Considerations in the Understanding of Venous Outflow in the Retinal Capillary Plexus

Comparison of Vessel Density Reduction in the Deep and Superficial Capillary Plexuses in Branch Retinal Vein Occlusion

PURPOSE

To quantify the susceptibility of the deep capillary plexus (DCP) in comparison with that of the superficial capillary plexus (SCP) in eyes with branch retinal vein occlusion (BRVO) using swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

SS-OCTA (TritonTM; Topcon, Tokyo, Japan) scans (3 × 3 mm) of 41 patients with BRVO were retrospectively analyzed. The mean vessel densities (VDs) of the SCP and the DCP were calculated in eyes with BRVO using the ImageJ program (National Institutes of Health, Bethesda, MD, USA) and compared with those in the normal fellow eye without any morbidity or unaffected sector in the BRVO eye.

RESULTS

The reduction rate of mean VD in SCP and DCP between the affected and unaffected sector of eyes with BRVO was 13.88 and 24.60%, respectively. Additionally, the reduction rate of mean VD in the SCP and DCP in the affected sector of BRVO eyes versus the corresponding sector of fellow eyes was 13.31 and 24.49%, respectively.

CONCLUSION

The DCP was 1.77-1.84 times more affected than the SCP by ischemic damage in eyes with BRVO.

Association of Optical Coherence Tomography Angiography of Collaterals in Retinal Vein Occlusion With Major Venous Outflow Through the Deep Vascular Complex

Importance

Analysis of collateral vessel formation following retinal vein occlusion may advance our understanding of the venous outflow anatomy in the macula.

Objective

To determine the location of collateral vessels with optical coherence tomography (OCT) angiography imaging.

Design, Setting, and Participants

Observational retrospective cohort study. Collateral vessel formation was studied with OCT angiography (OCTA) in patients with retinal vein occlusion (RVO). The study took place at 2 retinal practices (Vitreous Retina Macula Consultants of New York and Stein Eye Institute, University of California, Los Angeles), with patient records retrieved from March 2015 to August 2017. Data analysis was completed in November 2017.

Exposures

Collaterals identified with fundus photography and/or fluorescein angiography were analyzed with OCTA to determine their course through the superficial vascular plexus (SVP) and the deep vascular complex (DVC).

Main Outcomes and Measures

Collateral vessel pathways through the SVP and DVC were analyzed with cross-sectional and en face OCT and OCTA segmentation and color-coded volume renderings prepared from raw OCTA voxel data.

Results

From 23 eyes (22 branch and 1 hemispheric retinal vein occlusion ) of 23 patients (mean [SD] age, 73 [11] years), 101 collateral vessels were identified and analyzed (mean [SD], 4.4 [2.0]; range, 2-9 collateral per eye). On OCTA, the collaterals appeared as curvilinear dilated flow signals that connected veins across the horizontal raphe or veins on opposite sides of an occluded venous segment within the same retinal hemisphere. Of the 101 collaterals analyzed, all showed greater flow signal in the DVC, and all had some portion of their course identified within the DVC. No collaterals were found exclusively in the SVP. Volume renderings for 3 cases confirmed qualitatively that retinal collateral vessels course through the retina predominantly at the level of the DVC.

Conclusions and Relevance

Based on a limited number of cases, all collateral vessels associated with retinal vein occlusion were found to course through the DVC. The absence of collaterals isolated to the SVP supports a serial arrangement of the SVP and DVC, with venous drainage predominantly coursing through the DVC.

Radial Hemorrhage in Henle Layer in Macular Telangiectasia Type 2

Importance

Radial hemorrhage in the outer plexiform layer of Henle may be a complication of macular telangiectasia type 2 (MacTel 2) and may occur because of microvascular abnormalities of the deep retinal capillary plexus in the absence of subretinal neovascularization.

Objective

To describe the multimodal imaging findings, including cross-sectional and en face optical coherence tomography (OCT), of radial hemorrhage in the outer plexiform layer of Henle, which may be a complication of MacTel 2.

Design, Setting, and Participants

This retrospective case series from 2 tertiary referral centers (Stein Eye Institute, Los Angeles, California; New England Eye Center, Boston, Massachusetts) between January 1, 2012, and December 31, 2017, describes 3 patients with MacTel 2 complicated by characteristic radial hemorrhage in the outer plexiform layer of Henle.

Main Outcomes and Measures

Color fundus photography, cross-sectional and en face OCT, OCT angiography (OCTA), fundus autofluorescence, and fluorescein angiography.

Results

Three male patients presented with sudden vision loss in the right eye. A characteristic radial pattern of hemorrhage was noted with color fundus photography. Cross-sectional and en face OCT and OCTA localized the hemorrhage to the outer plexiform layer of Henle in the absence of subretinal neovascularization. Optical coherence tomography findings consistent with MacTel 2 were identified in the fellow eye in each patient. At the follow-up visit 1 to 2 months after presentation, spontaneous resolution of the hemorrhage was noted in all 3 patients, and OCTA illustrated underlying microvascular abnormalities in the deep retinal capillary plexus in 2 patients.

Conclusions and Relevance

This report describes 3 patients with MacTel 2 complicated by characteristic radial hemorrhage in the outer plexiform layer of Henle, which may represent a characteristic finding in MacTel 2 that may develop as a result of microvascular abnormalities of the deep retinal capillary plexus in the absence of subretinal neovascularization.

Association Between Vessel Density and Visual Acuity in Patients With Diabetic Retinopathy and Poorly Controlled Type 1 Diabetes

Importance

Capillary dropout is a hallmark of diabetic retinopathy, but its role in visual loss remains unclear.

Objective

To examine how macular vessel density is correlated with visual acuity (VA) in patients younger than 40 years who have type 1 diabetes without macular edema but who have diabetic retinopathy requiring panretinal photocoagulation.

Design, Settings, and Participants

Retrospective cohort study of VA and optical coherence tomography angiography data collected from consecutive patients during a single visit to Lariboisière Hospital, a tertiary referral center in Paris, France. The cohort included 22 eyes of 22 patients with type 1 diabetes without macular edema but with bilateral rapidly progressive diabetic retinopathy that was treated with panretinal photocoagulation between August 15, 2015, and December 30, 2016. Eyes were classified into 2 groups by VA: normal (logMAR, 0; Snellen equivalent, 20/20) and decreased (logMAR, >0; Snellen equivalent, <20/20). The control group included 12 eyes from age-matched healthy participants with normal vision.

Main Outcomes and Measures

Visual acuity and mean vessel density in 4 retinal vascular plexuses: the superficial vascular plexus and the deep capillary complex, which comprises the intermediate capillary plexus and the deep capillary plexus.

Results

Of the 22 participants, 11 (50%) were men, mean (SD) age was 30 (6) years, and mean (SD) hemoglobin A1c level was 8.9% (1.6%). Of the 22 eyes with diabetic retinopathy, 13 (59%) had normal VA and 9 (41%) had decreased VA (mean [SD]: logMAR, 0.12 [0.04]; Snellen equivalent, 20/25). Mean [SE] vessel density was lower for eyes with diabetic retinopathy and normal VA compared with the control group in the superficial vascular plexus (44.1% [0.9%] vs 49.1% [0.9%]; difference, -5.0% [1.3%]; 95% CI, -7.5% to -2.4%; P < .001), in the deep capillary complex (44.3% [1.2%] vs 50.6% [1.3%]; difference, -6.3% [1.8%]; 95% CI, -9.9% to -2.7%; P = .001), in the intermediate capillary plexus (43.8% [1.2%] vs 49.3% [1.2%]; difference, -5.5% [1.7%]; 95% CI, -9.0% to -2.0%; P = .003), and in the deep capillary plexus (24.5% [1.0%] vs 30.5% [1.0%]; difference, -6.1% [1.4%]; 95% CI, -8.9% to -3.2%; P < .001). Mean vessel density was lower in eyes with diabetic retinopathy and decreased VA compared with eyes with diabetic retinopathy and normal VA; the mean (SE) loss was more pronounced in the deep capillary complex (34.6% [1.5%] vs 44.3% [1.2%]; difference, -9.6% [1.9%]; 95% CI, -13.6% to -5.7%; P < .001), especially in the deep capillary plexus (15.2% [1.2%] vs 24.5% [1.0%]; difference, -9.3% [1.5%]; 95% CI, -12.4% to -6.1%; P < .001), than in the superficial vascular plexus (39.6% [1.1%] vs 44.1% [0.9%]; difference, -4.5% [1.4%]; 95% CI, -7.3% to -1.7%; P = .002).

Conclusions and Relevance

These data suggest that in patients with type 1 diabetes without macular edema but with severe nonproliferative or proliferative diabetic retinopathy, decreased VA may be associated with the degree of capillary loss in the deep capillary complex.

Congenital Retinal Macrovessel and the Association of Retinal Venous Malformations With Venous Malformations of the Brain

Importance

Congenital retinal macrovessel (CRM) is a rarely reported venous malformation of the retina that is associated with venous anomalies of the brain.

Objective

To study the multimodal imaging findings of a series of eyes with congenital retinal macrovessel and describe the systemic associations.

Design, Setting, and Participants

In this cross-sectional multicenter study, medical records were retrospectively reviewed from 7 different retina clinics worldwide over a 10-year period (2007-2017). Patients with CRM, defined as an abnormal, large, macular vessel with a vascular distribution above and below the horizontal raphe, were identified. Data were analyzed from December 2016 to August 2017.

Main Outcomes and Measures

Clinical information and multimodal retinal imaging findings were collected and studied. Pertinent systemic information, including brain magnetic resonance imaging findings, was also noted if available.

Results

Of the 49 included patients, 32 (65%) were female, and the mean (SD) age at onset was 44.0 (20.9) years. A total of 49 eyes from 49 patients were studied. Macrovessel was unilateral in all patients. Color fundus photography illustrated a large aberrant dilated and tortuous retinal vein in all patients. Early-phase frames of fluorescein angiography further confirmed the venous nature of the macrovessel in 40 of 40 eyes. Optical coherence tomography angiography, available in 17 eyes (35%), displayed microvascular capillary abnormalities around the CRM, which were more evident in the deep capillary plexus. Of the 49 patients with CRM, 39 (80%) did not illustrate any evidence of ophthalmic complications. Ten patients (20%) presented with retinal complications, typically an incidental association with CRM. Twelve patients (24%) were noted to have venous malformations of the brain with associated magnetic resonance imaging. Of these, location of the venous anomaly in the brain was ipsilateral to the CRM in 10 patients (83%) and contralateral in 2 patients (17%), mainly located in the frontal lobe in 9 patients (75%).

Conclusions and Relevance

Our study has identified an association between macrovessels in the retina and venous anomalies of the brain (24% compared with 0.2% to 6.0% in the normal population). Thus, we recommend new guidelines for the systemic workup of patients with CRM to include brain magnetic resonance imaging with contrast. These lesions may be more accurately referred to as retinal venous malformations, which may raise awareness regarding potential cerebral associations.

Misery Perfusion, Diffusive Oxygen Shunting and Interarterial Watershed Infarction Underlie Oxygenation-Based Hypoperfusion Maculopathy

PURPOSE

To describe and explain the entire range of acute ischemic macular damage that follows panretinal hypoperfusion from central retinal artery or vein occlusion.

DESIGN

Perspective article.

METHODS

To correlate the fundoscopic, fluorescein angiographic, oximetric, and optical coherence tomographic (OCT) features developing within the posterior inner retina following incremental reductions in arteriovenous perfusion pressure across the retinal circulation.

RESULTS

The spectrum of acute oxygenation-based hypoperfusion maculopathy (OHM) is consistent with that predictable from a modified Krogh cylinder model of tissue oxygenation. Diffusive oxygen shunting plays a significant role in the "artery-dominated" generation of ischemic signs during misery perfusion. Three major grades of OHM severity can be discerned according to the predominant oxygenation status of ganglion cells within the superficial inner retina, whether this is normoxic (OHM1), hypoxic (OHM2), or anoxic (OHM3). Densely opaque axoplasmic sentinels are arranged along normoxic/hypoxic interfaces in OHM2. In OHM1 and OHM2, relative hypermetabolism and interarterial watershed infarction of fundal interneurons (WIFI) underpin subtle middle-retinal opacification with periarterial sparing. The fundal signs are optimally displayed en face using autofluorescence imaging whereas cross-sectional OCT reveals Paques' plaque formation.

CONCLUSIONS

An exquisite and supremely accessible exhibition of classical oxygen physiopathology unfolds in eyes with panretinal hypoperfusion courtesy of the transparent ocular media and the pattern of macular neuroretinal opacification that evolves as upstream tissues extract oxygen to the detriment of tissues downstream. Recent attempts to overrule the simple conceptual framework embodied in WIFI have no plausible anatomical nor physiological basis. Overreliance on OCT can result in misdiagnosis.

Optical Coherence Tomography Angiography of Macula in Chronic Anterior Ischaemic Optic Neuropathy Associated with Giant Cell Arteritis

A 74-year-old man presented with bilateral optic nerve atrophy related to arteritic anterior ischaemic optic neuropathy (AION) which started 22 years ago. Atrophic papilla was noted in both eyes and optical coherence tomography showed thinning of the retinal nerve fibres layer as well as the macular ganglion cell complex. Optical coherence tomography angiography of the macula found a decreased density of the superficial capillary complex, whereas deep capillary complex was well-preserved. Inner retinal layer atrophy in chronic arteritic AION is followed by a loss of vascularisation in these layers as a consequence of the neurodegeneration.

Three-Dimensional Microscopy Demonstrates Series and Parallel Organization of Human Peripapillary Capillary Plexuses

Purpose

To define the three-dimensional topologic organization of the human peripapillary capillary plexuses in order to better understand the hemodynamic characteristics of this retinal circulation.

Methods

The retinal microvasculature was perfusion labeled in five normal human donor eyes, and optical stacks were collected from regions immediately superior, temporal, inferior, and nasal to the optic disk by using confocal scanning laser microscopy. The spatial location and morphometric characteristics of capillary plexuses were compared. Three-dimensional visualization strategies were used to document the organization of vascular conduits that interconnect capillary beds and to study the communications between capillary beds and precapillary arterioles and postcapillary venules.

Results

The peripapillary microcirculation is composed of four capillary plexuses, including the radial peripapillary capillary plexus at the level of the nerve fiber layer, the superficial capillary plexus (SCP) at the level of the ganglion cell layer, the intermediate capillary plexus located at the inner boundary of the inner nuclear layer, and the deep capillary plexus located at the outer boundary of the inner nuclear layer. Capillary diameter and density were significantly different between the four plexuses (both P ≤ 0.011). The SCP is the only capillary bed that receives feeding and draining branches directly from precapillary arterioles and postcapillary venules, respectively. Four different inflow and outflow patterns characterized the communication between the SCP and surrounding capillary beds.

Conclusions

The capillary plexuses of the human peripapillary microcirculation are arranged in series and parallel and manifest specializations that likely reflect the unique metabolic demands and biochemical environment of the retinal layers.

An overview of optical coherence tomography angiography and the posterior pole

Optical coherence tomography angiography is a relatively new, noninvasive technology that has revolutionized imaging of the retinal and choroidal microvasculature. This technology is based on the detection of movement or changes that represent moving red cells in sequential optical coherence tomography scans. As with other established imaging technologies, it has unique benefits as well as certain disadvantages, which include a limited field of view and vulnerability to imaging artifacts. However, software and hardware improvements are continually evolving to mitigate these limitations. Optical coherence tomography angiography has been used to gain a better understanding of microvascular changes across a spectrum of ocular diseases including diabetic retinopathy, age-related macular degeneration, glaucoma, and retinal vein occlusions. In this article, we review algorithms and techniques commonly utilized in optical coherence tomography angiography systems and compare optical coherence tomography angiography to fluorescein angiography, the current gold standard for imaging the retinal vasculature. In addition, we provide an overview of important optical coherence tomography angiography findings in a variety of ocular diseases. Although the clinical role of this technology is still poorly defined, optical coherence tomography angiography has the potential to become an invaluable tool in the diagnosis and monitoring of vascular pathologies.

Pearls and Pitfalls of Optical Coherence Tomography Angiography Imaging: A Review

Optical coherence tomography angiography (OCTA) has significantly expanded our knowledge of the ocular vasculature. Furthermore, this imaging modality has been widely adopted to investigate different ocular and systemic diseases. In this review, a discussion of the fundamental principles of OCTA is followed by the application of this imaging modality to study the retinal and choroidal vessels. A proper comprehension of this imaging modality is essential for the interpretation of OCTA imaging applications in retinal and choroidal disorders.

A proposed mechanism influencing structural patterns in X-linked retinoschisis and stellate nonhereditary idiopathic foveomacular retinoschisis

OBJECTIVE

To explore the structural differences between X-linked retinoschisis (XLR) and stellate nonhereditary idiopathic foveomacular retinoschisis (SNIFR) using swept-source optical coherence tomography angiography (SS-OCTA).

METHODS

A case series of two patients, a 9-year-old male with XLR and a 58-year-old woman with SNIFR were imaged with swept-source optical coherence tomography angiography (SS-OCTA; PLEX Elite 900, Carl Zeiss Meditec, Inc, Dublin, CA). Automated segmentation was manually adjusted to include the areas of retinoschisis within en face flow and structural slabs. The flow data were binarized using ImageJ 1.51s (Wayne Rasband, National Institutes of Health, USA, http://imagej.nih.gov.ij ) and superimposed onto the structural slab.

RESULTS

In the eye with XLR, OCTA flow data superimposed on the structural slab demonstrated flow signal within numerous bridging structures connecting the inner and outer plexiform layers containing the intermediate (ICP) and deep (DCP) capillary plexuses. In contrast, the same technique applied to the eye with SNIFR demonstrated an absence of flow signal in the cystic retinal spaces within Henle's fiber layer.

CONCLUSIONS

The vascular pattern of bridging vessels between the ICP and DCP is closely related to the structural "retinoschisis" pattern of XLR and appears to be structurally different from that seen in SNIFR. Moreover, the connecting vessels appear to be highly represented and regularly distributed, thereby supporting a serial arrangement of the retinal capillary plexuses within the perifoveal macula.

Rodent retinal circulation organization and oxygen metabolism revealed by visible-light optical coherence tomography

Visible light optical coherence tomography (vis-OCT) is an emerging label-free and high-resolution 3-dimensional imaging technique that can provide retinal oximetry, angiography, and flowmetry in one modality. In this paper, we studied the organization of the arterial and venous retinal circulation in rats using vis-OCT. Arterioles were found predominantly in the superficial vascular plexus whereas veins tended to drain capillaries from the deep capillary plexus. After that, we determined the oxygen metabolic rate supported by retinal microcirculation by combining retinal vessel oxygen saturation and blood flow measurements. The ability to visualize and monitor retinal circulation organization and oxygen metabolism by vis-OCT may provide new opportunities for understanding the pathology of ocular diseases.

Paracentral Acute Middle Maculopathy and the Ischemic Cascade Associated With Retinal Vascular Occlusion

PURPOSE

To analyze the spectrum of ischemia associated with paracentral acute middle maculopathy (PAMM) in eyes with acute retinal vascular occlusion and to describe an ischemic cascade.

DESIGN

A retrospective observational case series.

METHODS

Patients presenting with PAMM secondary to acute retinal vascular occlusion were identified. Analysis of multimodal imaging was performed at baseline and at follow-up visits to elucidate the patterns and progression of ischemia within the retinal layers.

RESULTS

Multimodal retinal imaging from 16 eyes of 16 patients with acute retinal vascular occlusion associated with PAMM was studied. Analysis of en face optical coherence tomography (OCT) segmentation of the inner nuclear layer (INL) identified distinct patterns of PAMM correlating with the severity of ischemia and not the type of occlusion. A perivenular fern-like PAMM pattern was associated with better visual outcomes (average final visual acuity was 20/25). This pattern was noted to sequentially progress in 2 cases to a diffuse globular PAMM pattern in the INL, or to a pattern of ischemia involving both the middle and inner retinal layers with commensurate vision loss. Globular patterns of PAMM or ischemia involving both the middle and inner retina correlated with poorer visual outcomes (average final visual acuity was counting fingers at 5.5 ft). These various patterns of ischemia developed in eyes with retinal vascular occlusions in which blood flow through the retinal capillary plexuses was present but was significantly reduced and delayed.

CONCLUSIONS

This study describes OCT findings suggestive of an ischemic cascade in eyes with retinal vascular occlusion. The middle retina at the level of the deep capillary plexus, especially at the venular pole, may be more vulnerable to ischemic injury.

PARACENTRAL ACUTE MIDDLE MACULOPATHY IN A PERIVENULAR FERN-LIKE DISTRIBUTION WITH EN FACE OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To report a case of central retinal vein occlusion resulting in a perivenular pattern of paracentral acute middle maculopathy lesions best identified with en face optical coherence tomography (OCT).

METHODS

Retrospective case report. Optos ultra-widefield fluorescein angiography, spectral domain OCT, en face OCT, and OCT angiography were performed.

RESULTS

A 41-year-old man presented with decreased vision in the right eye for 2 weeks. Funduscopic examination of the affected right eye was notable for subtle retinal whitening in the macula, mild retinal venous dilation and tortuosity, and few scattered retinal dot and blot hemorrhages consistent with an acute central retinal vein occlusion. Widefield fluorescein angiography demonstrated delayed arterial and venous filling but no evidence of significant peripheral retinal vascular ischemia. En face OCT segmented at the inner nuclear layer illustrated a remarkable and precise perivenular distribution of fern-like paracentral acute middle maculopathy with periarterial sparing, whereas en face OCT segmented at the outer nuclear layer demonstrated florid cystoid macular edema. At 6-week follow-up, OCT demonstrated patchy areas of atrophic inner nuclear layer and spontaneous resolution of the cystoid macular edema. Optical coherence tomography angiography at the level of the deep capillary plexus illustrated remarkable flow reduction of the deep capillary plexus in mainly a perivenular distribution.

CONCLUSION

The authors report a case of a central retinal vein occlusion with mild retinal findings associated with a remarkable perivenular pattern of paracentral acute middle maculopathy with en face OCT. Follow-up OCT angiography demonstrated significant flow reduction of the deep capillary plexus in a perivenular pattern. The perivenular pattern of paracentral acute middle maculopathy lesions with en face OCT can be an important finding suggestive of a central retinal vein occlusion.

Cilioretinal artery hypoperfusion and its association with paracentral acute middle maculopathy

BACKGROUND/AIMS

To study the multimodal imaging findings of a large series of eyes with cilioretinal artery obstruction (CILRAO) and describe the systemic associations.

METHODS

Multicentre, retrospective chart review from 12 different retina clinics worldwide of eyes with CILRAO, defined as acute retinal whitening in the distribution of the cilioretinal artery, were identified. The clinical, systemic information and multimodal retinal imaging findings were collected and analysed.

RESULTS

A total of 53 eyes of 53 patients with CILRAO were included in the study. In 100% of eyes, fundus photography illustrated deep retinal whitening corresponding to the course of the cilioretinal artery. Twenty-eight patients (52.8%) presented with isolated CILRAO (baseline best-corrected visual acuity (BCVA) 20/50, final BCVA 20/25) associated with nocturnal hypotension, 23 patients (43.4%) with CILRAO secondary to central retinal vein occlusion (CRVO) (baseline BCVA 20/40, final BCVA 20/20) and two patients with CILRAO due to biopsy-proven giant cell arteritis (GCA) (baseline BCVA 20/175, final BCVA 20/75). With spectral domain optical coherence tomography (SD-OCT), a hyper-reflective band involving the inner nuclear layer (ie, paracentral acute middle maculopathy or PAMM) was noted in 51 eyes (28/28 eyes with isolated CILRAO and 23/23 eyes with CILRAO+CRVO) corresponding to the retinal whitening. In the two eyes with CILRAO+GCA, SD-OCT illustrated hyper-reflective ischaemia of both the middle and inner retina.

CONCLUSIONS

Isolated CILRAO and CILRAO secondary to CRVO are the result of hypoperfusion or insufficiency, rather than occlusion, of the cilioretinal artery and are associated with PAMM or selective infarction of the the inner nuclear layer. With GCA, there is complete occlusion of the cilioretinal artery producing ischaemia involving both the middle and inner retina associated with worse visual outcomes.

Human Parafoveal Capillary Vascular Anatomy and Connectivity Revealed by Optical Coherence Tomography Angiography

Purpose

To assess the connection among arterioles, venules, and capillaries in three retinal capillary plexuses using optical coherence tomography angiography (OCTA).

Methods

This was a prospective, cross-sectional, observational study including 20 eyes of 10 healthy subjects. En face and cross-sectional OCTA images were segmented to study the superficial (SCP), middle (MCP), and deep capillary plexuses (DCP). Using thin slabs and manual segmentation within the three plexuses, we examined the connections between the large-caliber superficial vessels within a 3 × 3 mm2 OCTA scan (arterioles and venules) and the smaller capillaries in each plexus.

Results

Twenty eyes of 10 healthy subjects (5 females; average age of 30.8 ± 6.3 years) were included in the analysis. We identified vascular interconnections linking the superficial arterioles and venules with capillaries in each plexus (SCP, MCP, and DCP). We found capillaries in the DCP crossed the horizontal raphe.

Conclusions

Our findings show that each of the three capillary plexuses in the parafovea has its own feeding arteriolar supply and draining venules, supporting a physiologic model in which each plexus controls its own oxygenated blood supply to match the metabolic needs of each distinct retinal neurovascular unit.