Retinal Flow Research Articles

Learned optical flow for intra-operative tracking of the retinal fundus

PurposeSustained delivery of regenerative retinal therapies by robotic systems requires intra-operative tracking of the retinal fundus. We propose a supervised deep convolutional neural network to densely predict semantic segmentation and optical flow of the retina as mutually supportive tasks, implicitly inpainting retinal flow information missing due to occlusion by surgical tools.MethodsAs manual annotation of optical flow is infeasible, we propose a flexible algorithm for generation of large synthetic training datasets on the basis of given intra-operative retinal images. We evaluate optical flow estimation by tracking a grid and sparsely annotated ground truth points on a benchmark of challenging real intra-operative clips obtained from an extensive internally acquired dataset encompassing representative vitreoretinal surgical cases.ResultsThe U-Net-based network trained on the synthetic dataset is shown to generalise well to the benchmark of real surgical videos. When used to track retinal points of interest, our flow estimation outperforms variational baseline methods on clips containing tool motions which occlude the points of interest, as is routinely observed in intra-operatively recorded surgery videos.ConclusionsThe results indicate that complex synthetic training datasets can be used to specifically guide optical flow estimation. Our proposed algorithm therefore lays the foundation for a robust system which can assist with intra-operative tracking of moving surgical targets even when occluded.

The relation between aortic stiffness and retinal microvascular flow pulsatility is attenuated by higher vascular resistance in healthy adults

Aortic stiffness is associated with increased risk of cerebrovascular disease and cognitive impairments with aging, although the mechanism that contribute to this link are not well‐defined. Increases in carotid artery flow pulsatility coincide with elevated aortic stiffness and may contribute to microvascular brain damage, but studies confirming augmented flow pulsatility in the downstream microvasculature have been limited. Given the ability to assess the retinal microvasculature non‐invasively in humans and evidence that disease‐ and age‐related alterations in the retinal microvasculature mirror changes in the cerebral microvasculature, we examined the hypothesis that age‐related increases in aortic stiffness would be correlated with higher retinal arteriole flow pulsatility (systolic flow – diastolic flow / mean flow). Among 33 healthy adults (age range: 25–60 years, 47% women), aortic stiffness was assessed by carotid‐femoral pulse wave velocity (CFPWV). Retinal arteriole flow pulsatility was quantified using laser speckle flowgraphy before and during a reduction in retinal vascular resistance via 30 s of diffuse luminance flicker. Multiple regression analysis including CFPWV, mean arterial pressure (MAP), and heart rate (HR) as independent variables demonstrated that lower MAP and HR, but not higher CFPWV, were significant determinants of greater flow pulsatility at baseline (CFPWV: β=0.10, P=0.548; MAP: β= −0.40, P=0.021; HR: β= −0.50, P=0.002; model R2=0.43, P=0.001). However, after reducing retinal vascular resistance (P<0.001) via 30s of diffuse luminance flicker, multiple regression analysis demonstrated that higher CFPWV was a significant determinant of greater retinal arteriole flow pulsatility (β=0.35, P=0.026) in addition to lower MAP (β= −0.54, P=0.001) and HR (β= −0.43, P=0.005) (model R2=0.51, P<0.001). In summary, no relation was observed between higher CFPWV and retinal arteriole flow pulsatility at rest, but a positive relation was observed during arteriole vasodilation. These findings suggest that greater vascular resistance may be an important compensatory mechanism to reduce transmission of flow pulsatility.Support or Funding InformationAHA 17POST33440101, T32 HL07121 NHLBI (P01HL014388), U54 TR001356 and AHA (13DG143400012).

Quantitative assessment of the retinal microvasculature and choriocapillaris in myopic patients using swept-source optical coherence tomography angiography.

To study the retinal capillary microvasculature and the choriocapillaris (CC) in myopic eyes using swept-source optical coherence tomography angiography (SS-OCTA). Patients with high myopia (≥ - 6D; axial length ≥ 26.5mm), moderate myopia (≥ - 3D, < - 6D), and age-matched healthy subjects presenting to the Shanghai General Hospital and Doheny-UCLA Eye Centers were enrolled in this prospective, multicenter study. Any subjects with evidence of macular abnormalities suggestive of pathologic myopia were excluded. SS-OCTA at both sites was performed using a Zeiss PLEX Elite instrument with a 6 × 6mm scan pattern centered on the fovea. Two repeated volume scans were acquired for image averaging. The instrument pre-defined en face slab of the superficial and deep retinal capillary microvasculature was used to isolate and display the superficial and deep retinal capillaries. A slab spanning from 21 to 31μm deep to the RPE fit line was used to isolate and display the CC. The OCTA images were exported for averaging using Image J. Littmann's method and the Bennett formula were applied to adjust for the impact of magnification in the high and moderate myopia groups. The resultant images were then binarized. Though projection artifact removal software was used, regions below the large superficial retinal vessels were excluded for quantitative analyses of the deep retinal capillary plexus and the CC. Vessel density (VD) and vessel length density (VLD) of the superficial and deep retinal capillary plexus (SCP, DCP) and CC flow deficit (FD) were analyzed, quantified, and compared between different groups. Twenty-five eyes of 25 patients with high myopia, 25 eyes of 25 patients with moderate myopia, and 25 eyes of 25 normal age-matched controls were included in this study. The VD of the SCP was lower in the high myopia group compared with the emmetropic control groups (p < 0.05), but the VD of the DCP demonstrated no significant difference among the three groups (p > 0.05). The VLDs of the SCP were lower in the high and moderate myopia groups compared with the control group (p < 0.05), while the VLD of the DCP was lower in the high myopia group compared with the moderate myopia and emmetropic control group (p < 0.05). The CC FD% in the high myopia group was significantly greater than both the control and moderate myopia subjects (p < 0.05). Of note, the severity of the CC flow deficit was not correlated with choroidal thickness (p > 0.05). The retinal microvasculature may demonstrate alterations in highly myopia eyes. The CC in macular regions shows greater impairment in eyes with high myopia compared with eyes with lesser degrees of myopia, and these deficits are already present in the absence of features of pathologic or degenerative myopia. The threshold of CC FD leading to myopic maculopathy remains to be defined.

Short-Term Effects of Dark Chocolate on Retinal and Choriocapillaris Perfusion in Young, Healthy Subjects Using Optical Coherence Tomography Angiography.

(1) Aim: Contrasting results have been published on the effect of dark chocolate on visual function. The aim of this study was to evaluate retinal and choriocapillaris perfusion, using optical coherence tomography angiography (OCT-A), and visual function in healthy subjects following dark chocolate ingestion. (2) Methods: This prospective randomized study was carried out on 18 healthy young subjects at the St. Andrea Hospital, Sapienza, University of Rome. Visual acuity assessment and a complete ophthalmologic examination were carried out at baseline. In session one, each subject was randomized to eat either a 100 g dark chocolate bar or a 100 g white chocolate bar. In session two, the opposite chocolate was given to each participant. OCT-A and best corrected visual acuity (BCVA) were performed before the chocolate was eaten and repeated 1, 2, and 3 h after that. Retinal vessel density and choriocapillaris flow area were assessed. (3) Results: 18 patients with a mean (SD) age of 26.3 (1.5) years were included. No significant differences between dark or white chocolate were found when evaluating foveal density (%), whole density (%), choriocapillaris flow area, and BCVA. (4) Conclusions: Dark chocolate did not result in significant changes in retinal perfusion and choriocapillaris flow area. However, given the results of other studies showing the positive effects of flavonoids on visual function, further studies are warranted using pure chocolate without other components such as caffeine that can potentially affect results. Furthermore, we cannot rule out the possible benefits of higher doses of flavonoids in dietary supplementation over a more extended period and in a larger patient population.

Blood flow rate estimation in optic disc capillaries and vessels using Doppler optical coherence tomography with 3D fast phase unwrapping.

The retinal volumetric flow rate contains useful information not only for ophthalmology but also for the diagnosis of common civilization diseases such as diabetes, Alzheimer's disease, or cerebrovascular diseases. Non-invasive optical methods for quantitative flow assessment, such as Doppler optical coherence tomography (OCT), have certain limitations. One is the phase wrapping that makes simultaneous calculations of the flow in all human retinal vessels impossible due to a very large span of flow velocities. We demonstrate that three-dimensional Doppler OCT combined with three-dimensional four Fourier transform fast phase unwrapping (3D 4FT FPU) allows for the calculation of the volumetric blood flow rate in real-time by the implementation of the algorithms in a graphics processing unit (GPU). The additive character of the flow at the furcations is proven using a microfluidic device with controlled flow rates as well as in the retinal veins bifurcations imaged in the optic disc area of five healthy volunteers. We show values of blood flow rates calculated for retinal capillaries and vessels with diameters in the range of 12-150 µm. The potential of quantitative measurement of retinal blood flow volume includes noninvasive detection of carotid artery stenosis or occlusion, measuring vascular reactivity and evaluation of vessel wall stiffness.

Retinal Vascular Changes in Patients with Chronic Obstructive Pulmonary Disease: An Optical Coherence Tomography Angiography Study.

Objectives:In the current study, we aimed to investigate retinal vascular density and blood flow changes in patients with chronic obstructive pulmonary disease (COPD) using optical coherence tomography angiography (OCTA) (AngioVue Avanti, Optovue).Methods:Thirty eyes of 30 patients with COPD and 30 eyes of 30 healthy controls were evaluated with OCTA. Foveal and parafoveal vessel density, inner retinal and choriocapillary flow area, and foveal avascular zone (FAZ) area were measured and compared between the groups.Results:No statistically significant differences were observed in the outer retinal flow area and choriocapillary flow area measurements between the groups (p=0.609 and p=0.162, respectively). There was no statistically significant difference in FAZ and FAZ perimeter values between the groups (p=0.725 and p=0.820, respectively). Vascular density measurements in the superficial foveal and parafoveal areas were not statistically significantly different between the groups (p>0.05, for all). Deep parafoveal vascular density values of the COPD group were statistically significantly lower than the control group in all investigated areas except the superior and inferior quadrants.Conclusion:The results of our study demonstrated for the first time that vascular density decreased in the parafoveal area due to COPD-related hypoxemia and endothelial dysfunction.

Optic Flow, but Not Retinal Flow, Is Essential to Induce VR Sickness

Optic Flow, but Not Retinal Flow, Is Essential to Induce VR Sickness

Optic Flow, but Not Retinal Flow, Is Essential to Induce VR Sickness

Optic Flow, but Not Retinal Flow, Is Essential to Induce VR Sickness

Early retinal flow changes after vitreoretinal surgery in idiopathic epiretinal membrane using swept source optical coherence tomography angiography.

(1) Background: The aim of this observational cross-sectional work was to investigate early retinal vascular changes in patients undergoing idiopathic epiretinal membrane (iERM) surgery using swept source optical coherence tomography angiography (SS-OCTA); (2) Methods: 24 eyes of 24 patients who underwent vitrectomy with internal limiting membrane (ILM) peeling were evaluated pre- and postoperatively using SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). For each eye, five 6x6-mm OCTA volume scans were acquired by two observers independently. The en face images of superficial capillary plexus (SCP) were then exported to imageJ and a semi-automated algorithm was used for subsequent quantitative analysis. Perfusion density (PD), vessel length density (VLD), vessel diameter index (VDI) and vessel tortuosity (VT) of SCP were evaluated in both the parafoveal (2.5 mm diameter) and perifoveal areas (5.5 mm diameter); (3) Results: At OCTA analysis statistically significant differences were found between controls and diseased eyes for all parameters in parafoveal and perifoveal regions (p < 0.001; p < 0.05) except for perifoveal VLD. During 6-month follow up, both anatomical/perfusion and functional parameters showed a statistically significant improvement if compared to preoperative values. In detail, at one-month post vitrectomy, VLD and VT significantly changed in parafoveal region (p = 0.043; p = 0.045), while PD and VDI showed a trend of increase in both parafoveal and perifoveal region. At 6 months after surgery, PD, VLD and VT of parafoveal region significantly improved (p = 0.021, p = 0.018, p = 0.047 respectively). (4) Conclusions: SS-OCTA provides a quantitative and qualitative analysis of the superficial capillary plexus allowing for early vascular changes assessment after vitrectomy with iERM and ILM peeling.

Retinal optic flow and the control of locomotion

A long history of research on the visual control of locomotion has explored the role of optic flow in the regulation and guidance of human walking. It is generally agreed that the head-centered Focus of Expansion (FoE) lies in a stable location in the walker’s direction of travel, and that humans use this feature to control heading. We used optic flow estimation algorithms to measure head-centered optic flow recorded from the head-mounted camera of a mobile eye tracker of subjects walking in real-world environments. Contrary to the traditional view, we found natural head oscillations during locomotion cause the FoE to move constantly at high velocities within the walker’s field of view. Thus strategies that suggest the FoE is used for heading could not be implemented on the basis of naturally occurring optic flow. In contrast, we found that retinal optic flow contains information that may be used for the control of locomotion. Fixation nulls motion at the fovea, resulting in regular patterns of outward flow across the retina that encode information about the walker’s movement relative to the fixated location. Analyzing retinal flow fields using the curl and divergence operators from vector calculus reveals features that are directly applicable for the control of locomotion. For instance, the sign of retinal curl (which corresponds clockwise/counter clockwise rotation) indicates whether the walker will pass to the left or right of the point they are fixating. In addition, the walkers’ instantaneous, world-centered velocity vector may be derived directly from the divergence across the retinal flow field. These features provide a much richer and more stable source of information for the control of locomotion than the FoE. Furthermore, this information can be extracted directly from retinotopic visual motion, so a coordinate transform into head-centered coordinates is unnecessary.

Characterization of natural head and eye movements driving retinal flow

Characterization of natural head and eye movements driving retinal flow

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY FINDINGS IN PATIENTS WITH NONOCULAR BEHÇET DISEASE.

To describe the optical coherence tomography angiography findings in nonocular Behçet disease. The superficial capillary plexus (SCP) and deep capillary plexus (DCP) and outer retinal and choroidal flow were evaluated using optical coherence tomography angiography. Perimetry was performed to correlate any microvascular and functional changes. Capillary nonperfusion areas were found in the superficial capillary plexus in 16/20 eyes (80%) and in the DCP in 17/20 eyes (85%). Perifoveal capillary arcade disruption and vessel rarefaction were present in both plexuses in all cases. Capillary telangiectasia was present in the superficial capillary plexus in five eyes (25%) and in the DCP in all eyes. Telangiectasia of the parafoveal capillaries was present in the DCP in all eyes. The mean area of the foveal avascular zone was not significantly different from that in 20 normal eyes (P = 0.68). However, mean and central subfield capillary density values were significantly lower (P < 0.001 and P < 0.005, respectively) in the Behçet disease group. Perimetry revealed central scotomata on the pattern deviation plot in 12 eyes (60%). Telangiectasia of the parafoveal capillaries was detected in the DCP in all cases. Microvascular changes in the superficial capillary plexus and DCP in nonocular Behçet disease can be detected by optical coherence tomography angiography.

Widefield Swept-Source Optical Coherence Tomography Angiography of Proliferative Diabetic Retinopathy.

To demonstrate the utility of widefield swept-source optical coherence tomography angiography (SS-OCTA) for the diagnosis and management of proliferative diabetic retinopathy (PDR). Consecutive patients with vision-threatening diabetic retinopathy were imaged with widefield SS-OCTA using the 12 mm × 12 mm scan pattern. Twenty-four eyes of 12 patients underwent SS-OCTA imaging. In all 24 eyes, the en face total retinal flow images detected areas of decreased retinal perfusion, and the en face vitreoretinal interface (VRI) slabs detected foci of retinal neovascularization (NV). NV was treated and followed using the VRI images. Widefield SS-OCTA is a useful, noninvasive technology for the detection and monitoring of NV in PDR. Features of interest, such as areas of decreased retinal perfusion, increased retinal thickness, and NV, can be identified from different en face slabs extracted from a single 12 mm × 12 mm scan. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:474-484.].

AORTIC STIFFNESS IS NOT ONLY ASSOCIATED WITH STRUCTURAL BUT ALSO WITH FUNCTIONAL PARAMETERS OF MICROCIRCULATION

Objective: The aim of the study was to test the hypothesis if arterial stiffness is linked to reduction of retinal capillary blood flow and development of retinal microvascular remodelling. Design and method: The study group comprised of 88 patients with essential hypertension (n = 88, 54.3 ± 8.3 years, 44.3% were female) and 32 healthy controls. Inclusion criteria were: essential hypertension, age of 40–70 years old. Exclusion criteria were: secondary hypertension, any cardiovascular disease including heart failure, coronary artery disease, arrhythmia, moderate or severe valve disease, history of stroke or transient ischemic attack, chronic kidney disease with eGFR < 60 mml/min/1.73 m2, diabetes mellitus, eye disease, pregnancy. Retinal microcirculation was evaluated by scanning laser Doppler flowmetry. Macrovascular changes were assessed on the basis of measurement of arterial stiffness (by carotid-femoral pulse wave velocity, central pulse pressure, augmentation pressure and augmentation index) and intima media thickness of common carotid artery. Diastolic dysfunction and left ventricular hypertrophy were analysed by echocardiography. Results: Pulse wave velocity was inversely correlated with mean retinal capillary blood flow in a group of hypertensive patients (R = −0.32, p < 0.01). This relationship remained significant in multivariate regression analysis even after adjustment for age, systolic blood pressure and waist to hip ratio (β = −40.275, p < 0.001). Central pulse pressure was positively correlated with retinal wall thickness (R = 0.44, p < 0.05), wall cross sectional area (R = 0.44, p < 0.05) and wall to lumen ratio (R = 0.43, p < 0.05). Brachial pulse pressure was positively correlated with wall thickness (R = 0.43, p < 0.05), wall cross sectional area (R = 0.41, p < 0.05) and wall to lumen ratio (R = 0.47, p < 0.05). In contrast, the relationship between augmentation pressure or augmentation index and structural indicators of retinal remodelling was not observed. Conclusions: In conclusion, the study provides an evidence that microcirculation is coupled with macrocirculation not only in terms of structural but also functional parameters. Pulse wave velocity was independently associated with retinal capilary flow. Central and brachial pulse pressure were significantly related to retinal wall thickness, wall cross sectional area and wall to lumen ratio.

EFFECTS OF THE NO SYNTHASE INHIBITOR RONOPTERIN (VAS203) ON MICRO- AND MACROCIRCULATION IN HEALTHY VOLUNTEERS

Objective: The tetrahydrobiopterin-analogue VAS203, an in vivo inhibitor of predominantly the inducible nitric oxide synthase (iNOS), was developed to reduce secondary damage in patients with severe traumatic brain injury. However, its effect on micro- and macrocirculation is less well established. The aim of the present study was to characterize in detail the pharmacological effects of VAS203 on micro- and macrocirculation in humans. Design and method: In this single-centre, double-blind, randomized, placebo-controlled cross-over phase I study 16 healthy male subjects were included. A constant infusion of VAS203 (total 10 mg/kg body weight) or placebo was administered for 6 hours. After a wash-out phase of 28 days the second course with either placebo or VAS203 was applied. Renal hemodynamics were assessed with constant-infusion input-clearance technique with para-aminohippuric acid (PAH) for renal plasma flow (RPF). In addition, we assessed retinal capillary flow, as microvascular parameter by scanning laser Doppler flowmetry (SLDF) at 670 nm and used pulse wave analysis by SphygmoCorTM device for assessment of central systolic pressure, as macrovascular parameter of systemic circulation. Results: Intravenous infusion of VAS203 resulted in a reduction of RPF, but remained unchanged with placebo (Figure), resulting in a significant decrease of RPF with VAS203 compared to placebo (p < 0.0001).In contrast, mean retinal capillary flow (mirroring cerebral circulation) remained preserved at any time-point during as well as up to 2 hours after intravenous infusion of VAS203 (all p > 0.4). Compared to placebo, there was no change of brachial blood pressure due to VAS203 infusion (p > 0.2). In addition, no significant effect of VAS203 infusion on central systolic pressure was observed, indicative of no clinical meaningful effects of VAS203 on systemic circulation (p > 0.1). Conclusions: Our phase I study in humans indicate that a dose of 10 mg/kg body weight VAS203 reduces renal perfusion within a physiological range, but has no other acute effects on assessed parameters of micro- and macrocirculation.

VASCULAR REMODELING OF RETINAL VESSELS IN PATIENTS WITH CONGESTIVE HEART FAILURE

Objective:Detailed analysis of retinal capillary flow (RCF) and vascular parameters in the retinal circulation allows us to differentiate between eutrophic and hypertrophic remodeling. In previous studies, we found that hypertensive patients with type 2 diabetes mellitus (T2DM) mostly suffer from hy

Automated retinal microvascular velocimetry based on erythrocyte mediated angiography.

Retinal blood flow is an emerging biomarker in ocular and systemic disease. Erythrocyte mediated angiography (EMA) is a novel technique that provides an easily interpretable blood flow velocity quantification by directly tracing individual moving erythrocyte ghosts over time in vivo, imaged using a scanning laser ophthalmoscope (Heidelberg Retina Angiograph platform). This tracking procedure, however, requires time-consuming manual analysis to determine blood flow. To overcome this current bottleneck, we developed an objective and automated velocimetry approach, EMA - Automated Velocimetry (EMA-AV), which is based on a modified sequential Monte Carlo method. The intra-class correlation coefficient (ICC) between trained human graders and EMA-AV is 0.98 for mean vessel velocity estimation and 0.92 for frame by frame erythrocyte velocity estimation. This study proves EMA-AV is a reliable tool for quantification of retinal microvascular velocity and flow and establishes EMA-AV as a reliable and interpretable tool for quantifying retinal microvascular velocity.

Multi-scale and -contrast sensorless adaptive optics optical coherence tomography.

The roles of the retinal microvasculature and the retinal pigment epithelium (RPE) in maintaining the health and metabolic activity of the retina lend great clinical value to their high-resolution visualization. By integrating polarization diversity detection (PDD) into multi-scale and -contrast sensorless adaptive optics optical coherence tomography (MSC-SAO-OCT), we have developed a novel multi-contrast SAO OCT system for imaging pigment in the RPE as well as flow in the retinal capillaries using OCT angiography (OCTA). Aberration correction was performed based on the image quality using transmissive deformable optical elements. MSC-SAO-OCTA imaging was performed at multiple fields-of-view (FOVs) with adjustable numerical aperture (NA). Retinal flow and RPE structural images for in vivo healthy and pathological human posterior eyes were demonstrated to show clinical feasibility of the system. High-resolution imaging of retinal vasculature at both large and small FOVs, as well as characterization of RPE topology and deformation, enables more sophisticated and concise investigation of retinal pathologies for in vivo human imaging. MSC imaging may permit detection and analysis of even subtle deformations in the RPE layer using a single instrument.

Optische Kohärenztomographie-Angiographie als zukünftiges Diagnostikum in der Sportmedizin?

High-intensity interval training (HIIT) proved to be efficient for increasing health-related fitness in general and in patients with life style-induced chronic diseases. This study aimed to evaluate if (I)individual physical fitness and (II)aHIIT intervention affects optical coherence tomography angiography (OCTA) measurements at the ocular fundus of healthy young adults. A total of 65 healthy participants performed astandardized incremental running test to determine their physical fitness. This was defined as speed at the individual anaerobic threshold and maximum running speed followed by a4-week HIIT with two exercise sessions/week. The OCTA measurements of the foveal avascular zone (FAZ) and flow densities in various segments of the macula and optic nerve head were performed at rest before and after HIIT. An inverse correlation between individual fitness and FAZ area was detected. No further correlations between individual physical fitness and other OCTA parameters were found. In response to HIIT the mean FAZ area in the deep retinal plexus and macular flow density of the superficial layer decreased by 14.00 ± 13.02% and 1.26 ± 3.20%, respectively. The flow density of the nerve head layer in the peripapillary area showed an increase of 1.94 ± 2.39%. All other parameters showed no differences between measurements before and after HIIT. Differences were found in the OCTA measurements of the FAZ depending on the individual physical fitness. Performing HIIT can induce significant changes in certain OCTA parameters. Therefore, OCTA imaging appears to be apromising imaging modality in the field of sports medicine.

Generating retinal flow maps from structural optical coherence tomography with artificial intelligence

Despite advances in artificial intelligence (AI), its application in medical imaging has been burdened and limited by expert-generated labels. We used images from optical coherence tomography angiography (OCTA), a relatively new imaging modality that measures retinal blood flow, to train an AI algorithm to generate flow maps from standard optical coherence tomography (OCT) images, exceeding the ability and bypassing the need for expert labeling. Deep learning was able to infer flow from single structural OCT images with similar fidelity to OCTA and significantly better than expert clinicians (P < 0.00001). Our model allows generating flow maps from large volumes of previously collected OCT data in existing clinical trials and clinical practice. This finding demonstrates a novel application of AI to medical imaging, whereby subtle regularities between different modalities are used to image the same body part and AI is used to generate detailed inferences of tissue function from structure imaging.