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Alexander Pinhas,1,2 Jorge S Andrade Romo,1 Giselle Lynch,1,3 Davis B Zhou,1,3 Maria V Castanos Toral,1 Phillip A Tenzel,1 Oscar Otero-Marquez,1 Shoshana Yakubova,1,4 Alexander Barash,1 David Della Rocca,1 Robert Della Rocca,1 Toco YP Chui,1 Richard B Rosen,1 Harsha S Reddy1 1Department of Ophthalmology, New York Eye and Ear Infirmary of Mount Sinai, New York, NY, USA; 2Department of Ophthalmology, State University of New York Downstate Medical Center, Brooklyn, NY, USA; 3Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, NY, USA; 4Department of Biology, Macaulay Honors College at City University of New York Queens College, Flushing, NY, USACorrespondence: Harsha S Reddy, Department of Ophthalmology, New York Eye and Ear Infirmary of Mount Sinai, 310 E 14th St, New York, NY, 10003, USA, Tel +1 212-979-4284, Fax +1 212-966-6295, Email hreddy@nyee.eduPurpose: Hemodynamic changes surrounding the optic nerve head are known to occur in thyroid-related orbitopathy (TRO). This pilot study explores the capillary and non-capillary peripapillary perfusion changes of the retina in TRO eyes without dysthyroid optic neuropathy (DON) using optical coherence tomography angiography (OCT-A).Methods: Non-capillary and capillary peripapillary perfusion densities were calculated using single 4.5 × 4.5mm en face “RPC layer” OCT-A scans of 8 TRO patients without DON (8 eyes, mean age 40.6 years, range 23– 69 years). Results were compared to a previously published dataset of 133 healthy controls (133 eyes, mean 41.5 years, range 11– 83 years). The strength of association was measured between OCT-A perfusion densities and clinical measures of TRO.Results: Non-capillary peripapillary perfusion density in TRO eyes was found to be significantly decreased compared to healthy controls (TRO group 15.4 ± 2.9% vs controls 21.5 ± 3.1%; p < 0.0001). Capillary peripapillary perfusion densities showed no significant difference (TRO group 42.5 ± 1.8% vs controls 42.5 ± 1.5%; p = 1.0). Clinical measures of disease did not correlate well with OCT-A perfusion densities (p> 0.05).Conclusion: These findings may represent decreased blood flow and subclinical ischemia to the optic nerve. We discuss possible pathogenic mechanisms of thyroid-related vasculopathy, including vessel wall thickening due to immunologically-induced media enlargement.Keywords: thyroid-related orbitopathy, optical coherence tomography angiography, peripapillary microvasculature, thyroid-related vasculopathy

We characterized the perceptual, functional, and structural abnormalities associated with retinal ischemia during a cotton wool spot episode and its sequelae. The border of the visually salient field anomaly mirrored the quantitatively measured relative scotoma. Results of resolution perimetry and high resolution imaging indicated that there was a substantial loss of retinal ganglion cells within the affected region. A disruption in retinal nerve fiber arrangement was found at the cotton wool spot and within the arcuate relative scotoma. The presence of the arcuate relative scotoma is consistent with the hypothesis of failed signal transmission along the axons that pass through the cotton wool spot. The different levels of loss associated with the arcuate and focal scotomas indicate different underlying pathologies. [ABSTRACT FROM AUTHOR]

Introduction: Vitreous cortex hyalocytes (VCH) are resident macrophage cells that provide immunosurveillance, respond to tissue injury and inflammation, and help maintain the transparency of the media. In this case report we demonstrate the use of en face optical coherence tomography (OCT) to image VCH in vivo in a patient presenting with PAMM secondary to antiphospholipid syndrome., Case Description: A 38-year-old female with no known medical history presented with complaints of visual disturbances in the right eye. OCT revealed hyperreflective bands in the IPL and INL nasal to the fovea. A diagnosis of PAMM was made. Work-up revealed elevated titers of antiphospholipid antibodies. En face OCT revealed a decline in the inflammatory activation over a seven-month period as evidenced by changes in VCH distribution and morphology., Conclusions: Our findings suggest that monitoring changes in the distribution and morphology of VCH could have a potential clinical utility for assessing disease severity, predicting recovery, and early recognition of treatment response in various inflammatory ocular pathologies such as PAMM., Competing Interests: Declaration of conflicting interestsThe author(s) declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: OOM, SA, LS, AP, TC have no conflicts of interest to declare. RB Rosen has the following commercial relationship(s) to declare: Optovue: Code C (Consultant); Astellas: Code C; (Consultant); Boehringer-Ingerheim:Code C (Consultant); NanoRetina: Code C; OD-OS: Code C; Opticology: Code I (Personal Financial Interest); Regeneron: Code C; Diopsys: Code C (Consultant); Guardion Health: Code C (Consultant); Bayer: Code C (Consultant); Genentech-Roche: Code C (Consultant).

Purpose: To report the impact of intravitreal anti-vascular endothelial growth factor (VEGF) therapy on a retinal capillary hemangioma (RCH) using clinical OCT angiography (OCT-A) in addition to standard imaging modalities., Observations: A 25-year-old male patient with Von Hippel-Lindau (VHL) disease presented with a history of bilateral RCH. No view was present in the right eye. Examination of the left eye revealed six peripheral RCH, the smallest of which was temporal to the macula with active exudation. This RCH was thought to be the source of cystoid macular edema (CME) involving the fovea, and therefore, the source of vision decline. 11 injections of 1.25mg of Bevacizumab EA across 14-month was given. Comparison of the pre- and post-treatment OCT-A at the temporal RCH showed a reduction of CME and regression of RCH., Conclusion: Anti-VEGF therapy appeared to stabilize the visual acuity and produce partial regression of RCH. It offers a safe option when visual acuity is threatened. OCT and OCT-A have the ability to document the impact of antiangiogenic therapy on RCH. 3D renderings of OCT-A offer enhanced sensitivity to recognition of structural and functional changes of RCH which may prove useful for monitoring treatment response., (© 2022 Published by Elsevier Inc.)

Introduction: Hyalocytes have been recognized as resident tissue macrophages of the vitreous body since the mid-19 th century. Despite this, knowledge about their origin, turnover, and dynamics is limited., Areas Covered: Historically, initial studies on the origin of hyalocytes used light and electron microscopy. Modern investigations across species including rodents and humans will be described. Novel imaging is now available to study human hyalocytes in vivo. The shared ontogeny with retinal microglia and their eventual interdependence as well as differences will be discussed., Expert Opinion: Owing to a common origin as myeloid cells, hyalocytes and retinal microglia have similarities, but hyalocytes appear to be distinct as resident macrophages of the vitreous body.

Introduction: Hyalocytes are sentinel macrophages residing within the posterior vitreous cortex anterior to the retinal inner limiting membrane (ILM). Following anomalous PVD and vitreoschisis, hyalocytes contribute to paucicellular (vitreo-macular traction syndrome, macular holes) and hypercellular (macular pucker, proliferative vitreo-retinopathy, proliferative diabetic vitreo-retinopathy) diseases., Areas Covered: Studies of human tissues employing dark-field, phase, and electron microscopy; immunohistochemistry; and in vivo imaging of human hyalocytes., Expert Opinion: Hyalocytes are important in early pathophysiology, stimulating cell migration and proliferation, as well as subsequent membrane contraction and vitreo-retinal traction. Targeting hyalocytes early could mitigate advanced disease. Ultimately, eliminating the role of vitreous and hyalocytes may prevent proliferative vitreo-retinal diseases entirely.

Purpose: Lafora disease is a genetic neurodegenerative metabolic disorder caused by insoluble polyglucosan aggregate accumulation throughout the central nervous system and body. The retina is an accessible neural tissue, which may offer alternative methods to assess neurological diseases quickly and noninvasively. In this way, noninvasive imaging may provide a means to characterize neurodegenerative disease, which enables earlier identification and diagnosis of disease and the ability to monitor disease progression. In this study, we sought to characterize the retina of individuals with Lafora disease using non-invasive retinal imaging., Methods: One eye of three individuals with genetically confirmed Lafora disease were imaged with optical coherence tomography (OCT) and adaptive optics scanning light ophthalmoscopy (AOSLO). When possible, OCT volume and line scans were acquired to assess total retinal thickness, ganglion cell-inner plexiform layer thickness, and outer nuclear layer + Henle fiber layer thickness. OCT angiography (OCTA) scans were acquired in one subject at the macula and optic nerve head (ONH). AOSLO was used to characterize the photoreceptor mosaic and examine the retinal nerve fiber layer (RNFL)., Results: Two subjects with previous seizure activity demonstrated reduced retinal thickness, while one subject with no apparent symptoms had normal retinal thickness. All other clinical measures, as well as parafoveal cone density, were within normal range. Nummular reflectivity at the level of the RNFL was observed using AOSLO in the macula and near the ONH in all three subjects., Conclusions: This multimodal retinal imaging approach allowed us to observe a number of retinal structural features in all three individuals. Most notably, AOSLO revealed nummular reflectivity within the inner retina of each subject. This phenotype has not been reported previously and may represent a characteristic change produced by the neurodegenerative process., Competing Interests: Mrs. Linderman is a consultant for OptoVue. Dr. Rosen has personal financial interest in Opticology and Guardion, and is a consultant for OptoVue, Boehringer-Ingelheim, Astellas, Genentech-Roche, NanoRetina, OD-OS, Regeneron, and Bayer. Dr. Vincent is a consultant for Adverum Biotechnologies Inc. Dr. Carroll receives financial support from AGTC and OptoVue, is a consultant for MeiraGTX, and has personal financial interest in Translational Imaging Innovations. Dr. Minassian is chief medical advisor to Taysha Gene Therapies. The following authors have no financial disclosures: H.H., J.A.C., E.N.W., R.M., P.S., T.Y.P., and E.J.P., (© 2021 The Authors.)

The molecular signaling cascades that regulate angiogenesis and microvascular remodeling are fundamental to normal development, healthy physiology, and pathologies such as inflammation and cancer. Yet quantifying such complex, fractally branching vascular patterns remains difficult. We review application of NASA's globally available, freely downloadable VESsel GENeration (VESGEN) Analysis software to numerous examples of 2D vascular trees, networks, and tree-network composites. Upon input of a binary vascular image, automated output includes informative vascular maps and quantification of parameters such as tortuosity, fractal dimension, vessel diameter, area, length, number, and branch point. Previous research has demonstrated that cytokines and therapeutics such as vascular endothelial growth factor, basic fibroblast growth factor (fibroblast growth factor-2), transforming growth factor-beta-1, and steroid triamcinolone acetonide specify unique "fingerprint" or "biomarker" vascular patterns that integrate dominant signaling with physiological response. In vivo experimental examples described here include vascular response to keratinocyte growth factor, a novel vessel tortuosity factor; angiogenic inhibition in humanized tumor xenografts by the anti-angiogenesis drug leronlimab; intestinal vascular inflammation with probiotic protection by Saccharomyces boulardii, and a workflow programming of vascular architecture for 3D bioprinting of regenerative tissues from 2D images. Microvascular remodeling in the human retina is described for astronaut risks in microgravity, vessel tortuosity in diabetic retinopathy, and venous occlusive disease., (© 2021 S. Karger AG, Basel.)

Purpose: The purpose of this study was to investigate the effect of device and scan size on quantitative optical coherence tomography angiography (OCT-A) metrics., Methods: The 3 × 3 mm scans from Optovue AngioVue and Zeiss AngioPlex systems were included for 18 eyes of 18 subjects without ocular pathology. The foveal avascular zone (FAZ) was segmented manually by two observers, from which estimates of FAZ area (using both the nominal image scale and the axial length corrected image scale) and acircularity were derived. Three scan sizes (3 mm, 6 mm HD, and 8 mm) from the AngioVue system were included for 15 eyes of 15 subjects without ocular pathology. For each subject, larger image sizes were resized to the same resolution as 3 × 3 mm scans, aligned, then cropped to a common area. FAZ area, FAZ acircularity, average and total parafoveal intercapillary area, vessel density, and vessel end points were computed., Results: Between the devices used here, there were no significant differences in FAZ acircularity ( P = 0.88) or FAZ area using scaled ( P = 0.11) or unscaled images ( P = 0.069). Although there was no significant difference in FAZ area across scan sizes ( P = 0.30), vessel morphometry metrics were all significantly influenced by scan size., Conclusions: The scan devices and sizes used here do not affect FAZ area measures derived from manual segmentations. In contrast, vessel morphometry metrics are affected by scan size. As individual differences in axial length induce differences in absolute scan size, extreme care should be taken when interpreting metrics of vessel morphometry, both between and within OCT-A devices., Translational Relevance: A better characterization of the confounds surrounding OCT-A retinal vasculature metrics can lead to improved application of these metrics as biomarkers for retinal and systemic diseases., Competing Interests: Disclosure: J.A. Kraker, None; B.S. Omoba, None; J.A. Cava, None; T. Gilat Schmidt, GE Healthcare (F); T.Y. Chui, None; R.B. Rosen, Advanced Cellular Technologies (C), Carl Zeiss Meditech (C), Clarity, NanoRetina (C), OD-OS (C), Optovue (C), and Regeneron (C), Opticology (I); J.E. Kim, Notal Vision (F), Optos (F), Adverum (C), Allergan (C), Alimera Science (C), Clearside (C), Gemini (C), Genentech (C), Kodiak (C), Notal Vision (C), and Novartis (C); J. Carroll, Optovue (F), AGTC (F), MeiraGTx (F), MeiraGTx (C), and Translational Imaging Innovations (I); R.E. Linderman, Optovue (C), (Copyright 2020 The Authors.)

Objectives: To examine interocular asymmetry of foveal avascular zone (FAZ) and parafoveal capillary density metrics in sickle cell retinopathy (SCR) using optical coherence tomography angiography (OCT-A)., Methods: This cross-sectional, retrospective study evaluated SCR patients and unaffected controls who underwent 3x3mm macular OCT-A imaging using a spectral domain-OCT system. FAZ (area, perimeter, and acircularity index) and parafoveal capillary density metrics were computed for both eyes of each participant. In unaffected controls, interocular difference in FAZ and parafoveal capillary density metrics were evaluated using Bland-Altman plots. SCR patients with interocular difference outside the upper 97.5% and lower 2.5% limits of agreement from controls were defined as having interocular asymmetry. Area under receiver operating characteristic curve (AROC) was also performed to determine the ability of the absolute interocular difference to differentiate between subjects with SCR-including non-proliferative SCR (NP-SCR) and proliferative SCR (P-SCR)-and unaffected controls., Results: Thirty-one patients with SCR (21 NP-SCR and 10 P-SCR) and 14 race-matched and age-matched controls were included for analysis. Interocular asymmetry was seen for all FAZ and parafoveal capillary density metrics in NP-SCR and P-SCR subjects. SCR subjects showed greater disease severity in the left-eye for FAZ and parafoveal capillary density metrics., Conclusions: NP-SCR and P-SCR patients demonstrated quantifiable interocular asymmetry in FAZ and parafoveal capillary density metrics compared to unaffected subjects, with left-eye predominance in disease severity., Competing Interests: AWS: Allergan (Consultant), Novartis (Consultant), Optos (Material Support). RBR: Optovue (Consultant), Boehringer-Ingelheim (Consultant), Astellas (Consultant), Genentech-Roche (Consultant), NanoRetina (Consultant), OD-OS (Consultant), Regeneron (Consultant), Bayer (Consultant), Diopsys (Consultant), Teva (Consultant), Opticology, (Personal Financial Interest), Guardion (Personal Financial Interest), GlaucoHealth (Personal Financial Interest). JC: Optovue (Financial Support), Translational Imaging Innovations (Personal Financial Interest). REL: Optovue (Consultant). These competing interests do not alter our adherence to PLOS ONE policies on sharing data and materials.

Purpose: To assess the frequency and impact of abnormal foveal avascular zone (FAZ) topography (i.e., a fragmented FAZ) on visual acuity and foveal anatomic features., Design: Prospective, cross-sectional study from March 2018 through July 2019., Participants: Two-hundred fifty participants were screened from a normative OCT angiography database. Of those, 12 participants were found to have at least 1 eye with a fragmented FAZ. Eight returned for follow-up imaging, along with an additional 3 participants with ocular disease (amblyopia, autosomal recessive bestrophinopathy, premature birth) having a similar FAZ phenotype., Methods: Follow-up OCT imaging and monocular best-corrected visual acuity (BCVA) were performed for these 11 participants. Twenty-four participants with a clearly defined FAZ were recruited for comparison. A normative database was created measuring parafoveal intercapillary area (PICA) to determine if an FAZ was fragmented., Main Outcome Measures: Monocular BCVA, foveal pit depth, foveal pit area, PICA, outer nuclear layer thickness, foveal inner retinal area, and peak cone density., Results: The frequency of a fragmented FAZ was 4.8% of individuals (12 of 250) or 3.6% of eyes (18 of 500 eyes). A significant difference was found between the control eyes and eyes with fragmented FAZs for foveal pit depth, pit area, and total PICA (P < 0.001, P = 0.002, and P < 0.001, respectively). The presence of a fragmented FAZ did not affect visual acuity., Conclusions: The presence of a fragmented FAZ seems not to be a rare phenotype in individuals with normal vision. The presence of altered FAZ topography in patients with retinal or systemic disease could negatively impact the accuracy and sensitivity of biomarkers dependent on FAZ identification., (Copyright © 2019 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Background/aims: To assess foveal avascular zone (FAZ) morphology and parafoveal capillary perfusion in patients with various stages of sickle cell retinopathy (SCR) using optical coherence tomography angiography (OCT-A)., Methods: This is a multi-institutional retrospective study of patients with various stages of SCR compared with healthy controls. Parafoveal OCT-A images obtained using a commercial spectral domain-OCT system were reviewed. Foveal-centred 3×3 mm full vascular slab OCT-As were used for image processing and data analysis. FAZ area, perimeter, and acircularity index were determined on the OCT-A image after manual delineation of the FAZ border. Quadrant-based parafoveal capillary density and per cent area deviating from normal distribution were also measured., Results: Fifty-two patients with SCR (33 non-proliferative and 19 proliferative) and 20 age and race-matched healthy controls were included. One randomly selected eye per study participant was analysed. FAZ perimeter and acircularity index were significantly greater in SCR eyes when compared with the controls. While parafoveal capillary density was significantly lower, per cent area deviated from normal distribution was significantly higher in SCR eyes than that of the control. However, no statistically significant difference between the two SCR stages was observed. In quadrant-based analysis, the temporal quadrant showed greater parafoveal capillary dropout due to SCR, with the most profound effect in patients with proliferative SCR., Conclusions: Abnormal FAZ morphology and altered parafoveal capillary perfusion were found in patients with SCR. Our customised OCT-A image analysis method uniquely highlights significant quantitative alterations in perfusion density mapping in a qualitative display, with minimal obscuration of OCT-A image detail., Competing Interests: Competing interests: RBR: Optovue: Code C (Consultant); Boehringer Ingelheim: Code C (Consultant); Astellas: Code C; Genentech-Roche: Code C; NanoRetina: Code C; OD-OS: Code C; Opticology: Code I (Personal Financial Interest); Guardion: Code I (Personal Financial Interest); GlaucoHealth: Code I (Personal Financial Interest); Regeneron: Code C; Bayer: Code C; Diopsys: Code C (Consultant); Teva: Code C (Consultant). JC: Optovue: Code F (Financial Support). REL: Optovue: Code C (Consultant)., (© Author(s) (or their employer(s)) 2020. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ.)

Purpose: To present a method for age-matched deviation mapping in the assessment of disease-related changes to the radial peripapillary capillaries (RPCs)., Methods: We reviewed 4.5x4.5mm en face peripapillary OCT-A scans of 133 healthy control eyes (133 subjects, mean 41.5 yrs, range 11-82 yrs) and 4 eyes with distinct retinal pathologies, obtained using spectral-domain optical coherence tomography angiography. Statistical analysis was performed to evaluate the impact of age on RPC perfusion densities. RPC density group mean and standard deviation maps were generated for each decade of life. Deviation maps were created for the diseased eyes based on these maps. Large peripapillary vessel (LPV; noncapillary vessel) perfusion density was also studied for impact of age., Results: Average healthy RPC density was 42.5±1.47%. ANOVA and pairwise Tukey-Kramer tests showed that RPC density in the ≥60yr group was significantly lower compared to RPC density in all younger decades of life (p<0.01). Average healthy LPV density was 21.5±3.07%. Linear regression models indicated that LPV density decreased with age, however ANOVA and pairwise Tukey-Kramer tests did not reach statistical significance. Deviation mapping enabled us to quantitatively and visually elucidate the significance of RPC density changes in disease., Conclusions: It is important to consider changes that occur with aging when analyzing RPC and LPV density changes in disease. RPC density, coupled with age-matched deviation mapping techniques, represents a potentially clinically useful method in detecting changes to peripapillary perfusion in disease., Competing Interests: Dr. Carroll receives financial support from Optovue. Dr. Rosen is a paid consultant for Optovue, Advanced Cellular Technologies, Carl Zeiss Meditech, Clarity, NanoRetina, OD-OS, and Regeneron. Dr. Rosen has personal financial interest in Opticology. These funders have no role in this study’s design, including the collection, analysis, and interpretation of data, writing of the paper, or decision to submit for publication. To the best of our knowledge, these funders have not served and currently do not serve on the editorial board of your journal. These funders have not acted as an expert witness in relevant legal proceedings. This does not alter our adherence to PLOS ONE policies on sharing data and materials.

Importance: This study used optical coherence tomographic angiography to assess for impaired blood flow in myopic eyes with or without open-angle glaucoma., Objective: To compare the peripapillary perfused capillary density (PCD) between eyes with and without glaucoma., Design, Setting, and Participants: In this cross-sectional study at a tertiary glaucoma referral practice, we recruited patients with myopic eyes of spherical equivalent of more than -3.0 diopters with and without open-angle glaucoma, patients with nonmyopic eyes with glaucoma, and patients with no disease from February 2016 to October 2016. We obtained 4.5 × 4.5-mm optical coherence tomographic angiography images of the optic nerve head and calculated PCD as the ratio of pixels associated with capillaries to the number of pixels in the region of interest after large blood vessel removal. Both eyes of each patient were used in the analysis. Continuous variables were assessed by analysis of variance and Tukey tests. A marginal model of generalized estimating equations was performed to adjust for confounding factors and intraclass correlations., Main Outcomes and Measures: Mean PCD., Results: We matched 87 patients with myopic eyes with glaucoma (of whom 39 [45%] were women), 17 with myopic eyes without glaucoma (of whom 10 [59%] were women), and 93 with non-myopic eyes with glaucoma (of whom 55 [59%] were women) for visual field defects and included 51 control participants (or whom 38 [75%] were women). Mean (SD) ages were 67.5 (12.0) years for patients with myopia and glaucoma, 48.2 (19.0) years for those with myopia without glaucoma, 67.3 (11.0) years for those with glaucoma without myopia, and 64.7 (8.9) years in control participants. Global PCD demonstrated a progressive decrease from the control group (mean [SD], 41.0 [4.2]) to those with myopia without glaucoma (38.4 [5.8]) to those with glaucoma without myopia (31.9 [7.5]) to those with both (28.2 [6.0]; all P < .001). The mean difference in global PCD between the 3 groups and control group, adjusted for age and axial length, was greatest in those with myopia and glaucoma (-11.1; 95% CI, -14.0 to -8.1; P < .001), followed by those with glaucoma without myopia (-8.6; 95% CI, -10.9 to -6.3; P < .001) and those with myopia without glaucoma (-2.8; 95% CI, -6.9 to 1.2; P = .17). No interaction was found between glaucoma and myopia., Conclusions and Relevance: These findings demonstrate peripapillary microvascular attenuation to a greater extent in open-angle glaucoma than myopia. The cross-sectional design means we cannot determine if this association is a cause and/or is associated with other confounding factors.

Purpose: To compare the peripapillary perfused capillary density (PCD) among eyes with exfoliation syndrome (XFS), exfoliation glaucoma (XFG), primary open-angle glaucoma (POAG), and controls., Design: Observational, cross-sectional study., Methods: Optical coherence tomography angiography (OCTA) images (4.5×4.5 mm) of the optic nerve head were obtained using a commercial spectral domain OCTA system (AngioVue Avanti RTVue-XR, OptoVue, Fremont, CA). Two concentric circles with 1.95-mm (inner) and 3.45-mm (outer) diameters were placed manually, producing an annulus of width 0.75 mm centered at the optic disc. PCD was calculated as the ratio of pixels associated with capillaries to the pixels in the annulus after large blood vessel removal. Continuous variables were assessed by analysis of variance and Tukey honest significant difference (HSD) test. Multiple linear regression analysis was performed to adjust for confounding factors., Results: Forty-three XFG eyes, 31 POAG eyes matched for visual field mean deviation, 33 XFS eyes, and 45 control eyes were analyzed. PCD demonstrated a progressive decrease from controls to XFS to POAG to XFG. Pairwise comparisons revealed significant differences in PCD between each pair of groups (all P<0.01) except for PCD between XFS and POAG (P = 0.08). A multivariable model adjusting for age and stage showed a more significant decrease in PCD in XFG compared with POAG (P = 0.001)., Conclusions: PCD was more significantly decreased in XFG compared with POAG eyes and in XFS compared with control eyes. OCTA provides the first quantitative evidence of the microvascular disturbance that accompanies XFS., (Copyright 2017 Asia-Pacific Academy of Ophthalmology.)

Purpose: Both non-arteritic anterior ischemic optic neuropathy (NAION) and primary open-angle glaucoma (POAG) damage retinal ganglion cell axons, which are perfused by the radial peripapillary capillaries. To evaluate the pattern of ischemia, we compared peripapillary capillary density (PCD) in NAION eyes to POAG eyes matched for visual field mean deviation and retinal nerve fiber layer thickness., Methods: 31 chronic NAION (>6 months after the acute event) and unaffected fellow eyes (31 subjects), 42 moderate and severe POAG eyes (27 subjects), and 77 control eyes (46 healthy subjects) were imaged with a commercial optical coherence tomography angiography system (AngioVue, Avanti RTVue-XR, Optovue, CA) at two academic institutions. Two concentric circles of diameters 1.95mm (inner) and 3.45mm (outer) were manually placed on images centered on the optic nerve head, producing an annular region-of-interest. Image analysis with major vessel removal was performed using a custom program. Whole-image, whole-annulus, and sectoral PCDs were measured., Results: Whole-image and whole-annulus PCDs in NAION and moderate and severe POAG eyes were significantly decreased compared to unaffected fellow eyes and control eyes (all P<0.001). Superior and temporal PCD values were affected more than other sectors in both NAION and POAG groups compared to control group. Whole-image and whole-annulus PCDs were not statistically different between NAION and POAG eyes (both P = 0.99). However, of all peripapillary sectors, the inferior sector PCD value was less affected in POAG eyes compared to NAION eyes (P = 0.001). Univariate analysis results also revealed a significant positive correlation between superior and inferior PCDs and corresponding RNFL thicknesses. The inferior sector correlation was greater in POAG than NAION eyes., Conclusion: While the whole PCD values were not different in chronic NAION and POAG, the greater correlation of inferior PCD with corresponding RNFL sectors in POAG compared to NAION suggests greater susceptibility of the inferior radial peripapillary capillary in the pathogenesis of POAG.

Large individual differences in cone densities occur even in healthy, young adults with low refractive error. We investigated whether cone density follows a simple model that some individuals have more cones, or whether individuals differ in both number and distribution of cones. We quantified cones in the eyes of 36 healthy young adults with low refractive error using a custom adaptive optics scanning laser ophthalmoscope. The average cone density in the temporal meridian was, for the mean±SD, 43,216±6039, 27,466±3496, 14,996±1563, and 12,207±1278cones/mm 2 for 270, 630, 1480, and 2070μm from the foveal center. Cone densities at 630μm retinal eccentricity were uncorrelated to those at 2070μm, ruling out models with a constant or proportional relation of cone density to eccentricity. Subjects with high central macula cone densities had low peripheral cone densities. The cone density ratio (2070:630μm) was negatively correlated with cone density at 630μm, consistent with variations in the proportion of peripheral cones migrating towards the center. We modelled the total cones within a central radius of 7deg, using the temporal data and our published cone densities for temporal, nasal, superior, and inferior meridians. We computed an average of 221,000 cones. The coefficient of variation was 0.0767 for total cones, but higher for samples near the fovea. Individual differences occur both in total cones and other developmental factors related to cone distribution., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Objectives: To assess the effect of image registration and averaging on the visualization and quantification of the radial peripapillary capillary (RPC) network on optical coherence tomography angiography (OCTA)., Methods: Twenty-two healthy controls were imaged with a commercial OCTA system (AngioVue, Optovue, Inc.). Ten 10x10° scans of the optic disc were obtained, and the most superficial layer (50-μm slab extending from the inner limiting membrane) was extracted for analysis. Rigid registration was achieved using ImageJ, and averaging of each 2 to 10 frames was performed in five ~2x2° regions of interest (ROI) located 1° from the optic disc margin. The ROI were automatically skeletonized. Signal-to-noise ratio (SNR), number of endpoints and mean capillary length from the skeleton, capillary density, and mean intercapillary distance (ICD) were measured for the reference and each averaged ROI. Repeated measures analysis of variance was used to assess statistical significance. Three patients with primary open angle glaucoma were also imaged to compare RPC density to controls., Results: Qualitatively, vessels appeared smoother and closer to histologic descriptions with increasing number of averaged frames. Quantitatively, number of endpoints decreased by 51%, and SNR, mean capillary length, capillary density, and ICD increased by 44%, 91%, 11%, and 4.5% from single frame to 10-frame averaged, respectively. The 10-frame averaged images from the glaucomatous eyes revealed decreased density correlating to visual field defects and retinal nerve fiber layer thinning., Conclusions: OCTA image registration and averaging is a viable and accessible method to enhance the visualization of RPCs, with significant improvements in image quality and RPC quantitative parameters. With this technique, we will be able to non-invasively and reliably study RPC involvement in diseases such as glaucoma., Competing Interests: The authors of this manuscript have the following competing interests: Joseph Carroll: Optovue (Use of Equipment); Richard B Rosen: Clarity (Consultant), Opticology (Personal Financial Interest), OD-OS (Consultant), Allergan (Consultant), Carl Zeiss Meditech (Consultant), Optovue (Consultant), Advanced Cellular Technologies (Consultant), NanoRetina (Consultant), Regeneron (Consultant), Genentech (Financial Support). This does not alter the authors' adherence to PLOS ONE policies on sharing data and materials.

Purpose: Small artery and arteriolar walls thicken due to elevated blood pressure. Vascular wall thickness show a correlation with hypertensive subject history and risk for stroke and cardiovascular events., Methods: The inner and outer diameter of retinal arterioles from less than 10 to over 150 μm were measured using a multiply scattered light adaptive optics scanning laser ophthalmoscope (AOSLO). These measurements were made on three populations, one with habitual blood pressures less than 100/70 mm Hg, one with normal blood pressures without medication, and one with managed essential hypertension., Results: The wall to lumen ratio was largest for the smallest arterioles for all three populations. Data from the hypotensive group had a linear relationship between outer and inner diameters ( r 2 = 0.99) suggesting a similar wall structure in individuals prior to elevated blood pressures. Hypertensive subjects fell below the 95% confidence limits for the hypotensive relationship and had larger wall to lumen ratios and the normotensive group results fell between the other two groups., Conclusion: High-resolution retinal imaging of subjects with essential hypertension showed a significant decrease in vessel inner diameter for a given outer diameter, and increases in wall to lumen ratio and wall cross-sectional areas over the entire range of vessel diameters and suggests that correcting for vessel size may improve the ability to identify significant vascular changes., Translational Relevance: High-resolution imaging allows precise measurement of vasculature and by comparing results across risk populations may allow improved identification of individuals undergoing hypertensive arterial wall remodeling.

Purpose: To compare perfused peripapillary capillary density in primary open-angle glaucoma (POAG), normal-tension glaucoma (NTG), and normal patients using optical coherence tomography angiography (OCT-A)., Methods: A retrospective review of POAG, NTG, and normal patients imaged with OCT-A was performed. En face OCT angiograms identifying peripapillary vessels were obtained using a spectral-domain OCT system (Avanti RTVue-XR). A custom image analysis approach identified perfused peripapillary capillaries, quantified perfused capillary density (PCD), and generated color-coded PCD maps for 3.5- and 4.5-mm-diameter scans. We compared PCD values, PCD maps, standard automated perimetry (Humphrey visual field [HVF]) parameters, and OCT retinal nerve fiber layer (RNFL) thickness analyses across all groups., Results: Forty POAG, 26 NTG, and 26 normal patients were included. Annular PCD in POAG (34.24 ± 6.76%) and NTG (37.75 ± 3.52%) patients was significantly decreased compared to normal patients (42.99 ± 1.81%) in 4.5-mm scans (P < 0.01 and P < 0.01, respectively). Similar trends and statistical significances were seen in 3.5-mm scans. Linear regression analysis resulted in moderate correlations between annular PCD values and other glaucomatous parameters. Pearson coefficients comparing annular PCD from 4.5-mm scans in POAG and NTG groups to HVF mean deviation, HVF pattern standard deviation, and average RNFL thickness all showed statistical significance (P < 0.05). Color maps showed that POAG and NTG patients had a reduction of perfused capillaries that progressed in size when comparing early, moderate, and severe glaucoma groups., Conclusions: Optical coherence tomography angiography can uniquely identify changes in peripapillary PCD in glaucoma patients. Optical coherence tomography angiography may offer insights into the pathophysiology of glaucomatous damage and risk factors for disease progression.

Purpose: To compare the use of optical coherence tomography angiography (OCTA) and adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA) for characterizing the foveal microvasculature in healthy and vasculopathic eyes., Methods: Four healthy controls and 11 vasculopathic patients (4 diabetic retinopathy, 4 retinal vein occlusion, and 3 sickle cell retinopathy) were imaged with OCTA and AOSLO FA. Foveal perfusion maps were semiautomatically skeletonized for quantitative analysis, which included foveal avascular zone (FAZ) metrics (area, perimeter, acircularity index) and vessel density in three concentric annular regions of interest. On each set of OCTA and AOSLO FA images, matching vessel segments were used for lumen diameter measurement. Qualitative image comparisons were performed by visual identification of microaneurysms, vessel loops, leakage, and vessel segments., Results: Adaptive optics scanning light ophthalmoscope FA and OCTA showed no statistically significant differences in FAZ perimeter, acircularity index, and vessel densities. Foveal avascular zone area, however, showed a small but statistically significant difference of 1.8% (P = 0.004). Lumen diameter was significantly larger on OCTA (mean difference 5.7 μm, P < 0.001). Microaneurysms, fine structure of vessel loops, leakage, and some vessel segments were visible on AOSLO FA but not OCTA, while blood vessels obscured by leakage were visible only on OCTA., Conclusions: Optical coherence tomography angiography is comparable to AOSLO FA at imaging the foveal microvasculature except for differences in FAZ area, lumen diameter, and some qualitative features. These results, together with its ease of use, short acquisition time, and avoidance of potentially phototoxic blue light, support OCTA as a tool for monitoring ocular pathology and detecting early disease.

Purpose: To characterise longitudinal changes in the retinal microvasculature of type 2 diabetes mellitus (T2DM) as exemplified in a patient with proliferative diabetic retinopathy (PDR) using an adaptive optics scanning light ophthalmoscope (AOSLO)., Methods: A 35-year-old T2DM patient with PDR treated with scatter pan-retinal photocoagulation at the inferior retina 1 day prior to initial AOSLO imaging along with a 24-year-old healthy control were imaged in this study. AOSLO vascular structural and perfusion maps were acquired at four visits over a 20-week period. Capillary diameter and microaneurysm area changes were measured on the AOSLO structural maps. Imaging repeatability was established using longitudinal imaging of microvasculature in the healthy control., Results: Capillary occlusion and recanalisation, capillary dilatation, resolution of local retinal haemorrhage, capillary hairpin formation, capillary bend formation, microaneurysm formation, progression and regression were documented over time in a region 2° superior to the fovea in the PDR patient. An identical microvascular network with same capillary diameter was observed in the control subject over time., Conclusions: High-resolution serial AOSLO imaging enables in vivo observation of vasculopathic changes seen in diabetes mellitus. The implications of this methodology are significant, providing the opportunity for studying the dynamics of the pathological process, as well as the possibility of identifying highly sensitive and non-invasive biomarkers of end organ damage and response to treatment., (© 2016 The Authors Ophthalmic & Physiological Optics © 2016 The College of Optometrists.)

Purpose: To characterize the effects of intraframe distortion due to involuntary eye motion on measures of cone mosaic geometry derived from adaptive optics scanning light ophthalmoscope (AOSLO) images., Methods: We acquired AOSLO image sequences from 20 subjects at 1.0, 2.0, and 5.0° temporal from fixation. An expert grader manually selected 10 minimally distorted reference frames from each 150-frame sequence for subsequent registration. Cone mosaic geometry was measured in all registered images ( n = 600) using multiple metrics, and the repeatability of these metrics was used to assess the impact of the distortions from each reference frame. In nine additional subjects, we compared AOSLO-derived measurements to those from adaptive optics (AO)-fundus images, which do not contain system-imposed intraframe distortions., Results: We observed substantial variation across subjects in the repeatability of density (1.2%-8.7%), inter-cell distance (0.8%-4.6%), percentage of six-sided Voronoi cells (0.8%-10.6%), and Voronoi cell area regularity (VCAR) (1.2%-13.2%). The average of all metrics extracted from AOSLO images (with the exception of VCAR) was not significantly different than those derived from AO-fundus images, though there was variability between individual images., Conclusions: Our data demonstrate that the intraframe distortion found in AOSLO images can affect the accuracy and repeatability of cone mosaic metrics. It may be possible to use multiple images from the same retinal area to approximate a "distortionless" image, though more work is needed to evaluate the feasibility of this approach., Translational Relevance: Even in subjects with good fixation, images from AOSLOs contain intraframe distortions due to eye motion during scanning. The existence of these artifacts emphasizes the need for caution when interpreting results derived from scanning instruments.

Purpose: Eyes fellow to nonischemic central retinal vein occlusion (CRVO) were examined for abnormalities, which might explain their increased risk for future occlusion, using adaptive optics scanning light ophthalmoscope fluorescein angiography., Methods: Adaptive optics scanning light ophthalmoscope fluorescein angiography foveal microvascular densities were calculated. Nonperfused capillaries adjacent to the foveal avascular zone were identified. Spectral domain optical coherence tomography, ultrawide field fluorescein angiographies, and microperimetry were also performed., Results: Ten fellow eyes of nine nonischemic CRVO and 1 nonischemic hemi-CRVO subjects and four affected eyes of three nonischemic CRVO and one nonischemic hemi-CRVO subjects were imaged. Ninety percent of fellow eyes and 100% of affected eyes demonstrated at least 1 nonperfused capillary compared with 31% of healthy eyes. Fellow eye microvascular density (35 ± 3.6 mm(-1)) was significantly higher than that of affected eyes (25 ± 5.2 mm(-1)) and significantly lower than that of healthy eyes (42 ± 4.2 mm(-1)). Compared with healthy controls, spectral domain optical coherence tomography thicknesses showed no significant difference, whereas microperimetry and 2/9 ultrawide field fluorescein angiography revealed abnormalities in fellow eyes., Conclusion: Fellow eye changes detectable on adaptive optics scanning light ophthalmoscope fluorescein angiography reflect subclinical pathology difficult to detect using conventional imaging technologies. These changes may help elucidate the pathogenesis of nonischemic CRVO and help identify eyes at increased risk of future occlusion.

Purpose: High-resolution images of glaucomatous damage to the retinal nerve fiber layer (RNFL) were obtained with an adaptive optics-scanning light ophthalmoscope (AO-SLO) and used as a basis for comparisons between en face slab images and thickness maps derived from optical coherence tomography (OCT) scans., Methods: Wide-field (9 × 12 mm) cube scans were obtained with swept-source OCT (DRI-OCT) from six eyes of six patients. All eyes had a deep defect near fixation as seen on a 10-2 visual field test. Optical coherence tomography en face images, based on the average reflectance intensity, were generated (ATL 3D-Suite) from 52-μm slabs just below the vitreal border of the inner limiting membrane. The RNFL thickness maps were generated from the same OCT data. Both were compared with the AO-SLO peripapillary images that were previously obtained., Results: On AO-SLO images, three eyes showed small regions of preserved and/or missing RNFL bundles within the affected region. Details in these regions were seen on the OCT en face images but not on the RNFL thickness maps. In addition, in the healthier hemi-retinas of two eyes, there were darker, arcuate-shaped regions on en face images that corresponded to abnormalities seen on AO-SLO. These were not seen on RNFL thickness maps., Conclusions: Details of local glaucomatous damage, missing or easily overlooked on traditional OCT RNFL thickness analysis used in clinical OCT reports, were seen on OCT en face images based on the average reflectance intensity. While more work is needed, it is likely that en face slab imaging has a role in the clinical management of glaucoma.

Purpose: We generated a model of eye growth and tested it against an eye known to develop abnormally, one with a history of retinopathy of prematurity (ROP)., Methods: We reviewed extant magnetic resonance images (MRIs) from term and preterm-born patients for suitable images (n = 129). We binned subjects for analysis based upon postmenstrual age at birth (in weeks) and ROP history ("Term" ≥ 37, "Premature" ≤ 32 with no ROP, "ROP" ≤ 32 with ROP). We measured the axial positions and curvatures of the cornea, anterior and posterior lens, and inner retinal surface. We fit anterior chamber depth (ACD), posterior segment depth (PSD), axial length (AL), and corneal and lenticular curvatures with logistic growth curves that we then evaluated for significant differences. We also measured the length of rays from the centroid to the surface of the eye at 5° intervals, and described the length versus age relationship of each ray, L(ray)(x), using the same logistic growth curve. We determined the rate of ray elongation, E(ray)(x), from L(ray)dy/dx. Then, we estimated the scleral growth that accounted for E(ray)(x), G(x), at every age and position., Results: Relative to Term, development of ACD, PSD, AL, and corneal and lenticular curvatures was delayed in ROP eyes, but not Premature eyes. In Term infants, G(x) was fast and predominantly equatorial; in age-matched ROP eyes, maximal G(x) was offset by approximately 90°., Conclusions: We produced a model of normal eye growth in term-born subjects. Relative to normal, the ROP eye is characterized by delayed, abnormal growth.

Purpose: To improve our understanding of glaucomatous damage as seen on circumpapillary disc scans obtained with frequency-domain optical coherence tomography (fdOCT), fdOCT scans were compared to images of the peripapillary retinal nerve fiber (RNF) bundles obtained with an adaptive optics-scanning light ophthalmoscope (AO-SLO)., Methods: The AO-SLO images and fdOCT scans were obtained on 6 eyes of 6 patients with deep arcuate defects (5 points ≤-15 db) on 10-2 visual fields. The AO-SLO images were montaged and aligned with the fdOCT images to compare the RNF bundles seen with AO-SLO to the RNF layer thickness measured with fdOCT., Results: All 6 eyes had an abnormally thin (1% confidence limit) RNF layer (RNFL) on fdOCT and abnormal (hyporeflective) regions of RNF bundles on AO-SLO in corresponding regions. However, regions of abnormal, but equal, RNFL thickness on fdOCT scans varied in appearance on AO-SLO images. These regions could be largely devoid of RNF bundles (5 eyes), have abnormal-appearing bundles of lower contrast (6 eyes), or have isolated areas with a few relatively normal-appearing bundles (2 eyes). There also were local variations in reflectivity of the fdOCT RNFL that corresponded to the variations in AO-SLO RNF bundle appearance., Conclusions: Relatively similar 10-2 defects with similar fdOCT RNFL thickness profiles can have very different degrees of RNF bundle damage as seen on fdOCT and AO-SLO., Translational Relevance: While the results point to limitations of fdOCT RNFL thickness as typically analyzed, they also illustrate the potential for improving fdOCT by attending to variations in local intensity.

Purpose: To better understand the nature of glaucomatous damage of the macula, especially the structural changes seen between relatively healthy and clearly abnormal (AB) retinal regions, using an adaptive optics scanning light ophthalmoscope (AO-SLO)., Methods: Adaptive optics SLO images and optical coherence tomography (OCT) vertical line scans were obtained on one eye of seven glaucoma patients, with relatively deep local arcuate defects on the 10-2 visual field test in one (six eyes) or both hemifields (one eye). Based on the OCT images, the retinal nerve fiber (RNF) layer was divided into two regions: (1) within normal limits (WNL), relative RNF layer thickness within mean control values ±2 SD; and (2) AB, relative thickness less than -2 SD value., Results: As seen on AO-SLO, the pattern of AB RNF bundles near the border of the WNL and AB regions differed across eyes. There were normal-appearing bundles in the WNL region of all eyes and AB-appearing bundles near the border with the AB region. This region with AB bundles ranged in extent from a few bundles to the entire AB region in the case of one eye. All other eyes had a large AB region without bundles. However, in two of these eyes, a few bundles were seen within this region of otherwise missing bundles., Conclusions: The AO-SLO images revealed details of glaucomatous damage that are difficult, if not impossible, to see with current OCT technology. Adaptive optics SLO may prove useful in following progression in clinical trials, or in disease management, if AO-SLO becomes widely available and easy to use., (Copyright 2015 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To analyze the foveal microvasculature of young healthy eyes and older vasculopathic eyes, imaged using in vivo adaptive optics scanning light ophthalmoscope fluorescein angiography (AOSLO FA)., Methods: AOSLO FA imaging of the superficial retinal microvasculature within an 800-μm radius from the foveal center was performed using simultaneous confocal infrared (IR) reflectance (790 nm) and fluorescence (488 nm) channels. Corresponding IR structural and FA perfusion maps were compared with each other to identify nonperfused capillaries adjacent to the foveal avascular zone. Microvascular densities were calculated from skeletonized FA perfusion maps., Results: Sixteen healthy adults (26 eyes; mean age 25 years, range, 21-29) and six patients with a retinal vasculopathy (six eyes; mean age 55 years, range, 44-70) were imaged. At least one nonperfused capillary was observed in five of the 16 healthy nonfellow eyes and in four of the six vasculopathic eyes. Compared with healthy eyes, capillary nonperfusion in the vasculopathic eyes was more extensive. Microvascular density of the 16 healthy nonfellow eyes was 42.0 ± 4.2 mm(-1) (range, 33-50 mm(-1)). All six vasculopathic eyes had decreased microvascular densities., Conclusions: AOSLO FA provides an in vivo method for estimating foveal microvascular density and reveals occult nonperfused retinal capillaries. Nonperfused capillaries in healthy young adults may represent a normal variation and/or an early sign of pathology. Although limited, the normative data presented here is a step toward developing clinically useful microvascular parameters for ocular and/or systemic diseases., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Purpose: To investigate the association between the size and shape of the foveal avascular zone and retinal thickness in healthy subjects., Methods: In vivo imaging of the foveal microvasculature was performed on 32 subjects by using an adaptive optics scanning laser ophthalmoscope (AOSLO). Motion contrast maps of the AOSLO images were used to generate a montage revealing the foveal capillary network. Foveal avascular zone (FAZ) diameters along the horizontal (FAZH) and vertical (FAZV) meridians were measured on the montages. An asymmetry index (AI) of the FAZ was then computed as the ratio of the FAZH to FAZV. Retinal thickness was investigated by using spectral-domain optical coherence tomography (SDOCT). Inner retinal layer (INLFAZ) thickness and outer nuclear layer (ONLFAZ) thickness were measured at the edges of the FAZ on the horizontal and vertical SDOCT scans on the same eye., Results: The foveal capillary network was readily visualized in all subjects. As expected there was individual variation in the size and shape of the FAZ. Along the horizontal and vertical meridians, the mean±SD (μm) of the FAZ diameter was 607±217 and 574±155, respectively. The INLFAZ thickness was 68±9 and 66±9, and the ONLFAZ thickness was 103±13 and 105±11, respectively. The mean±SD of the AI was 1.03±0.27. The difference between FAZH and FAZV decreases with increasing FAZ area (P=0.004). Mean ONLFAZ was negatively correlated with FAZ effective diameter (P<0.0001). No significant correlation was found between mean INLFAZ and FAZ effective diameter (P=0.16)., Conclusions: Despite large individual variations in size and shape of the FAZ, the INLFAZ has a relatively constant thickness at the margins of the FAZ, suggesting the presence of retinal capillaries is needed to sustain an INLFAZ thickness greater than 60 μm. A smaller FAZ area is associated with a vertically elongated FAZ., (Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.)

Recent advances to the adaptive optics scanning light ophthalmoscope (AOSLO) have enabled finer in vivo assessment of the human retinal microvasculature. AOSLO confocal reflectance imaging has been coupled with oral fluorescein angiography (FA), enabling simultaneous acquisition of structural and perfusion images. AOSLO offset pinhole (OP) imaging combined with motion contrast post-processing techniques, are able to create a similar set of structural and perfusion images without the use of exogenous contrast agent. In this study, we evaluate the similarities and differences of the structural and perfusion images obtained by either method, in healthy control subjects and in patients with retinal vasculopathy including hypertensive retinopathy, diabetic retinopathy, and retinal vein occlusion. Our results show that AOSLO OP motion contrast provides perfusion maps comparable to those obtained with AOSLO FA, while AOSLO OP reflectance images provide additional information such as vessel wall fine structure not as readily visible in AOSLO confocal reflectance images. AOSLO OP offers a non-invasive alternative to AOSLO FA without the need for any exogenous contrast agent.

Purpose: Microaneurysms (MAs) are considered a hallmark of retinal vascular disease, yet what little is known about them is mostly based upon histology, not clinical observation. Here, we use the recently developed adaptive optics scanning light ophthalmoscope (AOSLO) fluorescein angiography (FA) to image human MAs in vivo and to expand on previously described MA morphologic classification schemes., Methods: Patients with vascular retinopathies (diabetic, hypertensive, and branch and central retinal vein occlusion) were imaged with reflectance AOSLO and AOSLO FA. Ninety-three MAs, from 14 eyes, were imaged and classified according to appearance into six morphologic groups: focal bulge, saccular, fusiform, mixed, pedunculated, and irregular. The MA perimeter, area, and feret maximum and minimum were correlated to morphology and retinal pathology. Select MAs were imaged longitudinally in two eyes., Results: Adaptive optics scanning light ophthalmoscope fluorescein angiography imaging revealed microscopic features of MAs not appreciated on conventional images. Saccular MAs were most prevalent (47%). No association was found between the type of retinal pathology and MA morphology (P = 0.44). Pedunculated and irregular MAs were among the largest MAs with average areas of 4188 and 4116 μm(2), respectively. Focal hypofluorescent regions were noted in 30% of MAs and were more likely to be associated with larger MAs (3086 vs. 1448 μm(2), P = 0.0001)., Conclusions: Retinal MAs can be classified in vivo into six different morphologic types, according to the geometry of their two-dimensional (2D) en face view. Adaptive optics scanning light ophthalmoscope fluorescein angiography imaging of MAs offers the possibility of studying microvascular change on a histologic scale, which may help our understanding of disease progression and treatment response.

We used a confocal adaptive optics scanning laser ophthalmoscope (AOSLO) to image the retina of subjects with non-proliferative diabetic retinopathy (NPDR). To improve visualization of different retinal features, the size and alignment of the confocal aperture were varied. The inner retinal layers contained clearly visualized retinal vessels. In diabetic subjects there was extensive capillary remodeling despite the subjects having only mild or moderate NPDR. Details of the retinal microvasculature were readily imaged with a larger confocal aperture. Hard exudates were observed with the AOSLO in all imaging modes. Photoreceptor layer images showed regions of bright cones and dark areas, corresponding in location to overlying vascular abnormalities and retinal edema. Clinically undetected intraretinal vessel remodeling and varying blood flow patterns were found. Perifoveal capillary diameters were larger in the diabetic subjects (p<0.01), and small arteriolar walls were thickened, based on wall to lumen measurements (p<.05). The results suggest that existing clinical classifications based on lower magnification clinical assessment may not adequately measure key vascular differences among individuals with NPDR.

Purpose: To improve the ability to image the vascular walls in the living human retina using multiply-scattered light imaging with an adaptive optics scanning laser ophthalmoscope (AOSLO)., Methods: In vivo arteriolar wall imaging was performed on eight healthy subjects using the Indiana AOSLO. Noninvasive imaging of vascular mural cells and wall structure were performed using systematic control of the position of a 10× Airy disk confocal aperture. Retinal arteries and arterioles were divided into four groups based on their lumen diameters (group 1: ≥100 μm; group 2: 50-99 μm; group 3: 10-49 μm; group 4: <10 μm)., Results: Fine structure of retinal vasculature and scattering behavior of erythrocytes were clearly visualized in all eight subjects. In group 1 vessels the mural cells were flatter and formed the outer layer of regularly spaced cells of a two (or more) layered vascular wall. In the vessels of groups 2 and 3, mural cells were visualized as distinct cells lying along the lumen of the blood vessel, resulting in a wall of irregular thickness. Vascular wall components were not readily identified in group 4 vessels., Conclusions: Our results show that retinal vascular mural cells and wall structure can be readily resolved in healthy subjects using AOSLO with multiply scattered light imaging for retinal vessels with a lumen diameter greater than or equal to 10 μm. Our noninvasive imaging approach allows direct assessment of the cellular structure of the vascular wall in vivo with potential applications in retinal vascular diseases such as diabetes and hypertension.

The adaptive optics scanning light ophthalmoscope (AOSLO) allows visualization of microscopic structures of the human retina in vivo. In this work, we demonstrate its application in combination with oral and intravenous (IV) fluorescein angiography (FA) to the in vivo visualization of the human retinal microvasculature. Ten healthy subjects ages 20 to 38 years were imaged using oral (7 and/or 20 mg/kg) and/or IV (500 mg) fluorescein. In agreement with current literature, there were no adverse effects among the patients receiving oral fluorescein while one patient receiving IV fluorescein experienced some nausea and heaving. We determined that all retinal capillary beds can be imaged using clinically accepted fluorescein dosages and safe light levels according to the ANSI Z136.1-2000 maximum permissible exposure. As expected, the 20 mg/kg oral dose showed higher image intensity for a longer period of time than did the 7 mg/kg oral and the 500 mg IV doses. The increased resolution of AOSLO FA, compared to conventional FA, offers great opportunity for studying physiological and pathological vascular processes.

Optical coherence tomography (OCT) and scanning laser ophthalmoscopy (SLO) are complementary imaging modalities, the combination of which can provide clinicians with a wealth of information to detect retinal diseases, monitor disease progression, or assess new therapies. Adaptive optics (AO) is a tool that enables correction of wavefront distortions from ocular aberrations. We have developed a multimodal adaptive optics system (MAOS) for high-resolution multifunctional use in a variety of research and clinical applications. The system integrates both OCT and SLO imaging channels into an AO beam path. The optics and hardware were designed with specific features for simultaneous SLO/OCT output, for high-fidelity AO correction, for use in humans, primates, and small animals, and for efficient location and orientation of retinal regions of interest. The MAOS system was tested on human subjects and rodents. The design, performance characterization, and initial representative results from the human and animal studies are presented and discussed.

Retinal vascular diseases are a leading cause of blindness and visual disability. The advent of adaptive optics retinal imaging has enabled us to image the retinal vascular at cellular resolutions, but imaging of the vasculature can be difficult due to the complex nature of the images, including features of many other retinal structures, such as the nerve fiber layer, glial and other cells. In this paper we show that varying the size and centration of the confocal aperture of an adaptive optics scanning laser ophthalmoscope (AOSLO) can increase sensitivity to multiply scattered light, especially light forward scattered from the vasculature and erythrocytes. The resulting technique was tested by imaging regions with different retinal tissue reflectivities as well as within the optic nerve head.

Purpose: We evaluated the relationship between cone photoreceptor packing density and outer nuclear layer (ONL) thickness within the central 15 degrees., Methods: Individual differences for healthy subjects in cone packing density and ONL thickness were examined in 8 younger and 8 older subjects, mean age 27.2 versus 56.2 years. Cone packing density was obtained using an adaptive optics scanning laser ophthalmoscope (AOSLO). The ONL thickness measurements included the ONL and the Henle fiber layer (ONL + HFL), and were obtained using spectral domain optical coherence tomography (SDOCT) and custom segmentation software., Results: There were sizeable individual differences in cone packing density and ONL + HFL thickness. Older subjects had on average lower cone packing densities, but thicker ONL + HFL measurements. Cone packing density and ONL + HFL thickness decreased with increasing retinal eccentricity. The ratio of the cone packing density-to-ONL2 was larger for the younger subjects group, and decreased with retinal eccentricity., Conclusions: The individual differences in cone packing density and ONL + HFL thickness are consistent with aging changes, indicating that normative aging data are necessary for fine comparisons in the early stages of disease or response to treatment. Our finding of ONL + HFL thickness increasing with aging is inconsistent with the hypothesis that ONL measurements with SDOCT depend only on the number of functioning cones, since in our older group cones were fewer, but thickness was greater.

We investigated the effect of localized visual stimulation on human retinal blood velocity using an adaptive optics scanning laser ophthalmoscope (AOSLO). To measure the blood velocity response, the AOSLO scanning raster was moved over the target arteries and red blood cell velocity was measured. Localized visual stimuli were delivered by projecting flicker patterns inside or outside the target artery's downstream region. The blood velocity increased in the presence of a flicker stimulus in the downstream region but not when outside the downstream region. The blood velocity increased more with larger area of stimulation. This increase was significant even when the stimulus was smaller than 600 μm × 600 μm. These findings suggest that when the retina regulates its blood flow to metabolic demands, it regulates blood velocity in the vascular system selectively, according to activity of neurons within its field of influence.

Although retinopathy of prematurity (ROP) is clinically characterized by abnormal retinal vessels at the posterior pole of the eye, it is also commonly characterized by vascular abnormalities in the anterior segment, visual dysfunction which is based in retinal dysfunction, and, most commonly of all, arrested eye growth and high refractive error, particularly (and paradoxically) myopia. The oxygen-induced retinopathy rat model of ROP presents neurovascular outcomes similar to the human disease, although it is not yet known if the "ROP rat" also models the small-eyed myopia characteristic of ROP. In this study, magnetic resonance images (MRIs) of albino (Sprague-Dawley) and pigmented (Long-Evans) ROP rat eyes, and age- and strain-matched room-air-reared (RAR) controls, were examined. The positions and curvatures of the various optical media were measured and the refractive state (℞) of each eye estimated based on a previously published model. Even in adulthood (postnatal day 50), Sprague-Dawley and Long-Evans ROP rats were significantly myopic compared to strain-matched controls. The myopia in the Long-Evans ROP rats was more severe than in the Sprague-Dawley ROP rats, which also had significantly shorter axial lengths. These data reveal the ROP rat to be a novel and potentially informative approach to investigating physiological mechanisms in myopia in general and the myopia peculiar to ROP in particular.

Introduction: Research has shown that people with chronic pain have difficulty directing their attention away from pain. A mental strategy that incorporates focused attention and distraction has been found to modulate the perception of pain intensity. That strategy involves placing attention on the nociceptive stimulus felt and shifting attention to a self-generated sub-nociceptive image and rehearsing it. Event-related potential was used to study the possible processes associated with the focus-then-orient strategy., Methods: Eighteen pain-free participants received different levels of 50-ms nociceptive stimulations elicited by electric shocks at the right lateral malleolus (ankle). In perception trials, participants maintained the perceived nociceptive stimulus in working memory for 3,000 ms. In imagery trials, participants mentally generated and maintained the corresponding sub-nociceptive image they had learned previously. After both types of trials, participants evaluated the pain intensity of the incoming stimulus by recalling the feeling of the nociceptive stimulation at the beginning of the trial., Results: Shifting attention from the incoming nociceptive to a self-generated sub-nociceptive image elicited central P2 and centro-parietal P3 waves, which were found to correlate with proportional scores on the Stroop Test. They were followed by a frontal N400 and a parietal P600, denoting generation of sub-nociceptive images in working memory. The voltages elicited in these potentials correlated moderately with attenuation of the pain ratings of the recalled nociceptive stimulations., Conclusions: Focus-and-orient attention across nociceptive and sub-nociceptive images appears to be related to response inhibition. Mental rehearsal of the sub-nociceptive images was found to modulate the perception of the nociceptive sensation felt prior to the imagery. Such modulation seems to be mediated by generating and maintaining sub-nociceptive images in working memory. Future studies should explore the mental processes associated with orienting attention for pain modulation among people with pathological pain and frontal lobe dysfunction.

We evaluated the relationship between the size of the peripapillary crescent and the axial length (AL) of the eye as well as the fine structure of the peripapillary crescent in selected eyes. Infrared fundus imaging and spectral domain optical coherence tomography (SDOCT) (Spectralis HRA+OCT, Heidelberg Engineering, Germany) centered at the fovea were performed on 72 healthy adults. On the infrared fundus images, we measured (a) the distance between the foveola and the temporal edge of the optic disc (FOD) and (b) the distance between the foveola and the temporal edge of the peripapillary crescent (FOC) (if present). A peripapillary crescent presented at the nasal margin of the disc in 64% of the subjects. The FOD and FOC were 4.22mm±0.46 and 3.97mm±0.25, respectively. Only the FOD was significantly correlated with axial length. As AL increased by 10%, the FOD increased by 13%, the outer neural retina only expanded by 4% (as indicated by the FOC). This result emphasizes that retinal stretching may not mirror scleral growth, and the existence in some eyes of a difference between the photoreceptor margin and retinal pigment epithelium (RPE) margin suggests that within the retina there could be slippage during eye growth., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Purpose: To study the variation of cone photoreceptor packing density across the retina in healthy subjects of different ages., Methods: High-resolution adaptive optics scanning laser ophthalmoscope (AOSLO) systems were used to systematically image the retinas of two groups of subjects of different ages. Ten younger subjects (age range, 22-35 years) and 10 older subjects (age range, 50-65 years) were tested. Strips of cone photoreceptors, approximately 12° × 1.8° long were imaged for each of the four primary retinal meridians: superior, inferior, nasal, and temporal. Cone photoreceptors within the strips were counted, and cone photoreceptor packing density was calculated. Statistical analysis (three-way ANOVA) was used to calculate the interaction for cone photoreceptor packing density between age, meridian, and eccentricity., Results: As expected, cone photoreceptor packing density was higher close to the fovea and decreased with increasing retinal eccentricity from 0.18 to 3.5 mm (∼0.6-12°). Older subjects had approximately 75% of the cone density at 0.18 mm (∼0.6°), and this difference decreased rapidly with eccentricity, with the two groups having similar cone photoreceptor packing densities beyond 0.5 mm retinal eccentricity on average., Conclusions: Cone packing density in the living human retina decreases as a function of age within the foveal center with the largest difference being found at our most central measurement site. At all ages, the retina showed meridional difference in cone densities, with cone photoreceptor packing density decreasing faster with increasing eccentricity in the vertical dimensions than in the horizontal dimensions.

Purpose: To quantitatively model the changes in blood velocity profiles for different cardiac phases in human retinal vessels., Methods: An adaptive optics scanning laser ophthalmoscope (AOSLO) was used to measure blood velocity profiles in three healthy subjects. Blood velocity was measured by tracking erythrocytes moving across a scanning line. From the radial position of the cells within the lumen, the blood velocity profile was computed. The cardiac pulsatility was recorded with a cardiac signal monitor., Results: The shape of the blood velocity profile in retinal arteries changed systematically during the cardiac cycle, with the flattest profile occurring during the diastolic phase. The measured blood velocity profiles were typically flatter than the commonly assumed parabolic shape. The flatness increased with decreasing vessel size. For the large veins (>80 μm), the ratio of the centerline velocity to the cross-sectional average velocity was between 1.50 and 1.65. This ratio decreased to 1.36 in the smallest vein studied (32 μm). Velocity profiles downstream from a venous confluence showed two peaks at 120 μm from the confluence, but a single velocity peak 500 μm downstream from the confluence., Conclusions: The cardiac cycle influences the blood flow velocity profiles systematically in retinal arteries but not in veins. Parabolic flow was not found in even the largest vessels studied, and deviations from parabolic flow increased in smaller vessels. The measurements are sensitive enough to measure the dual-humped blood velocity profile at a vein confluence.

We have used an adaptive-optics scanning laser ophthalmoscope to image the cone photoreceptor mosaic throughout the central 10 degrees -12 degrees of the retina for four normal subjects. We then constructed montages of the images and processed the montages to determine cone locations. Cone densities range from approximately 10,000 cones/mm2 at 7 degrees to 40,000 cones/mm2 at 1 degrees . The smallest cones were not resolved in the center of the fovea. From the locations of the cones we also analyzed the packing properties of the cone mosaic, finding that all four subjects had a slight cone streak of increased cone density and that, in agreement with previous studies using different approaches, the packing geometry decreased in regularity from the fovea toward the periphery. We also found variations in packing density between subjects and in local anisotropy across retinal locations. The complete montages are presented for download, as well as the estimated cone locations.

Purpose: To describe the prevalence, severity, and associated risk factors of diabetic retinopathy among different racial groups (whites, blacks, Hispanics, and Asians) within an urban, underserved population., Methods: 2-field non-mydriatic retinal photographs of each eye were reviewed for 1073 patients referred to the San Francisco General Hospital mobile eye service, the Eye Van, for diabetic retinopathy screening. Presence and severity of diabetic retinopathy was determined based on a modification of the Airlie House classification system., Results: The prevalence of any retinopathy among all diabetics was 15.7%. There was no statistical difference in the prevalence of retinopathy among the racial groups. Significant independent predictors of presence and severity of retinopathy were longer duration of diabetes, and use of oral hypoglycemic medication or insulin (P < 0.05). Gender, age, primary language, income, and co-diagnosis of hypertension were not correlated., Conclusions: In this population of similar socioeconomic status and access to healthcare, race was not an independent predictor of diabetic retinopathy. This suggests that racial differences described in previous studies may be eliminated when social factors are equalized.