Repeatability and reproducibility of optic nerve head perfusion measurements using optical coherence tomography angiography

Short-Wavelength Light-Blocking Filters and Oral Melatonin Administration in Patients With Retinitis Pigmentosa: Protocol for a Randomized Controlled Trial

BACKGROUND

The medical community is beginning to recognize that retinitis pigmentosa (RP), due to its disabling progression, eventually leads to a reduction in the patient´s quality of life, a direct economic impact, and an increase in the burden on the health care system. There is no curative treatment for the origin of the disease, and most of the current interventions fail in reducing the associated negative psychological states, such as anxiety and depression, which lead to increased variability of vision and pose a continuous threat to the patient's independence.

OBJECTIVE

The aim of this study is to assess the effect of oral melatonin (OM) administration alone and combined with short-wavelength light (SWL)-blocking filters on patients with RP and test their effectiveness in improving the level of stress and sleep problems in many of these patients.

METHODS

We have developed a low-cost therapy protocol for patients with RP with sleep disorders and negative psychological stress. Patients will be randomized to receive a combined intervention with SWL-blocking filters and OM, SWL-blocking filters alone, or OM alone. There will also be a nonintervention arm as a control group. This study will be conducted across 2 retinal units in patients with RP with sleep disorders and high perceived stress and anxiety score reports. Patients will be assessed in the preintervention period, weekly during the 4 weeks of intervention, and then at 6 months postintervention. The primary outcomes are the differences in changes from baseline to postintervention in hormone release (α-amylase, cortisol, and melatonin) and sleep quality, as measured with the visual analog scale. Secondary outcome measures include clinical macular changes, as measured with optical coherence tomography and optical coherence tomography angiography; retinal function, as measured using the visual field and best-corrected visual acuity; sleep data collected from personal wearables; and several patient-reported variables, such as self-recorded sleep diaries, quality of life, perceived stress, and functional status.

RESULTS

This project is still a study protocol and has not yet started. Bibliographic research for information for its justification began in 2020, and this working group is currently seeking start-up funding. As soon as we have the necessary means, we will proceed with the registration and organization prior to the preliminary phase.

CONCLUSIONS

In this feasibility randomized clinical controlled trial, we will compare the effects of SWL blocking alone, administration of OM alone, and a combined intervention with both in patients with RP. We present this study so that it may be replicated and incorporated into future studies at other institutions, as well as applied to additional inherited retinal dystrophies. The goal of presenting this protocol is to aid recent efforts in reducing the impact of sleeping disorders and other psychological disorders on the quality of life in patients with RP and recovering their self-autonomy. In addition, the results of this study will represent a significant step toward developing a novel low-cost therapy for patients with RP and validating a novel therapeutic target.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/49196.

Diurnal change of retinal vessel density related to hemodynamic variation in treatment-naïve low-teens normal-tension glaucoma

This study undertook to investigate the diurnal variation of optical coherence tomography angiography (OCTA) -derived retinal vessel density (RVD) in glaucoma patients with low baseline intraocular pressure (IOP). A prospective evaluation was performed on low-teens normal-tension glaucoma (low-teens NTG) patients with pre-treatment IOP < 15 mmHg and 32 healthy subjects. Superficial peripapillary and macular RVD by OCTA, IOP, and systemic blood pressure (BP) were all measured four times per day (from 9:00 a.m. to 6:00 p.m.). In the low-teens NTG group, the magnitude of diurnal changes in peripapillary RVD and macular RVD were greater than those in the healthy group. Diurnal variations of diastolic BP (DBP) and mean ocular perfusion pressure (MOPP) also were greater in the low-teens NTG group. As for the patterns of diurnal RVD change, the inferior and temporal sections of macular RVD showed significant differences between the two groups. Diurnal changes of RVD and MOPP and were greater than those in healthy eyes. The macular RVD and MOPP showed different diurnal patterns between the two groups. From these findings, OCTA-derived RVD variation could be related to hemodynamic variability in low-teens NTG.

Reproducibility of peripapillary, optic nerve head and macular vessel density by OCT-A according to glaucoma severity staging

OBJECTIVE

To assess the reproducibility of peripapillary, optic nerve head (ONH-PP) and macular vessel density (VD) by Spectral Domain optical coherence tomography angiography (SD OCT-A) in glaucoma patients and healthy subjects.

METHODS

Cross-sectional study assessing 63 eyes of 63 subjects, including 33 glaucoma patients and 30 healthy subjects. Glaucoma was classified in mild, moderate, or advanced. Two consecutive scans were acquired by Spectralis Module OCT-A (Heidelberg, Germany), and provided images of the superficial vascular complex (SVC), nerve fiber layer vascular plexus (NFLVP), superficial vascular plexus (SVP); deep vascular complex (DVC), intermediate capillary plexus (ICP) and deep capillary plexus (DCP). VD (%) was calculated by AngioTool. Intraclass correlation coefficients (ICCs) and coefficients of variation (CV) were calculated.

RESULTS

Among ONH-PP VD, better ICC presented advanced (0.83-0.97) and moderate glaucoma (0.86-0.96) compared with mild glaucoma (0.64-0.86). For the macular VD reproducibility, ICC results for superficial retinal layers were better for mild glaucoma (0.94-0.96) followed by moderated (0.88-0.93) and advanced glaucoma (0.85-0.91), and for deeper retinal layers ICC was better for moderate glaucoma (0.96-0.95) followed by advanced (0.80-0.86) and mild glaucoma (0.74-0.91). CVs ranged from 2.2%% to 10.94%. Among healthy subjects, ICCs for the ONH-PP VD measurements (0.91-0.99) and for the macular VD measurements (0.93-0.97) were excellent in all layers, with CVs from 1.65% to 10.33%.

CONCLUSIONS

SD OCT-A used to quantify macular and ONH-PP VD showed excellent and good reproducibility in most layers of the retina, both in healthy subjects and in glaucoma patients regardless of the severity of the disease.

Thinner Central Corneal Thickness is Associated with a Decreased Parapapillary Vessel Density in Normal Tension Glaucoma

This retrospective cross-sectional study, which enrolled 124 normal tension glaucoma (NTG) eyes and 68 healthy eyes as the control, determined the association between central corneal thickness (CCT) and ocular parameters in NTG. CCT was measured using the Pentacam® system, optical coherence tomography angiography (OCT-A) was adopted to measure the peripapillary and macular area VDs, and spatial data were based on the Garway–Heath map as illustrated in OCT-A. Univariate and multivariate linear regressions were used to statistically analyze for associations between CCT and other factors. In this study, the mean age was similar for both the NTG and control groups. The mean CCT of the NTG group was significantly thinner than that of the control group (533.97 ± 33.11 µm vs. 546.78 ± 38.21 µm; $p$  = .022). Considering all the factors, CCT negatively correlated with visual field (VF) pattern standard deviation (univariate, $p$  = .045). To analyze structural and functional factors separately, we found a significant positive correlation between CCT and whole disc radial peripapillary capillary VD (VDRPC; multivariate, $p$  = .019). To analyze the relationship between all factors and sectoral changes in VDRPC, a significant positive correlation was observed between CCT and inferior temporal VDRPC (univariate, $p$  = .039) and inferior nasal VDRPC (VDRPC IN; univariate, $p$  = .048). In conclusion, this novel study shows that among NTG participants, a thinner cornea correlated with weaker biomechanical properties susceptible to optic nerve tissue displacement, especially in response to mild transient elevation of IOP, leads to compromised ocular microcirculation.

Recognition of intracranial hypertension using handheld optical coherence tomography in children (RIO Study): a diagnostic accuracy study protocol

INTRODUCTION

Paediatric intracranial hypertension (IH) is a rare but serious condition that can pose deleterious effects on the brain and vision. Estimating intracranial pressure (ICP) in children is difficult. Gold standard direct ICP measurement is invasive and carries risk. It is impractical to routinely perform direct ICP measurements over time for all children at risk of IH. This study proposes to assess the diagnostic accuracy of handheld optical coherence tomography (OCT), a non-invasive ocular imaging method, to detect IH in children.

METHODS AND ANALYSIS

This is a prospective study evaluating the diagnostic accuracy of handheld OCT for IH in at risk children. Inclusion criteria include clinical and/or genetic diagnosis of craniosynostosis, idiopathic intracranial hypertension, space occupying lesion or other conditions association with IH and age 0-18 years old. Exclusion criteria include patients older than 18 years of age and/or absence of condition placing the child at risk of IH. The primary outcome measures are handheld OCT and 48-hour ICP assessments, which will be used for diagnostic accuracy testing (sensitivity, specificity, positive predictive value, negative predictive value and accuracy). Main secondary outcome measures include visual acuity, fundoscopic examination, contrast sensitivity, visual field testing and visual evoked potentials, wherever possible.

ETHICS AND DISSEMINATION

Ethical approval was granted for this study by the East Midlands Nottingham 2 Research Ethics committee (UOL0348/IRAS 105137). Our findings will be disseminated through presentation at relevant meetings, peer-reviewed publication and via the popular media.

TRIAL REGISTRATION NUMBER

ISRCTN52858719.

Repeatability of Peripapillary OCT Angiography in Neurodegenerative Disease

Purpose

To assess the repeatability of peripapillary OCT angiography (OCTA) in those with Alzheimer disease (AD), mild cognitive impairment (MCI), Parkinson disease (PD), or normal cognition.

Design

Cross-sectional.

Participants

Patients with a clinical diagnosis of AD, MCI, PD, or normal cognition were imaged. Those with glaucoma, diabetes mellitus, vitreoretinal pathology, and poor-quality images were excluded.

Methods

Each eligible eye of each participant underwent 2 OCTA 4.5 × 4.5-mm peripapillary scans in a single session using a Zeiss Cirrus HD-OCT 5000 with AngioPlex (Carl Zeiss Meditec). The Zeiss software (v11.0.0.29946) quantified measures of perfusion in the radial peripapillary capillary (RPC) plexus in 4 sectors (superior, nasal, inferior, temporal). The average of these sectors was calculated and reported.

Main Outcome Measures

Radial peripapillary capillary plexus perfusion was quantified using 2 parameters: capillary perfusion density (CPD) and capillary flux index (CFI). Intraclass correlation coefficients (ICCs) were used to quantify repeatability. For subjects who had both eyes included, the average values of each scan pair were used to assess interocular symmetry of CPD and CFI.

Results

Of 374 eyes, 46 were from participants who had AD, 85 were from participants who had MCI, 87 were from participants who had PD, and 156 were from participants who had normal cognition. Capillary perfusion density ICC in AD = 0.88 (95% confidence interval [CI], 0.79–0.93), MCI = 0.95 (0.92–0.96), PD = 0.91 (0.87–0.94), and controls = 0.90 (0.87–0.93). Capillary flux index ICC in AD = 0.82 (0.70–0.90), MCI = 0.87 (0.80–0.91), PD = 0.91 (0.87–0.94) and controls = 0.85 (0.79–0.89). There were no significant differences in interocular variation in average CPD and CFI in AD, MCI, or PD (all P > 0.05). Isolated interocular sectoral CPD differences were noted in AD (nasal, P = 0.049; temporal, P = 0.024), PD (nasal, P = 0.036), and controls (nasal, P = 0.016). Interocular differences in CFI in the superior sector in MCI (P = 0.028) and in average CFI for controls (P = 0.035) were observed.

Conclusions

Peripapillary OCTA repeatability in AD, MCI, and PD is good-excellent and similar to those with normal cognition. Insignificant interocular asymmetry in peripapillary OCTA suggests neurodegeneration may proceed uniformly; future studies may reveal the appropriateness of single-eye imaging.

Analysis of Foveal Microvascular Abnormalities in Patients with Systemic Lupus Erythematosus Using Optical Coherence Tomography Angiography

Purpose: To analyze the abnormalities of foveal microvasculature in patients with systemic lupus erythematosus (SLE).Methods: A cross-sectional study of 41 eyes of patients diagnosed with SLE and 40 eyes of healthy controls. Sections measuring 6 mm×6 mm centered on the fovea were obtained using optical coherence tomography angiography (OCTA).Results: The area and perimeter of foveal avascular zone (FAZ) in SLE patients were greater than those in controls (both p < .05). The parafoveal vessel densities in the deep capillary plexus (DCP) of SLE patients were significantly decreased than those in controls (p < .001). There was a negative correlation between SLE disease activity index and parafoveal vessel density in DCP (p < .05).Conclusion: Enlargement of the FAZ and decline of the parafoveal vessel density of DCP were revealed by OCTA in patients with SLE. Moreover, a negative correlation between parafoveal vessel density in DCP and disease activity index was detected in SLE patients.

Current and novel multi-imaging modalities to assess retinal oxygenation and blood flow

Retinal ischemia characterizes the underlying pathology in a multitude of retinal diseases that can ultimately lead to vision loss. A variety of novel imaging modalities have been developed to characterize retinal ischemia by measuring retinal oxygenation and blood flow in-vivo. These technologies offer valuable insight into the earliest pathophysiologic changes within the retina and provide physicians and researchers with new diagnostic and monitoring capabilities. Future retinal imaging technologies with the capability to provide affordable, noninvasive, and comprehensive data on oxygen saturation, vasculature, and blood flow mechanics are needed. This review will highlight current and future trends in multimodal imaging to assess retinal blood flow and oxygenation.

Impact of image averaging on vessel detection using optical coherence tomography angiography in eyes with macular oedema and in healthy eyes

Purpose

To assess the repeatability of multiple automatic vessel density (VD) measurements and the effect of image averaging on vessel detection by optical coherence tomography angiography (OCTA).

Methods

An observational study was conducted in a series of healthy volunteers and patients with macular oedema. Five sequential OCTA images were acquired for each eye using the OptoVue HD device. The effect of the averaging of the 5 acquisitions on vessel detection was analysed quantitatively using a pixel-by-pixel automated analysis. In addition, two independent retina experts qualitatively assessed the change in vessel detection in averaged images segmented in 9 boxes and compared to the first non-averaged image.

Results

The automatic VD measurement in OCTA images showed a good repeatability with an overall mean intra-class correlation coefficient (ICC) of 0.924. The mean ICC was higher in healthy eyes compared to eyes with macular oedema (0.877 versus 0.960; p < 0.001) and in the superficial vascular plexus versus the deep vascular complex (0.967 versus 0.888; p = 0.001). The quantitative analysis of the effect of the averaging showed that averaged images had a mean gain of 790.4 pixels/box, located around or completing interruptions in the vessel walls, and a mean loss of 727.2 pixels/box. The qualitative analysis of the averaged images showed that 99.6% of boxes in the averaged images had a gain in vessel detection (i.e., vessels detected in the averaged image but not in the non-averaged image). The loss of pixels was due to a reduction in background noise and motion artifacts in all cases and no case of loss of vessel detection was observed.

Conclusion

The automatic VD measurement using the OptoVue HD device showed a good repeatability in 5 acquisitions in a row setting. Averaging images increased vessel detection, and in about a third of boxes, decreased the background noise, both in healthy eyes and, in a greater proportion, in eyes with macular oedema.

OCT-A evaluation of radiation vasculopathy following slotted plaque brachytherapy

PURPOSE

To determine a reliable diagnostic method to reveal and monitor subclinical progression of neural and perineural radiation vasculopathy.

METHODS

A retrospective cross-sectional study, where optical coherence tomography angiography (OCT-A) imaging data was collected and analyzed from 22 consecutive patients that had been treated with circumneural slotted plaque brachytherapy for peripapillary, juxtapapillary, or circumpapillary choroidal melanomas. Pre-operative dosimetry of palladium-103 radiation dose to the optic nerve and fovea were collected. Quantified differences in OCT-A-measured vessel density and length in treated verses untreated contralateral control eyes were collected. Vessel density and length were correlated to radiation dose, plaque slot depth, visual acuity outcomes, and circumpapillary retinal nerve fiber layer thickness.

RESULTS

Patients had post-irradiation follow-up of median 39 months, interquartile range 62 months). The mean optic disc radiation dose was 89.9 Gy ± 39.2 (86.5, 30.8-189.0). In comparison to controls, OCT-A imaging revealed significant differences in radial peripapillary capillary vessel density (18 μm² in case eyes, 34 μm² in control eyes; p < 0.001) and length (10 μm in case eyes, 14 μm in control eyes; p < 0.001). Change in vessel density did not show a significant correlation to radiation dose, slot depth, or visual acuity. However, change in vessel length was significantly correlated to radiation dose (p = 0.049) and change in visual acuity (p < 0.001).

CONCLUSIONS

OCT-A imaging revealed that radial peripapillary capillary vessel density and length were significantly reduced after circumneural irradiation for choroidal melanoma. Therefore, OCT-A imaging can be used to monitor progression of papillary vasculopathy associated with radiation optic neuropathy.

Past, present and future role of retinal imaging in neurodegenerative disease

Retinal imaging technology is rapidly advancing and can provide ever-increasing amounts of information about the structure, function and molecular composition of retinal tissue in humans in vivo. Most importantly, this information can be obtained rapidly, non-invasively and in many cases using Food and Drug Administration-approved devices that are commercially available. Technologies such as optical coherence tomography have dramatically changed our understanding of retinal disease and in many cases have significantly improved their clinical management. Since the retina is an extension of the brain and shares a common embryological origin with the central nervous system, there has also been intense interest in leveraging the expanding armamentarium of retinal imaging technology to understand, diagnose and monitor neurological diseases. This is particularly appealing because of the high spatial resolution, relatively low-cost and wide availability of retinal imaging modalities such as fundus photography or OCT compared to brain imaging modalities such as magnetic resonance imaging or positron emission tomography. The purpose of this article is to review and synthesize current research about retinal imaging in neurodegenerative disease by providing examples from the literature and elaborating on limitations, challenges and future directions. We begin by providing a general background of the most relevant retinal imaging modalities to ensure that the reader has a foundation on which to understand the clinical studies that are subsequently discussed. We then review the application and results of retinal imaging methodologies to several prevalent neurodegenerative diseases where extensive work has been done including sporadic late onset Alzheimer's Disease, Parkinson's Disease and Huntington's Disease. We also discuss Autosomal Dominant Alzheimer's Disease and cerebrovascular small vessel disease, where the application of retinal imaging holds promise but data is currently scarce. Although cerebrovascular disease is not generally considered a neurodegenerative process, it is both a confounder and contributor to neurodegenerative disease processes that requires more attention. Finally, we discuss ongoing efforts to overcome the limitations in the field and unmet clinical and scientific needs.

Repeatability of Peripapillary Optical Coherence Tomography Angiography Parameters in Older Adults

Purpose:

This work assesses the intrasession repeatability of capillary perfusion density (CPD) and capillary flux index (CFI) measurements on peripapillary optical coherence tomography angiography (OCTA) in healthy eyes of older adults.

Methods:

In this cross-sectional study, healthy volunteers aged 50 years or older underwent 4.5 × 4.5 mm OCTA imaging centered on the optic nerve head using Zeiss Cirrus HD-5000 AngioPlex (Carl Zeiss Meditec). Two consecutive images were acquired in the same eye during a single study session. CPD and CFI were assessed using AngioPlex Software (version 11.0.0.29946) for the radial peripapillary capillary plexus (average over whole scan area) and 4 quadrants (superior, inferior, temporal, and nasal). CPD and CFI repeatability was assessed by intraclass correlation (ICC), mean interocular differences using 2-tailed t test, and association with age using generalized estimating equations.

Results:

A total of 150 images were acquired from 75 eyes of 47 patients. For CPD, ICC results ranged from 0.7160 (nasal CPD) to 0.9218 (average CPD). For CFI, ICC results ranged from 0.6167 (temporal CFI) to 0.8976 (inferior CFI). Temporal CFI was significantly different between right and left eyes of the same patient ( P = .03). CPD and CFI decreased with age in all analyses (average CPD β coefficient –0.00172, P < .001; average CFI β coefficient −0.00278, P < .001).

Conclusions:

Moderate to good repeatability was observed for most peripapillary OCTA metrics; temporal measurements were least repeatable for CPD and CFI. Peripapillary CPD and CFI decrease with age even beyond the fifth decade in healthy older adults.

Repeatability of Macular and Optic Nerve Head Measurements by Optical Coherence Tomography Angiography in Healthy Children

Aims: To evaluate the repeatability of the peripapillary and macular vascular parameters using optical coherence tomography angiography (OCT-A) in healthy children.Materials and methods: Cross-sectional study including 34 eyes of 34 healthy children. After a complete medical examination, two consecutive OCT-A exams were done using AngioPlex Cirrus 5000 (Carl Zeiss Meditec, Dublin, CA, USA) in the same session. The scan area used was 6 × 6 mm for the analysis of the superficial vascular plexus (SVP) in the macula, and 4.5 × 4.5 mm for the peripapillary plexus. To study the repeatability of the measurements, the intraclass correlation coefficient (ICC) and the coefficient of variation (CV) of each pair of exams were calculated.Results: The mean age of the children included was 10.77 ± 2.49 years (range 6 to 15 years). Good and excellent ICCs were obtained for all the parameters considered. Peripapillary vascular parameters showed greater reproducibility than macular ones (global peripapillary perfusion density (pPD): ICC = 0.834 CV = 0.89% vs. whole macular area PD (w-mPD): ICC = 0.697 CV = 3.49%; global peripapillary flux index (FI): ICC = 0.858 CV = 1.28%; whole macular area vascular density (VD): ICC = 0.699 CV = 3.30%). Amongst the macular parameters, the characteristics of the foveal avascular zone (FAZ) were the ones showing higher rates of repeatability (FAZ circularity: ICC = 0.858 CV = 8.83%).Conclusion: OCT-A is a non-invasive, time-efficient technology that may be useful in the evaluation of the retinal and peripapillary vascular network in healthy children. The repeatability of the measures will allow the follow-up and evaluation of any change occurring in the macular or optic nerve perfusion.

Association between risk factors and retinal nerve fiber layer loss in early stages of diabetic retinopathy

AIM

To investigate the changes of retinal nerve fiber layer (RNFL) among normal individuals, diabetic patients without diabetic retinopathy (NDR) and non-proliferative diabetic retinopathy (NPDR), and explore the possible risk factors of early diabetic retinopathy (DR).

METHODS

In this cross-sectional study, 107 participants were divided in three groups. Totally 31 normal individuals (control group), 40 diabetic patients without DR (NDR group) and 36 patients with NPDR (NPDR group) were included. Optical coherence tomography (OCT) was used to detect RNFL thickness and other optic disc parameters among different groups. The potential association between RNFL loss and systemic risk factors were assessed for DR, including diabetes duration, body mass index (BMI), hemoglobin A1c (HbA1c), serum lipids, and blood pressure.

RESULTS

The average and each quadrant RNFL thickness were thinner in NPDR group compared to control group of the right (P=0.00, P=0.01, P=0.01, P=0.02, P=0.04) and left eyes (P=0.00, P=0.00, P=0.00, P=0.03, P=0.04). The average, superior and inferior RNFL thickness were thinner in NDR group compared to the NPDR group of the right (P=0.00, P=0.02, P=0.03) and left eyes (P=0.00, P=0.00, P=0.01). Diabetic duration was negatively correlated with the superior, inferior, and average RNFL thickness of the right (r=-0.385, P=0.001; r=-0.366, P=0.001; r=-0.503, P=0.000) and left eyes (r=-0.271, P=0.018; r=0.278, P=0.015; r=-0.260, P=0.023). HbA1c was negatively correlated with the superior, inferior, and average RNFL thickness of the right (r=-0.316 P=0.005; r=-0.414, P=0.000; r=-0.418, P=0.000) and left eyes (r=-0.367, P=0.001; r=-0.250, P=0.030; r=-0.393, P=0.000). Systolic pressure was negatively correlated with the inferior and average RNFL thickness of the right eye (r=-0.402, P=0.000; r=-0.371, P=0.001) and was negatively correlated with the superior and average RNFL thickness of the left eye (r=-0.264, P=0.021; r=-0.233, P=0.043).

CONCLUSION

RNFL loss, especially in the superior and inferior quadrants, may be the earliest structural change of the retina in diabetic patients, and is also associated with diabetic duration, HbA1c, and systolic pressure.

Effect of systemic blood pressure on optical coherence tomography angiography in glaucoma patients

BACKGROUND

The association between retinal microvascular structure and glaucoma has been revealed in multiple studies using optical tomography angiography (OCTA), but limited information on the macular vessel density (mVD) in patients with glaucoma is available. In this study, we tried to identity the factors that affected macular VD (mVD) in glaucomatous eyes.

METHODS

This retrospective cross-sectional study evaluated OCT and OCTA images from 92 eyes from 58 healthy subjects and 179 eyes from 103 glaucoma patients using the SD-OCT database from July 2017 to July 2018. Glaucomatous eyes were further divided into two groups according to history of disc haemorrhage (DH). Association between mVD and demographic characteristics, ganglion cell-inner plexiform layer (GCIPL) thickness, visual field mean deviation (MD) and systemic blood pressure was analysed in each group.

RESULTS

In both healthy and glaucomatous eyes, mVD was inversely associated with age (β = -0.035, P = 0.025; β = -0.039, P = 0.018). In the glaucomatous eyes, mVD was significantly decreased, as the MD value was worse (β = 0.109, P = 0.002). In glaucomatous eyes with DH, mVD decreased as blood pressure increased (β = -0.111, P = 0.003) CONCLUSIONS: Reduced mVD is more common in older individuals in both healthy and glaucomatous eyes, and correlates with functional deterioration than structural damage in glaucomatous eyes. In glaucomatous eyes with DH, high systemic BP is associated with a reduction in mVD. This may indicate that glaucoma patients with DH are more susceptible to vascular damage secondary to hypertension.

Altered visual functions, macular ganglion cell and papillary retinal nerve fiber layer thickness in early-treated adult PKU patients

Purpose

Retinal changes are poorly described in early treated phenylketonuria (ETPKU). We aimed to investigate possible visual functional and ocular microstructural changes in adult patients with ETPKU. Optical coherence tomography (OCT) and its angiography (OCTA) data from patients with PKU were compared to healthy controls.

Methods

In this prospective, monocentric, cross-sectional, case-control study 50 patients with ETPKU and 50 healthy subjects were evaluated with OCT and OCTA. Measurements were performed on right eyes. The following visual function parameters were studied: best corrected visual acuity (BCVA), spherical equivalent (SE), contrast sensitivity and near stereoacuity; microstructural parameters: retinal nerve fiber layer thickness (RNFLT), ganglion cell layer (GCC) thickness, focal loss of volume (FLV), global loss of volume (GLV), peripapillary, papillary vessel density (VD), ocular axial length (AL) and intraocular pressure (IOP).

Results

Among functional tests there were significant differences in contrast sensitivity at 1.5 (p < 0.001), 6 (p < 0.013), 12 (p < 0.001), 18 (p < 0.003) cycles per degree, in near stereoacuity (Titmus Wirt circles, p < 0.001) and in best corrected visual acuity (BCVA, p < 0.001). A statistically significant, moderate positive linear correlation was observed between BCVA and average Phe levels over the last ten years (β = 0.49, p < 0.001). The average (p < 0.001), superior (p < 0.001) inferior GCC (p < 0.001), the FLV (p < 0.003), GLV (p < 0.001) and the average RNFLT (p < 0.004) values of the PKU group were significantly lower than the controls. The serum phenylalanine level (Phe) in the PKU group negatively correlated with inferior (−0.32, p < 0.007), superior (r = −0.26, p < 0.028) and average (−0.29 p < 0.014) RNFL and with AL (−0.32, p < 0.026). In AL we detected a significant difference (p < 0.04) between the good and suboptimal dietary controlled group. There was no significant difference between the ETPKU and control group in the measured vessel density parameters and in IOP.

Conclusions

Our results suggest that functional and ocular microstructural defects are present in patients with PKU, and some of them may depend on dietary control. The mechanism is unclear, but the correlation indicates the importance of strict dietary control in terms of preservation of retinal functions.

Effect of Scan Size on Glaucoma Diagnostic Performance Using OCT Angiography En Face Images of the Radial Peripapillary Capillaries

PRECIS

When comparing 4.5×4.5 mm to 6.0×6.0 mm optical coherence tomography angiography scans of the radial peripapillary capillaries (RPCs) for glaucoma diagnostic capability, there was a trend of 4.5 scans outperforming 6.0 scans, especially for inferior, nasal, and superior quadrants.

OBJECTIVES

The main purpose of this study was to compare diagnostic ability of peripapillary vessel parameters from 4.5×4.5 mm (4.5) and 6.0×6.0 mm (6.0) spectral-domain optical coherence tomography angiography scans of the RPC in detecting primary open-angle glaucoma from nonglaucoma eyes.

METHODS

Consecutive patients from an academic glaucoma clinic underwent 4.5 and 6.0 scans (CIRRUS HD-OCT 5000 with AngioPlex OCT Angiography; ZEISS, Dublin, CA). Automatic segmentation created en face RPC images. Vessel area density, vessel skeleton density, and flux were calculated using custom quantification software, and perfusion density and flux index (FI) using automated quantification software. Area under the curve statistics included age and hypertension in the analysis.

RESULTS

Of 173 eyes from 123 patients who underwent both 4.5 and 6.0 imaging, 32 primary open-angle glaucoma eyes from 32 patients and 95 nonglaucoma eyes from 95 patients were studied. For the global region of 4.5 versus 6.0 scans, area under the curve was 0.940 and 0.916 for vessel area density (P=0.286); 0.941 and 0.921 for vessel skeleton density (P=0.385); 0.942 and 0.916 for flux (P=0.239); 0.912 and 0.884 for perfusion density (P=0.103); and 0.913 and 0.865 for FI (P=0.159), respectively. For the quadrant regions, 4.5 images significantly outperformed 6.0 images for the superior and inferior quadrants for flux and superior and nasal quadrants for FI (P-values=0.007, 0.047, 0.011, 0.007, respectively); other quadrant differences were not significant.

CONCLUSIONS

Parameters from 4.5 scans generally outperformed those from 6.0 scans in the global and quadrant regions, suggesting greater digital resolution in 4.5 scans of the immediate peripapillary RPC is important in detecting glaucomatous changes.

Functional and Structural Reliability of Optic Nerve Head Measurements in Healthy Eyes by Means of Optical Coherence Tomography Angiography

Background and Objectives: the aim of the study was to evaluate the repeatability and reproducibility of optical microangiography (OMAG)-based optical coherence tomography angiography (OCTA) in the optic nerve head (ONH) and radial peripapillary capillary (RPC) perfusion assessment of healthy eyes. Materials and Methods: in this observational study, a total of 40 healthy subjects underwent ONH evaluation, using an OMAG-based OCTA system at baseline (T₀), after 30 min (T₁), and after 7 days (T₂). The main outcome measures were the vessel density (VD) and flux index (FI) of the RPCs, as well as peri-papillary retinal nerve fibre layer (pRNFL) thickness. The analysis was performed by two observers independently. The coefficient of repeatability (CR), within the subject coefficient of variation (CVw) and intrasession correlation coefficient (ICC), to evaluate intrasession repeatability of measurements was calculated for each observer. Results: the high intrasession and intersession repeatability and reproducibility were assessed in the two observers for all three outcome measures. Of note, the CRs for the first and the second observer were 0.011 (95% confidence interval (CI) 0.009–0.014) and 0.016 (95% CI 0.013–0.020) for FI, 0.016 (95% CI 0.013–0.021) and 0.017 (95% CI 0.014–0.021) for VD, and 2.400 (95% CI 1.948–3.092) and 3.732 (95% CI 3.064–4.775) for pRNFL thickness, respectively. The agreement between them was excellent for pRNFL assessment and very good for FI and VD. Conclusion: OCTA has a great potential in the accurate assessment of ONH and peri-papillary microcirculation. It allows for repeated and reproducible measurements without multiple scans-related bias, thus guaranteeing an independent operator analysis with good reproducibility and repeatability.

Comparison of the Repeatability of Macular Vascular Density Measurements Using Four Optical Coherence Tomography Angiography Systems

The aim of this study was to compare the repeatability of optical coherence tomography angiography (OCT-A) measurements of macular vessel density using four OCT-A systems, including Heidelberg Spectralis HRA, Optovue RTVue XR, Zeiss Cirrus HD-OCT 5000, and Topcon DRI OCT Triton. A cross-sectional design was used for this study. The vascular density and vascular length density of the superficial and deep retinal capillary plexuses were imaged with OCT-A using 3 mm and 6 mm scan patterns and were calculated using ImageJ. Comparisons of intraclass correlation coefficients (ICC) were conducted. We found that the OCT-A systems had various levels of repeatability. Zeiss had better repeatability for vessel density than the other systems (overall ICC = 0.936). Optovue had better repeatability for vessel length density when the 6 mm scan pattern was used (ICC = 0.680 and 0.700 for retinal superficial and deep capillary plexus, respectively). We concluded that repeatability varied when different scan patterns of various OCT-A systems were used for imaging the superficial retinal and deep capillary plexuses. Results should be seen as valid only for a given method. The repeatability of various OCT-A systems should be considered in clinical practice and in clinical trials that use OCT-A metrics as outcome measures.

Quantitative evaluation of primary retinitis pigmentosa patients using colour Doppler flow imaging and optical coherence tomography angiography

PURPOSE

To find the potential relation between changes in retinal large vessels and terminal vessels using colour Doppler flow imaging (CDFI) and optical coherence tomography angiography (OCTA) and to compare the respective advantages of CDFI and OCTA in evaluating vascular changes in retinitis pigmentosa (RP) patients.

METHODS

A prospective series of case study was conducted to enrol RP patients and age-matched controls, who were, respectively, imaged by CDFI and OCTA. Repeatability and reproducibility of both CDFI and OCTA were performed among healthy volunteers. The central retinal artery (CRA) was detected by CDFI analysis to provide parameters of peak systolic velocity (PSV), end-diastolic velocity (EDV) and time-averaged maximum velocity (TAMV). Retinal parameters were evaluated from OCTA images, including vascular area density (VAD) of the superficial vascular layer, the fovea avascular zone (FAZ) area and retinal thickness. RP patients were separated into a high-vision group and a low-vision group, according to median vision (0.3, LogMAR 0.5). Multiple comparisons were used to analyse the data between groups. A correlation analysis was used to determine the correlation between CDFI and OCTA parameters.

RESULTS

Twenty RP patients (40 eyes) and thirteen normal volunteers (26 eyes) were enrolled in this study. Repeatability and reproducibility of the measurements by CDFI had higher CVs, from 4.5% to 15.4%, than those measurements by OCTA (<5%). All the CDFI and OCTA parameters examined had significant reductions in RP patients compared to those in the controls (p < 0.01). Compared to the high-vision group, the low-vision group exhibited a statistically significant decrease in vascular parameters of the FAZ area, fovea VAD and parafovea nasal side VAD (p < 0.05); as well as in the parameters of the fovea thickness, and the parafovea nasal, superior and inferior side thickness (p < 0.05). From the correlation analysis, a significant association was found between the vision and CDFI parameters (PSV and time-averaged maximum velocity (TAMX), p < 0.05), and the vision and OCTA parameters (FAZ area, fovea and nasal side VAD, retinal thickness in all sides, p < 0.05). PSV and TAMX of the CRA were closely related to the OCTA superficial VAD in all sides, whereas the CDFI parameters showed poor correlation with retinal thickness.

CONCLUSIONS

Colour Doppler flow imaging (CDFI) and OCTA parameters revealed a significant reduction in RP patients when compared to the controls. OCTA can detect vision-related microvascular and thickness changes around the macula between high- and low-vision groups, which happen earlier than the changes in large vessels. In addition to good repeatability and reproducibility, OCTA may have significant utility in the diagnosis and monitoring of disease progression in RP patients.

Retinal Microvascular Abnormalities in Children with Type 1 Diabetes Mellitus Without Visual Impairment or Diabetic Retinopathy

Purpose

To study the characteristics and associated factors of retinal microvascular abnormalities in children with type 1 diabetes mellitus (T1DM) without visual impairment and diabetic retinopathy (DR).

Methods

Case-control hospital-based study including children with or without DM. Optical coherence tomography angiography (OCTA; CIRRUS HD-OCT model 5000) was used to scan 6 × 6 mm square area of posterior retina and optic disc. The indexes analyzed mainly included vascular length density (VD), perfusion density (PD), and foveal avascular zone area, perimeter, and morphology. Independent risk factors were analyzed by multifactor linear regression.

Results

A total of 47 children with T1DM and 44 healthy subjects were enrolled. Statistical analysis showed that VD within 1 to 3 mm (inner ring) of the macula in the case group was smaller than that in the control group (18.561 ± 1.151/mm: 19.161 ± 0.464/mm; P< 0.001), and mother's excessive weight gain during pregnancy was an independent factor (P = 0.004); VD within 3 to 6 mm (outer ring) of the macula in the case group was smaller than that in the control group (19.044 ± 0.847/mm; 19.404 ± 0.496/mm, P = 0.029), while serum creatinine level was revealed to be an independent factor (P = 0.009); PD within 3 to 6 mm of the macula in the case group was higher than that in the control group (0.456 ± 0.015: 0.442 ± 0.030) (P = 0.003), with no independent factor observed in regression analysis.

Conclusion

Retinal microvasculopathy had already occurred in the parafoveal area of diabetic children without visual impairment and DR; early screening and close follow-up were recommended for children with high-risk factors.

Peripapillary Region Perfusion and Retinal Nerve Fiber Layer Thickness Abnormalities in Diabetic Retinopathy Assessed by OCT Angiography

Purpose

To quantify peripapillary region perfusion and retinal nerve fiber layer (RNFL) thickness abnormalities in different stages of diabetic retinopathy (DR) using optical coherence tomography angiography (OCTA).

Methods

Seventy-two eyes of 72 patients with diabetes were included as follows: 23 with no DR (No DR), 24 with mild-to-moderate nonproliferative DR (mild DR), 25 with severe nonproliferative to proliferative DR (severe DR), and 26 age-matched healthy controls. All eyes underwent a 4.5 × 4.5-mm rectangle scan centered on the optic nerve head. Vessel densities and RNFL thickness for the peripapillary area were calculated.

Results

A statistically significant decrease in vessel density was found in the peripapillary region with increased DR severity (all P < 0.001). There were significant correlations between DR severity and vessel density in the peripapillary region (P < 0.001), but not between DR severity and RNFL thickness (P > 0.05). There was a significantly positive correlation between vessel density and RNFL thickness of the peripapillary region in the mild DR group (r = 0.726, P < 0.001) but not in the no DR group (r = 0.008, P = 0.973) or the severe DR group (r = 0.281, P = 0.173).

Conclusions

Vessel density in the peripapillary region correlated significantly with DR severity, decreasing with DR aggravation. There was no obvious correlation observed between RNFL thickness and DR severity.

Translational Relevance

Vessel density in the peripapillary region, assessed by OCTA technology, can be potentially useful for analyzing and monitoring retinal nerve changes in DR patients.

Non-invasive measurement techniques for quantitative assessment of optic nerve head blood flow

Diseases of the optic nerve head involving changes in blood flow are common. However, the pathophysiology is not always fully understood. Several non-invasive methods for measuring optic nerve head blood flow are available, but currently no gold standard has been established. Methods for measuring blood flow in optic neuropathies including colour Doppler imaging, retinal function imager, optical coherence tomography angiography and laser speckle flowgraphy are reviewed. Ultrasound colour Doppler imaging is a fast measurement technique where several different parameters, especially the blood flow velocity, can be calculated. Though used for many years in ophthalmology, its use is not standardized and it requires significant observer skills. The retinal function imager is a direct method where the haemoglobin in erythrocytes is visualized and blood flow velocities in retinal vessels are calculated from a series of photos. The technique is not suitable for direct measurement of blood flow within the optic nerve head. Laser speckle flowgraphy uses a laser light which creates a light scatter pattern in the tissue. Particles moving in the area causes changes in the speckle pattern from which a relative blood flow can be estimated. It is, however, not known whether optic nerve head microcirculation is measurable with the technique. Optical coherence tomography angiography uses multiple scans to evaluate blood flow with good reproducibility but often problems with artefacts. The technique is continuously being refined and increasingly used in research as a tool for the study of blood flow in retinopathies and optic neuropathies. Most of the conducted studies are based on small sample sizes, but some of the methods show promising results in an optic nerve head blood flow research setting. Further and larger studies are required to provide standardized and comparable measurements before one or more of the methods can be considered clinical helpful in daily practice.

Quantification and Repeatability of Vessel Density and Flux as Assessed by Optical Coherence Tomography Angiography

Purpose

To determine the intrasession repeatability (test-retest variability) of parafoveal and peripapillary perfused capillary density (PCD) and normalized flux index (NFI) as assessed with Canon OCT-HS100 angiography.

Methods

Pairs of optical coherence tomography angiography (OCT-A) images were obtained from the parafoveal and peripapillary region of 30 eyes of 30 healthy subjects. PCD and NFI were calculated using generic image-processing software. Macular ganglion-cell complex thickness (GCC) and peripapillary retinal nerve fiber layer thickness (RNFLT) were also recorded. Bland-Altman analysis was performed and the coefficient of repeatability (CoR) and intraclass correlation coefficient (ICC) were calculated. Correlations of parafoveal PCD/NFI with GCC and of peripapillary PCD/NFI with RNFLT were also computed.

Results

Mean (standard deviation) parafoveal and peripapillary PCD were 40.0% (1.8%) and 44.5% (1.3%), respectively. Corresponding values for NFI were 151.2 (6.8) and 164.2 (3.9). For PCD, ICC was 0.76 for parafoveal and 0.79 for peripapillary measurements; corresponding CoRs were 2.7% and 1.8%. Corresponding values for NFI were 0.62 and 0.67 for ICC and 13.3 and 7.0 for CoR. Average measures ICC was 0.87/0.88 and 0.76/0.80 for the parafoveal/peripapillary PCD and NFI, respectively. PCD and NFI were weakly correlated with GCC (r = 0.39, P = 0.035; r = 0.33, P = 0.077) and moderately correlated with RNFLT (r = 0.43, P = 0.017; r = 0.55, P = 0.002).

Conclusions

Repeatability of a commercially available OCT-A with generic image-processing software was good (NFI) to excellent (PCD). Our results indicate that changes surpassing the variability in healthy subjects should be easily detectable in a clinical setting.

Translational Relevance

Repeatability estimates provide information regarding the relevance of changes in retinal perfusion.

Diurnal change of retinal vessel density and mean ocular perfusion pressure in patients with open-angle glaucoma

Purpose

To investigate, in primary open-angle glaucoma (POAG) and healthy subjects, the pattern and magnitude of diurnal variation in optical coherence tomography angiography (OCTA) retinal vessel density (RVD).

Design

Prospective, observational cross-sectional study.

Participants

A prospective study was conducted on 20POAG patients and 19 healthy subjects.

Methods

Peripapillary/macular RVD (using swept-source OCTA), intraocular pressure (IOP), and systemic blood pressure (BP) were measured five times a day (8 a.m., 11 a.m., 2 p.m.,5 p.m. and 8 p.m.). The magnitudes and patterns of diurnal changes in RVD, diastolic BP, and mean ocular-perfusion pressure (MOPP) were analyzed and compared between the POAG patients and the healthy subjects.

Main outcome measures

The patterns and magnitudes of diurnal RVD change in OCTA.

Results

Intra-visit repeatability (0.755–0.943) and inter-visit reproducibility (0.843–0.986) for the RVD measurements showed excellent reliability. In the POAG patients, the magnitude of diurnal change in peripapillary RVD (9.71±7.04%) and macular RVD (7.22±4.73%) were significantly greater than that in the healthy group (5.73±3.85%, P = 0.013 and 5.51±3.45%, P = 0.042, respectively). The magnitudes of diurnal variations of IOP and MOPP in the POAG group likewise were greater than those in the healthy group (P = 0.003 and 0.039). As for the patterns of diurnal RVD change, interestingly, at 8 p.m., the macular RVD of the healthy group increased to the highest level (44.12±2.95%) while that of the POAG group decreased to the lowest level (40.41±2.54%).

Conclusions

In POAG eyes, diurnal change of IOP, MOPP and RVD was significantly greater than in the healthy eyes. These findings suggest that diurnal RVD changes might reflect the hemodynamic variation of POAG.

Optic Nerve Head Perfusion Before and After Intravitreal Antivascular Growth Factor Injections Using Optical Coherence Tomography-based Microangiography

PURPOSE

To use optical coherence tomography angiography (OCTA) to evaluate the changes in optic nerve head perfusion following intravitreal antivascular endothelial growth factor injections.

METHODS

Preinjection and postinjection intraocular pressure (IOP) and OCTA images were taken of both the injected and uninjected fellow eyes.

RESULTS

Mean preinjection IOP was 16.6±4.7 mm Hg, which increased to a mean of 40.3±13.0 mm Hg (P<0.0001) during the first postinjection image and remained elevated at 36.1±11.5 mm Hg (P<0.0001) during the second postinjection image. Although no significant change was observed in flux, vessel area density, or normalized flux when comparing the OCTA preinjection and first postinjection images, a significant decrease at the second postinjection image was observed (P=0.03, 0.02, and 0.03, respectively). No significant change was observed in the uninjected fellow eye during the same time period (P=0.47, 0.37, and 0.38, respectively).

CONCLUSIONS

Following an antivascular endothelial growth factor injection, mean IOP increased significantly and OCTA imaging of the optic nerve demonstrated a mild but significant decrease in optic nerve head perfusion parameters. Clinicians performing these injections should be aware of these findings and monitor the status of the optic nerve in patients undergoing injections.

Diagnostic Performance of Macular Versus Peripapillary Vessel Parameters by Optical Coherence Tomography Angiography for Glaucoma

PURPOSE

To compare the diagnostic ability of the vessel parameters in macular and peripapillary regions measured using spectral-domain optical coherence tomography angiography (SD-OCTA) in differentiating primary open-angle glaucoma (POAG) from healthy eyes.

METHODS

POAG patients and healthy subjects underwent 6 × 6-mm scans centered on the macula and optic nerve head. Commercially available automatic segmentation created en face images from SD-OCTA of the superficial retinal layer (SRL) of the macular (m) and peripapillary (cp) regions. Vessel area density (VAD), vessel skeleton density (VSD), vessel complexity index (VCI), and flux were calculated. Area under curve (AUC) statistics controlled for age and intereye correlation.

RESULTS

Of 126 eyes from 79 patients who underwent SD-OCTA macula and peripapillary imaging, 50 eyes from 35 POAG patients and 37 healthy eyes from 25 control subjects had good quality imaging and were studied. Diagnostic accuracies of four perfusion parameters, VAD, VSD, VCI, and flux, were significantly greater in the peripapillary compared with the macular regions. For VAD, the cpAUC was 0.84 and mAUC was 0.73 (AUC difference: P = 0.026). For VSD, the cpAUC was 0.84 and mAUC was 0.72 (ΔP = 0.015). For VCI, the cpAUC was 0.80 and mAUC was 0.70 (ΔP = 0.045). For flux, the cpAUC = 0.87 and mAUC was 0.76 (ΔP = 0.0091).

CONCLUSIONS

Peripapillary perfusion parameters performed better than macular perfusion parameters for glaucoma diagnosis, supporting the idea that glaucomatous superficial retinal vascular changes are more pronounced in the peripapillary region.

TRANSLATIONAL RELEVANCE

The diagnostic accuracy of OCTA perfusion parameters of the superficial retinal microcirculation was greater for the peripapillary region than the macular region in the diagnosis of glaucoma.

A quantitative comparison of five optical coherence tomography angiography systems in clinical performance

AIM

To compare the clinical performance of 4 spectral-domain (SD) optical coherence tomography angiography (OCTA) systems: AngioVue™, AngioPlex™, Spectralis^® OCTA, AngioScan, and 1 swept-source (SS) OCTA SS OCT Angio™.

METHODS

Twenty-seven undilated right eyes of 27 participants underwent OCTA examination using five different systems respectively for both 3×3 and 6×6 mm² scan pattern (Spectralis OCTA for 3×3 mm² scan only). Image quality, including vessel valid visibility and the number of motion artifacts, and acquisition time were evaluated. Repeated measures analysis of variance (ANOVA) with Bonferroni's post-test and Friedman test with Dunn's post-test were used to compare measurements.

RESULTS

The age of the subjects was 28.19±5.55y (range, 23-49y). The spherical equivalent refraction was -2.55±1.84 D (range, 0.00 to -5.25 D). Significant difference was observed in the evaluation of vessel valid visibility (AngioVue the highest: 0.111±0.031 for 3×3 mm² scan and 0.128±0.020 for 6×6 mm² scan), number of motion artifacts (AngioVue the fewest: 0.778±1.086 for 3×3 mm² scan and 0.333±0.620 for 6×6 mm² scan) and acquisition time (AngioPlex the shortest: 8.537±1.921s for 3×3 mm² scan and 8.298±1.741s for 6×6 mm² scan; all P<0.001).

CONCLUSION

There is poor agreement of measurements among systems. AngioVue provides images with the highest vessel valid visibility and the fewest motion artifacts. AngioPlex achieves the shortest acquisition.

Noninvasive Assessment of Retinal Blood Flow Using a Novel Handheld Laser Speckle Contrast Imager

Purpose

We assessed the image quality and reproducibility of blood flow measurements from a novel handheld laser speckle imager in handheld and stabilized use cases.

Methods

Eleven dilated human subjects were imaged with the XyCAM Handheld Retinal Imager investigational device (XyCAM HRI) in the handheld and stabilized use case in nine consecutive imaging sessions. Subjects then underwent standard color fundus photography using a Topcon TRC 50DX. The vessel-to-background contrast of the XyCAM HRI red-free photo was compared to the fundus photograph, while the coefficient of variation of blood flow measurements in specific arteries and veins also was determined.

Results

Vessel-to-background contrast was statistically greater in the handheld use case when compared to the standard color fundus photographs (P = 0.01). Estimates of mean blood flow velocity (BFV) were highly correlated between the stabilized and handheld use case (r² = 0.96). Peak velocity estimates in arteries were significantly higher than those in veins (P < 0.05).

Conclusions

The XyCAM HRI prototype can acquire fundus photographs with the same or better level of clarity as color fundus photographs, and reproducibly acquire functional blood flow information in the handheld use case.

Translational Relevance

To our knowledge, this is the first human study of a handheld laser speckle retinal imaging device. Determination of retinal blood flow has applications to ophthalmic and systemic disease and a portable handheld retinal imager that determines blood flow may be widely adopted at the point of care.

OCT angiography findings in children with amblyopia

PURPOSE

To compare the microstructure and vascularity of amblyopic eyes in children with their contralateral eye and with eyes from control children using optical coherence tomography angiography (OCT-A).

METHODS

We conducted a prospective, cross-sectional evaluation of macular and optic disk vascular density and flow area using OCT-A (Avanti RTVue XR, Optovue Inc, Fremont, CA). Parameters were calculated using automated software.

RESULTS

A total of 52 children were included: 26 subjects with amblyopia and 26 nonamblyopic controls. The amblyopic eye of subjects showed a statistically significant decrease in macular vascular density (P = 0.0171) of the superficial capillary plexus (SCP), in the optic disk flow area (P = 0.0195) and in the average retinal nerve fiber layer thickness (P = 0.0194) as well as a marginally statistically significant decrease in the macular flow area of the SCP (P = 0.0305) and in the optic density (P = 0.0279). Compared with randomly selected eyes of controls, amblyopic eyes showed a statistically significant decrease in the macular flow area of the SCP (P = 0.005) and of the deep capillary plexus (DCP; P = 0.002), in the macula vascular density of the SCP (P = 0.022), in the optic disk flow area (P = 0.004), and a marginally statistical significant increase in the area of foveal avascular zone of the DCP (P = 0.038).

CONCLUSIONS

In our study cohort amblyopic eyes manifested significant differences in macular and optic disk vascularization. The clinical significance of these findings warrants further research.

Optic disc vessel density in nonglaucomatous and glaucomatous eyes: an enhanced-depth imaging optical coherence tomography angiography study

Purpose

To evaluate the ability of enhanced-depth imaging (EDI) optical coherence tomography angiography (OCTA) to detect vascular signals inside the glaucomatous optic disc.

Patients and methods

Ten glaucomatous eyes of 8 subjects and 11 nonglaucomatous eyes of 7 subjects underwent EDI and conventional OCTA for optic disc analysis. The optic disc vessel density (VD) at maximum scan depth (2 mm) was compared between the 2 methods and between glaucomatous and nonglaucomatous eyes. Regression analysis was used to determine the factors affecting disc VD.

Results

The median (25th, 75th percentile) of the visual field mean deviation was −20.5 (−25.1, −13.5) dB in glaucoma. The disc VD measured with the EDI method was significantly greater than that measured with the conventional method in glaucoma and nonglaucoma. The disc VD was also significantly lower in glaucoma than in nonglaucoma. The disc VD and mean deviation were significantly and positively correlated in both methods (conventional: R²=0.27, EDI: R²=0.22).

Conclusion

The correlation between disc VD and glaucoma severity was comparable between conventional and EDI measurements. Images obtained with EDI-OCTA have the additional benefit of revealing more vascular signals in deeper layers. The disc VD, as determined by both conventional and EDI-OCTA methods, may be an indicator of glaucoma severity.

Structural and Functional Associations of Macular Microcirculation in the Ganglion Cell-Inner Plexiform Layer in Glaucoma Using Optical Coherence Tomography Angiography

PURPOSE

To quantify retinal microvasculature within the macular ganglion cell-inner plexiform layer (GCIPL) in primary open-angle glaucoma (POAG) and normal eyes, determine association of vessel parameters with structural and functional measures, and report diagnostic accuracy of vessel parameters.

METHODS

POAG and normal patients underwent 6×6 mm macula scans [Angioplex optical coherence tomography angiography (OCTA); Cirrus HD-OCT 5000]; and Humphrey Field Analyzer II-i 24-2 visual field (VF). Prototype software performed semiautomatic segmentation to create GCIPL en face images, and quantified vessel area density (VAD), vessel skeleton density (VSD), and vessel complexity index (VCI) for the macula (globally, hemifields, and 6 focal sectors). Linear regression assessed association of OCTA parameters with VF mean deviation (MD) and GCIPL thickness globally and focally.

RESULTS

A total of 34 POAG and 21 normal eyes were studied. VAD, VSD, and VCI were reduced in POAG versus normal (0.463 vs. 0.486, P=0.00029; 0.230 vs. 0.219, P=0.0014; 1.15 vs. 1.09, P=0.0044, respectively), with a trend of worsening with increased POAG severity. Reduced global VF MD was associated with reduced VAD and VCI, controlling for age and intereye correlation (P=0.0060, 0.0080; R=0.205, 0.211). Both superior and inferior hemifield MD were associated with corresponding VAD, VSD, and VCI (all P<0.007; R ranged from 0.12 to 0.29). Global GCIPL thickness was not associated with global OCTA parameters, and only inferior sector GCIPL thickness was associated with corresponding VAD, VSD, and VCI (P<0.05; R ranged from 0.15 to 0.16). Area under curves for VAD, VSD, and VCI were fair to good (0.83, 0.79, 0.82; respectively; P<0.0001).

CONCLUSIONS

Glaucomatous eyes had reduced GCIPL microcirculation. OCTA parameters had stronger associations with functional rather than structural measures of glaucoma. This observation deserves further study.

Reproducibility of Optical Coherence Tomography Angiography Macular and Optic Nerve Head Vascular Density in Glaucoma and Healthy Eyes

PURPOSE

Optical coherence tomography angiography (OCT-A) is a noninvasive technology that allows visualization of retinal blood vessels. It is important to determine reproducibility of measurements as low precision can impair its diagnostic capabilities. The purpose of this study is to determine intravisit and intervisit reproducibility of optic nerve head (ONH) and macular vessel density measurements with OCT-A.

PATIENTS AND METHODS

Fifteen healthy volunteers and 14 glaucoma patients completed 2 OCT-A (AngioVue; Optovue Inc.) scanning sessions on each of 2 separate days to assess intravisit and intervisit reproducibility. A series of ONH and macula scans were acquired at each session. Vessel density (%), the proportion of vessel area over the total measurement area was calculated. Reproducibility was summarized using coefficients of variation (CV) and intraclass correlation coefficients calculated from variance component models.

RESULTS

In healthy eyes, the CV of intravisit and intervisit global vessel density measures ranged from 1.8% to 3.2% in ONH scans and 2.5% to 9.0% in macular scans. In glaucoma eyes, the CV of intravisit and intervisit global vessel density measures ranged from 2.3% to 4.1% in ONH scans and 3.2% to 7.9% in macular scans. CVs were lower for global than sectorial measures. Global OCT-A ONH intraclass correlation measurements for the retinal nerve fiber layer in healthy eyes were lower (range: 0.65 to 0.85) than in glaucoma eyes (range: 0.89 to 0.94). Scan size did not make large differences in measurement CVs.

CONCLUSIONS

Reproducibility of OCT-A ONH and macula vessel density measurements is good. Moreover, glaucoma patients have sparser vessel density with poorer reproducibility than healthy subjects.

Optical coherence tomography angiography: A comprehensive review of current methods and clinical applications

OCT has revolutionized the practice of ophthalmology over the past 10-20 years. Advances in OCT technology have allowed for the creation of novel OCT-based methods. OCT-Angiography (OCTA) is one such method that has rapidly gained clinical acceptance since it was approved by the FDA in late 2016. OCTA images are based on the variable backscattering of light from the vascular and neurosensory tissue in the retina. Since the intensity and phase of backscattered light from retinal tissue varies based on the intrinsic movement of the tissue (e.g. red blood cells are moving, but neurosensory tissue is static), OCTA images are essentially motion-contrast images. This motion-contrast imaging provides reliable, high resolution, and non-invasive images of the retinal vasculature in an efficient manner. In many cases, these images are approaching histology level resolution. This unprecedented resolution coupled with the simple, fast and non-invasive imaging platform have allowed a host of basic and clinical research applications. OCTA demonstrates many important clinical findings including areas of macular telangiectasia, impaired perfusion, microaneurysms, capillary remodeling, some types of intraretinal fluid, and neovascularization among many others. More importantly, OCTA provides depth-resolved information that has never before been available. Correspondingly, OCTA has been used to evaluate a spectrum of retinal vascular diseases including diabetic retinopathy (DR), retinal venous occlusion (RVO), uveitis, retinal arterial occlusion, and age-related macular degeneration among others. In this review, we will discuss the methods used to create OCTA images, the practical applications of OCTA in light of invasive dye-imaging studies (e.g. fluorescein angiography) and review clinical studies demonstrating the utility of OCTA for research and clinical practice.

Evaluation of Optical Coherence Tomography to Detect Elevated Intracranial Pressure in Children

Importance

Detecting elevated intracranial pressure in children with subacute conditions, such as craniosynostosis or tumor, may enable timely intervention and prevent neurocognitive impairment, but conventional techniques are invasive and often equivocal. Elevated intracranial pressure leads to structural changes in the peripapillary retina. Spectral-domain (SD) optical coherence tomography (OCT) can noninvasively quantify retinal layers to a micron-level resolution.

Objective

To evaluate whether retinal measurements from OCT can serve as an effective surrogate for invasive intracranial pressure measurement.

Design, Setting, and Participants

This cross-sectional study included patients undergoing procedures at the Children's Hospital of Philadelphia from September 2014 to June 2015. Three groups of patients (n = 79) were prospectively enrolled from the Craniofacial Surgery clinic including patients with craniosynostosis (n = 40). The positive control cohort consisted of patients with hydrocephalus and suspected intracranial hypertension (n = 5), and the negative control cohort consisted of otherwise healthy patients undergoing a minor procedure (n = 34).

Main Outcomes and Measures

Spectral-domain OCT was performed preoperatively in all cohorts. Children with cranial pathology, but not negative control patients, underwent direct intraoperative intracranial pressure measurement. The primary outcome was the association between peripapillary retinal OCT parameters and directly measured elevated intracranial pressure.

Results

The mean (SD) age was 34.6 (45.2) months in the craniosynostosis cohort (33% female), 48.9 (83.8) months in the hydrocephalus and suspected intracranial hypertension cohort (60% female), and 59.7 (64.4) months in the healthy cohort (47% female). Intracranial pressure correlated with maximal retinal nerve fiber layer thickness (r = 0.60, P ≤ .001), maximal retinal thickness (r = 0.53, P ≤ .001), and maximal anterior retinal projection (r = 0.53, P = .003). Using cut points derived from the negative control patients, OCT parameters yielded 89% sensitivity (95% CI, 69%-97%) and 62% specificity (95% CI, 41%-79%) for detecting elevated intracranial pressure. The SD-OCT measures had high intereye agreement (intraclass correlation, 0.83-0.93) and high intragrader and intergrader agreement (intraclass correlation ≥0.94). Conventional clinical signs had low sensitivity (11%-42%) for detecting intracranial hypertension.

Conclusions and Relevance

Noninvasive quantitative measures of the peripapillary retinal structure by SD-OCT were correlated with invasively measured intracranial pressure. Optical coherence tomographic parameters showed promise as surrogate, noninvasive measures of intracranial pressure, outperforming other conventional clinical measures. Spectral-domain OCT of the peripapillary region has the potential to advance current treatment paradigms for elevated intracranial pressure in children.

Optical Coherence Tomography Angiography of the Optic Disc; an Overview

Different diseases of the optic disc may be caused by or lead to abnormal vasculature at the optic nerve head. Optical coherence tomography angiography (OCTA) is a novel technology that provides high resolution mapping of the retinal and optic disc vessels. Recent studies have shown the ability of OCTA to visualize vascular abnormalities in different optic neuropathies. In addition, quantified OCTA measurements were found promising for differentiating optic neuropathies from healthy eyes.

Characterizing relationship between optical microangiography signals and capillary flow using microfluidic channels

Optical microangiography (OMAG) is a powerful optical angio-graphic tool to visualize micro-vascular flow in vivo. Despite numerous demonstrations for the past several years of the qualitative relationship between OMAG and flow, no convincing quantitative relationship has been proven. In this paper, we attempt to quantitatively correlate the OMAG signal with flow. Specifically, we develop a simplified analytical model of the complex OMAG, suggesting that the OMAG signal is a product of the number of particles in an imaging voxel and the decorrelation of OCT (optical coherence tomography) signal, determined by flow velocity, inter-frame time interval, and wavelength of the light source. Numerical simulation with the proposed model reveals that if the OCT amplitudes are correlated, the OMAG signal is related to a total number of particles across the imaging voxel cross-section per unit time (flux); otherwise it would be saturated but its strength is proportional to the number of particles in the imaging voxel (concentration). The relationship is validated using microfluidic flow phantoms with various preset flow metrics. This work suggests OMAG is a promising quantitative tool for the assessment of vascular flow.