyzed qualitatively and quantitatively.Results:In the cohort of treatment-naive individuals, by multiple regression taking into account age, body mass index, mean, systolic, diastolic and pulse blood pressure, the WLR was found positively correlated to mean blood pressure and age which in combination accounted for 43% of the variability of WLR. In the cohort of patients with focal vascular damage, neither FANs or AVNs showed evidence of parietal growth; instead, at sites of FANs, decreased outer diameter suggestive of vasoconstriction was consistently found, while at sites of AVNs venous narrowing could be seen in the absence of arteriovenous contact.Conclusion:High resolution imaging of retinal vessels by adaptive optics allows quantitative microvascular phenotyping, which may contribute to a better understanding and management of hypertensive retinopathy.

Effect of Diffuse Luminance Flicker Light Stimulation on Total Retinal Blood Flow Assessed With Dual-Beam Bidirectional Doppler OCT

“…Further exploration of these effects in humans would require measurement of diameters in smaller arterioles and venules as well as capillaries, which may be possible only by adaptive optics technology. [47][48][49] To give an example for the alterations of flow conditions in one subject, the flow was plotted over the diameter in a log-log plot for all vessels of subject 6 at baseline conditions (Fig. 9a) and during stimulation with diffuse luminance flicker (Fig.…”

The clinical implications of recent studies on the structure and function of the retinal microvasculature in diabetes

“…For example, adaptive optics retinal imaging [111,112], en face optical coherence tomography angiography [113], Doppler optical coherence tomography [114], scanning laser Doppler flowmetry [115], spectral-domain optical coherence tomography [116], and sequential and diameter response analysis [117], are now being studied to further measure and analyse the detailed structure and functions of the retina (including the foveal capillary network, choroidal vasculature, blood flow, choroidal flow, wall:lumen ratio and retinal vessel responses to flickering light). These developments may offer an improved understanding of how early diabetic complications develop and offer improved risk stratification in clinical practice.…”

Segmentation of Retinal Arteries in Adaptive Optics Images

“…Such an approach enables us to control the distance of the curves to their reference line and improve the robustness to image noise. Finally, we also want to mention that this work has recently permitted us to establish relationships between morphometric measurements and clinical parameters [12].…”