Optical coherence tomography angiography of optic nerve head and parafovea in multiple sclerosis

Retinal Tissue Perfusion in Patients with Multiple Sclerosis

Purpose: The goal of this work was to determine whether the retinal tissue perfusion (RTP) is impaired in patients with multiple sclerosis (MS). Methods: Seventy-four patients [66 relapsing-remitting MS (RRMS) and 8 clinically isolated syndrome (CIS)] and 74 age- and gender-matched healthy controls were recruited. RTP was calculated as the retinal blood flow (measured using retinal function imager) supplying the macular area divided by the corresponding tissue volume of the inner retina from the inner limiting membrane to the outer plexiform layer, as measured by ultrahigh-resolution optical coherence tomography. Results: The RTP in the MS group was 2.37 ± 0.59 nl/s/mm³ (mean ± standard deviation), which was significantly lower than the control group (4.06 ± 0.89 nl/s/mm³, P < .001), reflecting a decrease of 42%. The blood flow volume was 2.50 ± 0.50 nl/s in MS, which was 45% lower than in the control group (4.56 ± 0.91 nl/s, P < .001). In addition, the tissue volume of the inner retina was significantly lower than in the control group (P < .05). The RTP in patients with MS was significantly correlated with the retinal blood flow volume (r = 0.84, P < .001) and retinal tissue volume (r = -0.56, P < .001). However, the retinal blood flow in patients with MS was not related to the tissue volume (r = -0.06, P = .59). Conclusions: Impaired retinal tissue perfusion occurred in patients with MS, which could be developed as a possible biomarker in monitoring disease progression in MS.

Macular vascular circulation and retinal oxygen saturation changes for idiopathic macular epiretinal membrane after vitrectomy

PURPOSE

To investigate the postoperative changes in retinal-choroidal blood flow area and retinal vascular oxygen saturation among patients with idiopathic macular epiretinal membranes (iERMs).

METHODS

This study prospectively included 24 eyes of 24 consecutive patients who underwent vitrectomy for iERMs. The flow area of choriocapillary layer, retinal superficial capillary plexuses (SCPs) and retinal deep capillary plexuses (DCPs) were performed using optical coherence tomography angiography with angiovue prototype software, and retinal vascular oxygen saturation was measured using retinal oximeter with the built-in software. The flow area of choriocapillary layers and mean retinal vessel oxygen saturation before and after surgery were compared.

RESULTS

Three months after vitrectomy, the foveal flow area of choriocapillary layer increased clinically significantly from 1.5 ± 0.2 to 1.6 ± 0.2 mm² (p = 0.02). The retinal vascular changes of SCPs and DCPs were not statistically significant. The mean retinal arterial oxygen saturation was 89.9 ± 11.3% preoperatively and increased to 94.5 ± 9.7% postoperatively (p = 0.04). Foveal retinal thickness revealed a clinically significant decrease from 547.8 ± 88.2 μm to 403.0 ± 47.5 μm after surgery (p < 0.05). Postoperative best corrected visual acuity had no statistically significant correlation with foveal flow area of the choriocapillary layer and retinal vascular oxygen saturation.

CONCLUSIONS

There was a decrease of retinal thickness, an improved flow area of choriocapillary layer in macular region, and an increase of retinal arterial vascular oxygen among iERMs patients after vitrectomy.

Ophthalmic, systemic, and genetic characteristics of patients with Wolfram syndrome

Purpose:

To evaluate the ophthalmic, systemic, and genetic characteristics of patients with Wolfram syndrome.

Methods:

In total, 13 patients with suspected or clinically diagnosed Wolfram syndrome underwent ophthalmic and systemic examinations and genetic analyses for Wolfram syndrome between August and October 2018.

Results:

The mean age of the subjects was 24.2 ± 7.1 years, of which 5 (38.5%) subjects were male and 8 (61.5%) were female. The mean best-corrected visual acuity ranged from counting fingers to 20/40, with a mean of 20/250 (1.10 ± 0.69 logarithm of the minimum angle of resolution). Dyschromatopsia was present in all patients (100%). There was a severe decrease in the average peripapillary retinal nerve fiber layer and macular ganglion cell–inner plexiform layer thicknesses (54.7 ± 6.5 and 51.9 ± 4.8 µm, respectively). Optical coherence tomography angiography showed significantly lower whole-image, inside disk, and peripapillary vessel densities in the patients with Wolfram syndrome than in the healthy controls (p < 0.001 for all). All patients who underwent genetic analyses had mutations in the WFS1 gene. Moreover, two novel mutations, p.Met623Trpfs*2 (c.1867delA) and p.Arg611Profs*9 (c.1832_11847del16) at exon 8, were detected. The frequency of systemic findings was as follows: optic atrophy (100%), diabetes mellitus (92.3%), central diabetes insipidus (38.5%), sensorineural hearing loss (38.5%), and presence of urological (30.8%), psychiatric (30.8%), and neurological (23.1%) diseases.

Conclusion:

Wolfram syndrome is a rare genetic disorder that can be associated with severe ophthalmic and systemic abnormalities. All patients who present with unexplained optic atrophy should be evaluated for Wolfram syndrome, even if they do not have diabetes mellitus because optic atrophy can sometimes manifest before diabetes mellitus.

Leber's hereditary optic neuropathy: Severe vascular pathology in a severe primary mutation

The purpose of the present article was to evaluate the previously unreported vascular alterations in Leber's Hereditary Optic Neuropathy (LHON) 3460 mitochondrial DNA (mtDNA) mutation. Among the three primary mtDNA mutations, namely 11778, 14484, and 3460, LHON 3460 is the most rare and historically recognized as having the poorest visual prognosis. Optical coherence tomography angiography (OCTA) is a novel imaging modaility providing high-resolution microcirculation maps and enhancing visualization of the optic disc and peripapillary capillary beds. We herein exploit the advantages of OCTA, for the first time, to assess the optic nerve head and peripapillary microvasculature changes in an affected patient and compare these vascular changes with an asymptomatic carrier for LHON 3460, serving as a control. Vascular changes in LHON 11778 and 14484 have classically shown microvasculature attenuation localized specifically to the temporal peripapillary quadrant. In the present case, however, OCTA in LHON 3460, the most severe of the three mutational subtypes, illustrated significant vascular attenuation involving the nasal peripapillary region in addition to the temporal peripapillary microvascular changes classically seen in LHON. Our findings suggest that vascular measures may serve useful for objectively assessing mitochondrial disease. Further OCTA studies involving the nasal peripapillary region may be warranted to further understand vascular pathogenesis in LHON.

What Does Optical Coherence Tomography Offer for Evaluating Physical Disability in Patients with Multiple Sclerosis?

Visual dysfunction is one of the most common clinical manifestations of multiple sclerosis (MS). For example, optic neuritis is the onset symptom in 20% of patients with MS. Visual pathway impairment presents in most patients with MS, including patients who have not experienced optic neuritis. During the last decade, many clinical trials of MS have included visual outcomes. One tool used in these studies, optical coherence tomography, is a non-contact, noninvasive, high-resolution optical imaging technology that helps segmentation and measurement of specific retinal layers using computerized algorithms. Optical coherence tomography is used in various stages of MS from diagnosis to treatment of the disease. In this review, we summarize the use of optical coherence tomography in MS and study its usefulness for evaluating the physical disabilities of MS patients.

Image Artifacts in Optical Coherence Tomography Angiography Among Patients With Multiple Sclerosis

PURPOSE

To evaluate artifacts in optical coherence tomography angiography (OCT-A) images of multiple sclerosis (MS) patients and healthy controls.

MATERIALS AND METHODS

This was a prospective cross-sectional study conducted at the Department of Neurology and the Wilmer Eye Institute at Johns Hopkins Hospital. Subjects included patients with an established diagnosis of MS and healthy volunteers. OCT-A was performed using Spectralis® OCT-A prototype, OCT2 (Heidelberg, Germany). The type and frequency of artifacts, the clinical factors associated with them, and their impact on vessel density measurements were assessed.

RESULTS

Overall, 385 images from 102 participants were analyzed. The majority of images (97.1%) had some degree of artifact. The most frequent was motion artifact (96.3%), followed by blinking (51.9%), and loss of focus (25.1%). MS patients were more likely to have any artifact vs. controls (OR [95% CI], 3.83 [1.12-12.92]), and were more likely to have motion artifacts with longer disease duration (OR [95% CI], 1.11 [1.03-1.20]) or history of optic neuritis (OR [95% CI], 4.24 [1.19-15.16]). The relative area occupied by the artifact was found to underestimate vessel density measurements in both MS patients and controls.

CONCLUSIONS

Artifacts are common with OCT-A imaging using this particular Spectralis® OCT-A prototype and can impact quantitative vascular density metrics. Future studies should review images for artifacts before drawing definitive conclusions.

Functional and morphological changes of the retinal vessels in Alzheimer's disease and mild cognitive impairment

Imaging and histopathological studies have demonstrated that structural changes of the retina affect subjects with Alzheimer’s disease (AD) or mild cognitive impairment (MCI). The aim of this study was to quantitatively investigate the retinal vessels in these disorders, using dynamic vessel analyzer (DVA) and optical coherence tomography angiography (OCTA) analysis. Twelve subjects with AD, 12 subjects with MCI, and 32 gender- and age-matched controls were prospectively enrolled. Mean ± SD age was 72.9 ± 7.2 years in the AD group, 76.3 ± 6.9 years in the MCI group, and 71.6 ± 5.9 years in the control group (p = 0.104). In the DVA dynamic analysis, the arterial dilation was decreased in the AD group (0.77 ± 2.06%), in the comparison with the control group (3.53 ± 1.25%, p = 0.002). The reaction amplitude was decreased both in AD (0.21 ± 1.80%, <0.0001) and MCI (2.29 ± 1.81%, p = 0.048) subjects, compared with controls (3.86 ± 1.94%). OCTA variables did not differ among groups. In the Pearson correlation analysis, amyloid β level in the cerebrospinal fluid was directly correlated with the arterial dilation (R = 0.441, p = 0.040) and reaction amplitude (R = 0.580, p = 0.005). This study demonstrate that Alzheimer’s and MCI subjects are characterized by a significant impairment of the retinal neurovascular coupling. This impairment is inversely correlated with the level of amyloid β in the cerebrospinal fluid.

Novel uses of retinal imaging with optical coherence tomography in multiple sclerosis

Introduction: Multiple Sclerosis (MS) is the most common chronic autoimmune neuroinflammatory condition in young adults. It is often accompanied by optic neuritis (ON) and retinal neuro-axonal damage causing visual disturbances. Optical coherence tomography (OCT) is a sensitive non-invasive method for quantifying intraretinal layer volumes. Recently, OCT not only showed to be a reliable marker for ON-associated damage, but also proved its high prognostic value for functional outcome and disability accrual in patients with MS. Consequently, OCT is discussed as a potential marker for monitoring disease severity and therapeutic response in individual patients. Areas covered: This article summarizes our current understanding of structural retinal changes in MS and describes the future potential of OCT for differential diagnosis, monitoring of the disease course and for clinical trials. Expert commentary: Today, OCT is used in clinical practice in specialized MS centers. Standardized parameters across devices are urgently needed for supporting clinical utility. Novel parameters are desirable to increase sensitivity and specificity in terms of MS.

Future clinical applicability of optical coherence tomography angiography

Optical coherence tomography angiography (OCT-A) is an emerging technology that allows for the non-invasive imaging of the ocular microvasculature. Despite the wealth of observations and numerous research studies illustrating the potential clinical uses of OCT-A, this technique is currently rarely used in routine clinical settings. In this review, technical and clinical aspects of OCT-A imaging are discussed, and the future clinical potential of OCT-A is considered. An understanding of the basic principles and limitations of OCT-A technology will better inform clinicians of its future potential in the diagnosis and management of ocular diseases.

Optical coherence tomography angiography of the macula and optic nerve head: microvascular density and test-retest repeatability in normal subjects

Background

Despite the potential usefulness of optical coherence tomography angiography in retinal and optic disc conditions, the reliability of the imaging modality remains unclear. This study set out to measure the microvascular density of macula and optic disc by mean of optical coherence tomography angiography and report the repeatability of the vessel density measurements.

Methods

Cross sectional observational cohort study. Subjects with normal eyes were recruited. Two sets of optical coherence tomography angiography images of macula and optic nerve head were acquired during one visit. Novel in-house developed software was used to count the pixels in each images and to compute the microvessel density of the macula and optic disc. Data were analysed to determine the measurement repeatability.

Results

A total of 176 eyes from 88 consecutive normal subjects were recruited. For macular images, the mean vessel density at superficial retina, deep retina, outer retina and choriocapillaries segment was OD 0.113 and OS 0.111, OD 0.239 and OS 0.230, OD 0.179 and OS 0.164, OD 0.237 and OS 0.215 respectively. For optic disc images, mean vessel density at vitreoretinal interface, radial peripapillary capillary, superficial nerve head and disc segment at the level of choroid were OD 0.084 and OS 0.085, OD 0.140 and OS 0.138, OD 0.216 and OS 0.209, OD 0.227 and OS 0.236 respectively. The measurement repeatability tests showed that the coefficient of variation of macular scans, for right and left eyes, ranged from 6.4 to 31.1% and 5.3 to 59.4%. Likewise, the coefficient of variation of optic disc scans, for right and left eyes, ranged from 14.3 to 77.4% and 13.5 to 75.3%.

Conclusions

Optical coherence tomography angiography is a useful modality to visualise the microvasculature plexus of macula and optic nerve head. The vessel density measurement of macular scan by mean of optical coherence tomography angiography demonstrated good repeatability. The optic disc scan, on the other hand, showed a higher coefficient of variation indicating a lower measurement repeatability than macular scan. Interpretation of optical coherence tomography angiography should take into account test-retest repeatability of the imaging system.

Trial registration

National Healthcare Group Domain Specific Review Board (NHG DSRB) Singapore. DSRB Reference: 2015/00301.

Electronic supplementary material

The online version of this article (10.1186/s12886-018-0976-y) contains supplementary material, which is available to authorized users.

OCT Angiography: A Technique for the Assessment of Retinal and Optic Nerve Diseases in the Pediatric Population

Optical coherence tomography angiography (OCT-A) is a novel, rapidly evolving, non-invasive imaging technique that allows images of the retinal vasculature to be obtained in a few seconds. Blood vessels of different retinal vascular plexuses and the foveal avascular zone (FAZ) can be examined without the administration of any contrast or dye. Due to these characteristics, OCT-A could be an excellent complementary test to study retinal vascularization in children. Until now, most of the studies with OCT-A have been conducted in adults and only a few have been carried out in children. In this review, we describe the principles and advantages of OCT-A over traditional imaging methods and provide a summary of the OCT-A findings in retinopathy of prematurity and other retinal and optic disc pathologies in children. In view of the promising results from studies, the advantages of a relatively rapid and non-invasive method to assess the retinal vasculature makes OCT-A a tool of which applications in the field of pediatric ophthalmology will be expanded in the near future for patient diagnosis and follow-up in every day clinical practice.

Principles of OCTA and Applications in Clinical Neurology

PURPOSE OF REVIEW

The article reviews the recent findings on the use of optical coherence tomography angiography (OCTA) in neurology.

RECENT FINDINGS

OCTA is a new addition to the powerful and complementary technology of the OCT. Due to its noninvasiveness, and reproducibility, it is possible to obtain high-resolution 3D images of the vessels of the human eye. As the vessels of the retina with the presence of endothelial cell's tight junctions resemble the brain vessels, it was hypothesized that the imaging of the retinal vessels might bring insight into brain vessels. OCTA has been effectively used to predict retinal vessel abnormalities in dementia, demyelization, optic disc neuropathies, and inherited degenerative diseases. Most common findings were decrease of vascular density and flow and an increase of avascular zones. Although OCTA is a relative new technology, recent studies show that it can be successfully applied in neurology.

Peripapillary and parafoveal vascular network assessment by optical coherence tomography angiography in aquaporin-4 antibody-positive neuromyelitis optica spectrum disorders

BACKGROUND/AIMS

Current understanding of the alterations in the retinal vascular network in neuromyelitis optica spectrum disorders (NMOSDs) is limited. We aim to assess the peripapillary and parafoveal vessel density in aquaporin-4 antibody-positive NMOSD patients by optical coherence tomography (OCT) angiography.

METHODS

A total of 55 aquaporin-4 antibody-positive NMOSD patients with or without a history of optic neuritis (ON) and 33 healthy controls underwent spectral domain OCT and OCT angiography. Clinical histories, Expanded Disability Status Scale score, visual functional system score (VFSS) and disease duration were collected.

RESULTS

Peripapillary and parafoveal vessel density was significantly decreased in NMOSD eyes with or without a history of ON. The decrease in retinal vessel density could occur before ON and retinal nerve fibre layer (RNFL) atrophy. Peripapillary vessel density correlated well with the spectral domain OCT measurements and VFSS in NMOSD eyes with a history of ON.

CONCLUSION

Subclinical primary retinal vasculopathy may occur in NMOSD prior to ON and RNFL atrophy. Peripapillary vessel density might be a sensitive predictor of visual outcomes in NMOSD patients with ON.

Optical Coherence Tomography Angiography in Optic Disc Swelling

PURPOSE

To compare optical coherence tomography angiography (OCT-A) of peripapillary total vasculature and capillaries in patients with optic disc swelling.

DESIGN

Cross-sectional study.

METHODS

Twenty nine eyes with acute nonarteritic anterior ischemic optic neuropathy (NAION), 44 eyes with papilledema, 8 eyes with acute optic neuritis, and 48 eyes of normal subjects were imaged using OCT-A. Peripapillary total vasculature information was recorded using a commercial vessel density map. Customized image analysis with major vessel removal was also used to measure whole-image capillary density and peripapillary capillary density (PCD).

RESULTS

Mixed models showed that the peripapillary total vasculature density values were significantly lower in NAION eyes, followed by papilledema eyes and control eyes, using commercial software (P < .0001 for all comparisons). The customized software also showed significantly lower PCD of NAION eyes compared with papilledema eyes (all P < .001), but did not show significant differences between papilledema and control subjects. Our software showed significantly lower whole image and PCD in eyes with optic neuritis than papilledema. There was no significant difference between NAION and optic neuritis using our software. The area under the receiver operating curves for discriminating NAION from papilledema eyes and optic neuritis from papilledema eyes was highest for whole-image capillary density (0.94 and 0.80, respectively) with our software, followed by peripapillary total vasculature (0.9 and 0.74, respectively) with commercial software.

CONCLUSIONS

OCT-A is helpful to distinguish NAION and papillitis from papilledema. Whole-image capillary density had the greatest diagnostic accuracy for differentiating disc swelling.

Optical coherence tomography angiography at the acute phase of optic disc edema

Background

The differential diagnosis of optic disc edema at the acute phase can be challenging. OCT angiography (OCTA) is a new technology allowing the visualization of the peripapillary vascular network and optic disc capillaries. The peripapillary network alterations of glaucoma and chronic non-arteritic anterior ischemic optic neuropathy (NAION) were reported. However, no OCTA studies on acute optic disc edema from various causes. The aim of this project was to use OCTA to demonstrate the vascular changes the optic nerve head of various types of optic disc edema at the acute phase.

Methods

In this retrospective study, patients with non-arteritic anterior ischemic optic neuropathy (NAION), papillitis or papilledema were recruited. Each patient was imaged using the AngioPlex™ CIRRUS™ HD-OCT device(model 5000, Carl Zeiss Meditec, Inc., Dublin, USA) with a scanning area of 6 × 6 mm² centered on the optic disc. A morphological analysis of the peripapillary network was performed. For some patients with unilateral optic disc edema, a quantitative analysis was performed using a swept-source OCT-A system (PLEX® Elite 9000, Carl Zeiss Meditec, Inc., Dublin, USA). Vessel perfusion density and flux index of the peripapillary area were calculated.

Results

Eight eyes with NAION (4 patients), 12 eyes with papillitis (6 patients) and 25 eyes with papilledema (13 patients) were imaged. The apparent disappearance or moderate pattern alteration of the peripapillary capillary vessels were observed in patients with NAION or papillitis, respectively. For papilledema, the capillaries at the surface of the optic disc were dilated and tortuous, but no peripapillary network pattern changes were observed. The quantitative analysis did not show any difference of peripapillary network between NAION and healthy eyes. For papillitis, the flux index was higher in inflammatory eyes compared to the healthy eyes in average (p = 0.03).

Conclusion

At the acute phase, the morphological analysis of OCT-A appeared to be more useful than the quantification analysis, facilitating the differentiation between the three kinds of ONH edema: ischemic, inflammatory and papilledema.

Peripapillary vessel density changes in Leber's hereditary optic neuropathy: a new biomarker

IMPORTANCE

The contribution of the microvascular supply to the pathogenesis of Leber's hereditary optic neuropathy (LHON) is poorly understood.

BACKGROUND

We aimed at measuring the peripapillary capillary vessel density (VD) using optical coherence tomography angiography (OCT-A) at different stages of LHON.

DESIGN

Prospective, cross-sectional, multicenter, observational study.

PARTICIPANTS

Twenty-two LHON patients divided in four groups: unaffected mutation carriers (LHON-u); early sub-acute stage (LHON-e); late sub-acute stage (LHON-l); chronic stage (LHON-ch).

METHODS

OCT-A scans centred on the optic disc were obtained by spectral domain OCT system.

MAIN OUTCOME MEASURES

VD, retinal nerve fibre layer (RNFL) and ganglion cell-inner plexiform layer (GC-IPL) thickness were compared between groups.

RESULTS

Significant VD changes were detected in every sector (P < 0.0001). In LHON-e, the VD was reduced in the temporal sector compared with LHON-u and in the temporal and inferotemporal sectors compared with controls. In LHON-l, VD was reduced in whole, temporal, superotemporal and inferotemporal sectors compared with LHON-u and controls. In LHON-ch, the VD was reduced in all sectors compared to the other groups. An asynchronous pattern emerged in the temporal sector with VD changes occurring earlier than RNFL thickness changes and together with GC-IPL thinning.

CONCLUSIONS AND RELEVANCE

Significant peripapillary miscrovascular changes were detected over the different stages of LHON. Studying the vascular network separately from fibres revealed that microvascular changes in the temporal sector preceded the changes of RNFL and mirrored the GC-IPL changes. Measurements of the peripapillary vascular network may become a useful biomarker to monitor the disease process, evaluate therapeutic efficacy and elucidate pathophysiology.

Optical coherence tomography angiography in retinal vein occlusions

PURPOSE

To examine the vascular density in different retinal layers and in the choriocapillaris in eyes with retinal vein occlusions (RVO).

METHODS

Applying optical coherence tomography angiography (OCTA), we examined patients with unilateral RVOs and normal individuals of a control group.

RESULTS

The study group included 48 patients with unilateral RVO and the control group 17 normal individuals. Eyes affected by RVO as compared to the contralateral unaffected eyes (all P < 0.001), and the contralateral unaffected eyes as compared to the eyes of the control group (P < 0.05), showed a lower vessel density in the superficial and deep retinal layers in all regions except for the foveal region. Choriocapillaris density was lower (P < 0.001), foveal retinal thickness and subfoveal choroidal thickness (P < 0.001) were thicker, and the foveal avascular zone was larger (P = 0.003) in the RVO eyes than in the contralateral eyes. For 29 eyes undergoing OCTA and fluorescein angiography, two examiners independently rated the retinas to be ischemic in fluorescein angiography in 14 eyes and in OCTA in 9 of these 14 eyes.

CONCLUSIONS

Upon OCTA, unaffected eyes of patients with unilateral RVOs showed vascular abnormalities in the superficial and deep retinal layers when compared to those of healthy individuals.

Macular choroidal thickness and peripapillary retinal nerve fiber layer thickness in normal adults and patients with optic atrophy due to acute idiopathic demyelinating optic neuritis

Purpose

To evaluate the association between macular choroidal thickness and peripapillary RNFL thickness in patients with optic atrophy due to acute idiopathic demyelinating optic neuritis and in normal controls using spectral domain optical coherence tomography (SD-OCT).

Methods

We performed SD-OCT peripapillary RNFL circular scan centered on the optic disc with horizontal and vertical crosshair scans through the fovea using the enhanced depth technique in 62 eyes with optic atrophy due to acute idiopathic demyelinating optic neuritis and 86 eyes of normal controls. The association between RNFL thickness and macular choroidal thickness measurements was assessed.

Results

The mean age was 43 ± 14 years (mean ± SD) in patients with optic atrophy and 45 ± 16 years in healthy controls (p = 0.791). There was a significant association between nasal peripapillary RNFL thickness and choroidal thickness at 3.0 mm nasal to the foveal center in patients with optic atrophy in multivariate analysis (estimate = 1.398, p = 0.011). In controls, there were significant associations between global average, superior, and inferior peripapillary RNFL thickness and choroidal thickness at 3.0 mm superior to the foveal center (estimate = -60.112, p = 0.044, estimate = 15.821, p = 7.312, and estimate = 15.203, p = 7.222, respectively).

Conclusions

Our SD-OCT data revealed that there was a significant association between peripapillary RNFL thickness and macular choroidal thickness in patients with optic atrophy due to acute idiopathic demyelinating optic neuritis and in controls, although the mechanism remained unclear. The difference in the pattern of association between patients with optic atrophy and controls suggests that optic atrophy caused by acute idiopathic demyelinating optic neuritis could affect the pattern of association between peripapillary RNFL thickness and macular choroidal thickness.

Quantification of macular perfusion using optical coherence tomography angiography: repeatability and impact of an eye-tracking system

BACKGROUND

The aim of the study was to evaluate the impact of integration of the eye-tracking system (ET) on the repeatability of flow density measurements using optical coherence tomography (OCT) angiography.

METHODS

20 healthy subjects were included in this study. OCT-angiography was performed using RTVue XR Avanti (Optovue Inc., Fremont, California, USA). The macula was imaged using a 3 × 3 mm scan twice with and twice without activation of the ET. Flow density data of the macular in the superficial and deep OCT angiograms were extracted and analyzed.

RESULTS

The difference between the flow density (whole en face) in the first session and second session with and without ET was statistically non-significant (with ET: superficial retinal OCT angiogram: p = 0.50; deep retinal OCT angiogram: p = 0.89; without ET: superficial retinal OCT angiogram: p = 0.81; deep retinal OCT angiogram: p = 0.24). There was no significant difference in the coefficients of repeatability for measurements with and without ET in the superficial retinal OCT angiogram (adjusted p-value = 0.176), whereas the difference was significant for the deep retinal OCT angiogram (adjusted p-value = 0.008).

CONCLUSIONS

Integration of the ET improved the repeatability of flow density measurements in the deep OCT angiogram; this needs to be considered when evaluating the long-term changes of flow density and when comparing data of different studies and different devices.

Emerging Applications of Optical Coherence Tomography Angiography (OCTA) in neurological research

Purpose

To review the clinical and research value of optical coherence tomography angiography (OCTA) in the field of neurology.

Methods

Current literature involving OCTA were reviewed through PubMed using the search terms “optical coherence tomography angiography”, with “multiple sclerosis”, “Alzheimer’s disease”, “optic neuropathy”, or other closely-related terms.

Results

OCTA has been applied in research to advance our understanding of the pathobiology of neurological disorders. OCTA-derived blood flow and vessel density measures are altered in multiple sclerosis (MS), Alzheimer’s disease (AD), and various optic neuropathies (ON) in varying regions of the posterior segment vasculature of the eye. These emerging research findings support the occurrence of retinal vascular alterations across a host of neurological disorders and raise the possibility that vasculopathy can be clinically relevant since it contributes to the pathobiology of several neurological disorders.

Conclusion

OCTA may be beneficial for neurological research. Additional investigations using OCTA in neurological disorders will help to further validate its clinical and research utilities in terms of characterizing the role of vasculopathy in neurological disorders.

Optical coherence tomography angiography

Optical coherence tomography (OCT) was one of the biggest advances in ophthalmic imaging. Building on that platform, OCT angiography (OCTA) provides depth resolved images of blood flow in the retina and choroid with levels of detail far exceeding that obtained with older forms of imaging. This new modality is challenging because of the need for new equipment and processing techniques, current limitations of imaging capability, and rapid advancements in both imaging and in our understanding of the imaging and applicable pathophysiology of the retina and choroid. These factors lead to a steep learning curve, even for those with a working understanding dye-based ocular angiography. All for a method of imaging that is a little more than 10 years old. This review begins with a historical account of the development of OCTA, and the methods used in OCTA, including signal processing, image generation, and display techniques. This forms the basis to understand what OCTA images show as well as how image artifacts arise. The anatomy and imaging of specific vascular layers of the eye are reviewed. The integration of OCTA in multimodal imaging in the evaluation of retinal vascular occlusive diseases, diabetic retinopathy, uveitis, inherited diseases, age-related macular degeneration, and disorders of the optic nerve is presented. OCTA is an exciting, disruptive technology. Its use is rapidly expanding in clinical practice as well as for research into the pathophysiology of diseases of the posterior pole.

An overview of the clinical applications of optical coherence tomography angiography

Optical coherence tomography angiography (OCTA) has emerged as a novel, non-invasive imaging modality that allows the detailed study of flow within the vascular structures of the eye. Compared to conventional dye angiography, OCTA can produce more detailed, higher resolution images of the vasculature without the added risk of dye injection. In our review, we discuss the advantages and disadvantages of this new technology in comparison to conventional dye angiography. We provide an overview of the current OCTA technology available, compare the various commercial OCTA machines technical specifications and discuss some future software improvements. An approach to the interpretation of OCTA images by correlating images to other multimodal imaging with attention to identifying potential artefacts will be outlined and may be useful to ophthalmologists, particularly those who are currently still unfamiliar with this new technology. This review is based on a search of peer-reviewed published papers relevant to OCTA according to our current knowledge, up to January 2017, available on the PubMed database. Currently, many of the published studies have focused on OCTA imaging of the retina, in particular, the use of OCTA in the diagnosis and management of common retinal diseases such as age-related macular degeneration and retinal vascular diseases. In addition, we describe clinical applications for OCTA imaging in inflammatory diseases, optic nerve diseases and anterior segment diseases. This review is based on both the current literature and the clinical experience of our individual authors, with an emphasis on the clinical applications of this imaging technology.

Comparison of Optical Coherence Tomography Angiography and Laser Speckle Flowgraphy for the Diagnosis of Normal-Tension Glaucoma

Purpose

To compare optical coherence tomography angiography (OCT-A) and laser speckle flowgraphy (LSFG) for the diagnosis of normal-tension glaucoma (NTG).

Methods

Twenty-eight eyes of 28 patients with NTG and 25 eyes of 25 normal subjects matched for age, refractive errors, systemic blood pressure, and central corneal thickness were evaluated. OCT-A was used to measure whole image vessel density, inside disc vessel density, and peripapillary vessel density; using LSFG, mean blur rate (MBR) inside the whole optic nerve head (ONH) area (MBR_A), and MBR of the vessel area (MBR_V) and tissue area (MBR_T) inside the ONH, were determined. Receiver operating characteristic (ROC) curves and areas under the ROC (AUROC) were used to assess the diagnostic ability of each variable.

Results

The AUROC for OCT-A whole image vessel density (0.950) was significantly greater than that for OCT-A peripapillary vessel density (0.830) and for all LSFG parameters (MBR_A = 0.793, MBR_V = 0.601, and MBR_T = 0.61) (P < 0.001). The AUROC for OCT-A inside disc vessel density (0.931) was significantly greater than that for all LSFG parameters (P < 0.005).

Conclusions

OCT-A vessel density had a higher glaucoma diagnostic ability compared to all LSFG parameters in patients with NTG.

Peripapillary vascular changes in radiation optic neuropathy: an optical coherence tomography angiography grading

AIMS

To investigate peripapillary vascular changes secondary to radiation optic neuropathy (RON) using optical coherence tomography angiography (OCT-A) and to propose a clinical grading of RON based on OCT-A findings.

METHODS

Thirty-four patients affected by RON were consecutively included. Each patient underwent best corrected visual acuity measurement (ETDRS score) and OCT-A (Nidek RS-3000 Advance device, Nidek, Gamagori, Japan). The radial peripapillary capillary plexus (RPCP) and the entire peripapillary capillary bed (EPCB) were analysed. Quantitative analysis of the OCT-A images was performed using open-source available ImageJ software (National Institutes of Health, Bethesda, Maryland, USA). Qualitative analysis based on the proposed clinical grading (Grades 0-4) was also performed by two masked graders.

RESULTS

RON clinical (qualitative) classification based on RPCP correlated with the quantitative RPCP perfusion analysis (P=0.0001). RON clinical classification based on RPCP statistically correlated with ETDRS score (P=0.001). RON clinical classification based on EPCB also correlated with the quantitative EPCB perfusion analysis and ETDRS score (P=0.02 and P=0.01, respectively). Compared with the clinical classification based on EPCB, the qualitative classification based on RPCP reached a higher intergrader agreement (0.96 and 0.86, respectively).

CONCLUSION

OCT-A can be used to detect RPCP abnormalities and to clinically classify RON with a high interexaminer agreement. The proposed clinical classification is supported by the quantitative analysis based on the use of specific images elaboration techniques and correlates with visual acuity of the examined eyes.

Retinal Vascular and Neural Remodeling Secondary to Optic Nerve Axonal Degeneration: A Study Using OCT Angiography

PURPOSE

To investigate the pathophysiologic interrelations between retinal neural and vascular changes, detected by spectral-domain OCT (SD-OCT) and OCT angiography (OCTA), resulting from optic nerve axonal degeneration.

DESIGN

Institutional, observational, case-control study with prospective enrollment.

PARTICIPANTS

Twenty-six patients affected by optic nerve axonal degeneration secondary to posterior optic pathway glioma (OPG) involving the chiasma, the postchiasmatic visual pathway, or both (but not involving optic nerves) and 24 gender- and age-matched healthy participants were included consecutively.

METHODS

Best-corrected visual acuity (Early Treatment Diabetic Retinopathy Study score) was measured and SD-OCT (Heidelberg Engineering, Heidelberg, Germany) and OCTA (Nidek RS-3000 Advance device; Nidek, Gamagori, Japan) were performed.

MAIN OUTCOME MEASURES

Peripapillary retinal nerve fiber layer (pRNFL), macular ganglion cell complex (GCC), and inner nuclear layer (INL) were analyzed using SD-OCT. The radial peripapillary capillary plexus, full-thickness peripapillary retina vascularization, and the macular superficial plexus (SCP) and deep capillary plexus (DCP) were analyzed using OCTA.

RESULTS

Peripapillary retinal nerve fiber layer and GCC thickness were reduced in eyes affected by OPG (P < 0.0001). Radial peripapillary capillary plexus perfusion also was reduced, as well as full-thickness peripapillary retina vascularization (P < 0.01 and P < 0.05, respectively). Macular DCP perfusion was reduced in eyes affected by OPG, whereas macular SCP perfusion did not differ between the 2 groups (P < 0.05 and P > 0.05, respectively). Global pRNFL thickness reduction correlated with the reduction of peripapillary perfusion (P < 0.01). Macular GCC thickness reduction did not correlate with SCP reduction (P > 0.05). The reduction of macular DCP perfusion did not correlate with inner nuclear layer thickness (P > 0.05).

CONCLUSIONS

Retinal neural remodeling secondary to optic nerve axonal degeneration resulting from OPG located at or posterior to the chiasm is accompanied by a secondary retinal vascular remodeling involving not only the peripapillary area, but also the macular area (DCP).

Optical coherence tomography angiography indicates associations of the retinal vascular network and disease activity in multiple sclerosis

BACKGROUND

Patients with multiple sclerosis (MS) and clinically isolated syndrome (CIS) may show alterations of retinal layer architecture as measured by optical coherence tomography. Little is known about changes in the retinal vascular network during MS.

OBJECTIVE

To characterize retinal vessel structures in patients with MS and CIS and to test for associations with MS disease activity.

METHOD

In all, 42 patients with MS or CIS and 50 healthy controls underwent retinal optical coherence tomography angiography (OCT-A) with analysis of the superficial and deep vascular plexuses and the choriocapillaries. We tested OCT-A parameters for associations with retinal layer volumes, history of optic neuritis (ON), and the retrospective disease activity.

RESULTS

Inner retinal layer volumes correlated positively with the density of both the superficial and deep vascular plexuses. Eyes of MS/CIS patients with a history of ON revealed reduced vessel densities of the superficial and deep vascular plexuses as compared to healthy controls. Higher choriocapillary vessel densities were associated with ongoing inflammatory disease activity during 24 months prior to OCT-A examination in MS and CIS patients.

CONCLUSION

Optic neuritis is associated with rarefaction of the superficial and deep retinal vessels. Alterations of the choriocapillaries might be linked to disease activity in MS.

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 retinal vascular network assessment in multiple sclerosis

Background:

Optical coherence tomography (OCT) angiography is a new method to assess the density of the vascular networks. Vascular abnormalities are considered involved in multiple sclerosis (MS) pathology.

Objective:

To assess the presence of vascular abnormalities in MS and to evaluate their correlation to disease features.

Methods:

A total of 50 MS patients with and without history of optic neuritis (ON) and 46 healthy subjects were included. All underwent spectral domain (SD)-OCT and OCT angiography. Clinical history, Expanded Disability Status Scale (EDSS), Multiple Sclerosis Severity Score (MSSS) and disease duration were collected.

Results:

Angio-OCT showed a vessel density reduction in eyes of MS patients when compared to controls. A statistically significant reduction in all SD-OCT and OCT angiography parameters was noticed both in eyes with and without ON when compared with control eyes. We found an inverse correlation between SD-OCT parameters and MSSS ( p = 0.003) and between vessel density parameters and EDSS ( p = 0.007).

Conclusion:

We report a vessel density reduction in retina of MS patients. We highlight the clinical correlation between vessel density and EDSS, suggesting that angio-OCT could be a good marker of disease and of disability in MS.

Optical coherence tomography angiography: Technical principles and clinical applications in ophthalmology

Optical coherence tomography angiography (OCTA) is a functional extension of OCT that provides information on retinal and choroidal circulations without the need for dye injections. With the recent development of high-speed OCT systems and efficient algorithms, OCTA has become clinically feasible. In this review article, we discuss the technical principles of OCTA, including image processing and artifacts, and its clinical applications in ophthalmology. We summarize recent studies which qualitatively or quantitatively assess disease presentation, progression, and/or response to treatment.

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.

Determination of Topographic Variations in Inner Retinal Blood Flow Areas in Young Chinese Subjects Using Optical Coherence Tomography Angiography

PURPOSE

To investigate (i) topographic variations in, and (ii) establish references for, inner retinal blood flow areas of the macular region of young Chinese subjects by means of optical coherence tomography (OCT) angiography.

METHODS

To measure inner retinal blood flow areas, we scanned an 8 × 8 mm² area and centered on the fovea of 336 eyes from 170 subjects using OCT angiography. Blood flow area measurements were made from a 1-mm radius circle, centered on the fovea, and 3 mm to the fovea superiorly, inferiorly, temporally, and nasally.

RESULTS

Mean inner retinal blood flow areas in the parafoveal, superior, inferior, nasal, and temporal macular regions were 1.78 ± 0.28, 1.76 ± 0.30, 1.69 ± 0.31, 1.91 ± 0.31, and 1.71 ± 0.28 mm,² respectively. Nasal inner retinal blood flow areas were significantly larger than other macular regions (p < 0.001). Gender was significantly associated with inner retinal blood flow areas of all macular regions studied. A gender-based subgroup analysis showed that inner retinal blood flow areas in superior, inferior, nasal, and temporal macular regions were significantly larger in women than men (all p < 0.05).

CONCLUSIONS

Nasal blood flow areas were larger than parafoveal blood flow areas, which were larger than superior blood flow areas, which were larger than temporal blood flow areas, which were larger than inferior blood flow areas in the macular regions studied. Gender was significantly associated with inner retinal blood flow areas in all macular regions studied.

Optical coherence tomography angiography enhances the detection of optic nerve damage in multiple sclerosis

BACKGROUND

Quantitative assessment of optic nerve damage is important in the evaluation of optic neuritis (ON) and multiple sclerosis (MS).

OBJECTIVE

To detect optic nerve damage using optical coherence tomography (OCT) and OCT angiography in MS.

METHODS

Peripapillary retinal nerve fibre layer (NFL) thickness, macular ganglion cell complex (GCC) thickness and Optic Nerve Head Flow Index (ONH-FI) were measured. The ONH-FI was defined as flow signal averaged over the optic disc. Diagnostic accuracy was evaluated by the area under the receiver-operating characteristics curve (AROC).

RESULTS

Sixty-eight eyes of 45 MS participants and 55 eyes of 32 healthy controls (HCs) were analysed. Of MS eyes, 25 had a history of ON (MS+ON) and 43 didn't (MS-ON). MS-ON and MS+ON eyes had reductions in ONH-FI (p=0.031 and p=0.001, respectively), GCC thickness (p=0.245 and p<0.001, respectively), and NFL thickness (p=0.003 and p=0.024, respectively), compared with HCs. The highest AROC (0.940) was achieved by the logistic regression combination of all three variables, which was significantly higher than other variables (p=0.018).

CONCLUSION

MS produces both retinal structural loss and decreased ONH perfusion in MS eyes with and without history of ON. The combination of perfusion and structural measurements enhances detection of optic nerve damage in MS. OCT angiography may be a useful additional retinal marker in evaluation of ON in MS.

Optical Coherence Tomography Angiography in Foveal Hypoplasia

BACKGROUND AND OBJECTIVE

A retrospective case series reporting optical coherence tomography angiography (OCTA) findings in foveal hypoplasia.

PATIENTS AND METHODS

Patients with foveal hypoplasia who presented to the authors' tertiary eye center. Cases of foveal hypoplasia that underwent OCTA were reviewed, and the clinical histories as well as imaging findings were summarized.

RESULTS

Three patients presented to the authors' eye center for evaluation of foveal hypoplasia and underwent OCTA: a 5-year-old girl, a 40-year-old woman, and a 22-year-old man. OCTA images were taken for both eyes of all patients. Four of five eyes with foveal hypoplasia had a small but present foveal avascular zone in the deep capillary plexus, whereas all eyes had an absent or severely reduced superficial capillary plexus.

CONCLUSION

OCTA can be helpful in the diagnosis of foveal hypoplasia and can aid in the anatomical characterization of disease. [Ophthalmic Surg Lasers Imaging Retina. 2016;47:1127-1131.].

Relationship Between Retinal Perfusion and Retinal Thickness in Healthy Subjects: An Optical Coherence Tomography Angiography Study

Purpose

To investigate the relationship between retinal perfusion and retinal thickness in the peripapillary and macular areas of healthy subjects.

Methods

Using spectral-domain optic coherence tomography and split-spectrum amplitude decorrelation angiography (SSADA) algorithm, retinal perfusion and retinal thicknesses in the macular and peripapillary areas were measured in healthy volunteers, and correlations among these variables were analyzed.

Results

Overall, 64 subjects (121 eyes) including 28 males and 36 females with a mean ± SD age of 38 ± 13 years participated. Linear mixed-models showed that vessel area density was significantly correlated with the inner retinal thickness (from the inner limiting membrane to the outer border of the inner nucleus layer; P < 0.05), but not with the thickness of the full retina (P > 0.05) in the parafoveal area. The area of the foveal capillary-free zone was negatively correlated with the inner and full foveal thicknesses (all P < 0.001). In the peripapillary area, the vessel area density was positively correlated with the thickness of the retinal nerve fiber layer (P < 0.001).

Conclusions

In healthy subjects, retinal perfusion in small vessels was closely correlated with the thickness of the inner retinal layers in both the macular and peripapillary areas.

Optical Coherence Tomography Angiography

Optical coherence tomography angiography (OCTA) is a noninvasive approach that can visualize blood vessels down to the capillary level. With the advent of high-speed OCT and efficient algorithms, practical OCTA of ocular circulation is now available to ophthalmologists. Clinical investigations that used OCTA have increased exponentially in the past few years. This review will cover the history of OCTA and survey its most important clinical applications. The salient problems in the interpretation and analysis of OCTA are described, and recent advances are highlighted.

Relationship between laser speckle flowgraphy and optical coherence tomography angiography measurements of ocular microcirculation

PURPOSE

The purpose of this study was to investigate the relationship between laser speckle flowgraphy (LSFG) and optical coherence tomography angiography (OCTA) measurements of ocular microcirculation in normal and open-angle glaucoma (OAG) subjects.

METHODS

This study included 18 eyes of 18 OAG patients and ten eyes of ten age-matched healthy controls. LSFG was used to measure mean blur rate (MBR) in the optic nerve head (ONH) vessel area (MV) and tissue area (MT). OCTA was used to measure a new parameter, peripapillary relative intensity (PRI), in the superficial retina, superficial choroid, and deep choroid. Statistical associations were then determined.

RESULTS

MV, MT, superficial-retinal PRI, and superficial-choroidal PRI were lower in the OAG subjects than the controls (P = 0.02, P < 0.001, P = 0.02 and P = 0.008, respectively). Superficial-retinal PRI was correlated with MV and MT (R = 0.68, P < 0.001 and R = 0.63, P < 0.001, respectively). Superficial-choroidal PRI was also correlated with MV and MT (R = 0.45, P = 0.02 and R = 0.57, P = 0.002, respectively). Multiple regression analysis revealed that MV and MT independently contributed to superficial-retinal PRI (P = 0.008 and P = 0.04, respectively), while only MT contributed to superficial-choroidal PRI (P = 0.03).

CONCLUSIONS

Our finding that OCTA-measured PRI was related to LSFG-measured MBR was reasonable, considering the vascular anatomy of the eye. Thus, PRI, like MBR, may be a promising biomarker of ocular microcirculation that can reveal the presence of ocular diseases such as OAG.

Study of the Radial Peripapillary Capillary Network in Congenital Optic Disc Anomalies With Optical Coherence Tomography Angiography

PURPOSE

To evaluate the radial peripapillary capillary network with optical coherence tomography angiography (angio-OCT) in morning glory syndrome (MGS), optic disc colobomas, and optic disc pits, and to explore possible correlations between the neural vascular structure and the pathogenesis of congenital optic disc anomalies.

DESIGN

Prospective observational comparative case series.

METHODS

Fifteen eyes of 15 patients with congenital optic disc anomalies were enrolled in this study. All patients underwent angio-OCT. The scans were centered on optic discs.

RESULTS

The mean age at presentation was 33 years (range: 19-50 years). Congenital optic disc anomalies were identified in all 15 eyes. Three eyes had the characteristic funduscopic signs of MGS, and angio-OCT scans of the peripapillary retina revealed a dense microvascular network. Optic disc colobomas were found in 5 eyes, and the characteristic funduscopic signs of optic pits were found in 7 eyes. Angio-OCT showed the absence of a radial peripapillary microvascular network in these 12 eyes.

CONCLUSION

The finding that angio-OCT scans confirmed the presence of a peripapillary microvascular network only in MGS cases supports the hypothesis that a primary neuroectodermal abnormality and a secondary mesenchymal abnormality leads to MGS. Angio-OCT is a safe, rapid imaging technique that could shed light on the pathogenesis of rare diseases of the optic disc.