Optical Coherence Tomography Angiography Characteristics of Iris Melanocytic Tumors

Assessment of conjunctival autograft reperfusion after pterygium surgery by optical coherence tomography angiography (OCT-A)

PURPOSE

To investigate the healing process of conjunctival autografts (CAG) following pterygium surgery using optical coherence tomography angiography (OCTA).

METHODS

Twenty-one eyes of 21 patients diagnosed with pterygium underwent pterygium excision with CAG without using Mitomycin-C. Over a 12-week follow-up period, changes in vascular density (VD), vascular density index (VDI), and vascular length density (VLD) were assessed at two distinct depths: superficial (<200 μm) and deep (>200 μm) using OCTA. Additionally, the revascularization rate and pattern were evaluated.

RESULTS

During the first week, the CAG was edematous and no sign of neovascularization was observed. In 4th week edema decreased and early signs of vascular formation appeared. In the 12th week, the deep vasculature demonstrated a greater density of interconnectivity compared to the superficial layers. VD and VLD significantly increased during the follow-up period (P < 0.05). The CAG blood flow signals exhibited a chaotic pattern, deviating from the expected centrifugal vascular pattern in the surrounding normal conjunctiva.

CONCLUSION

OCTA imaging emerges as a reliable tool for the assessment of CAG vascularization, improving the monitoring of the healing process in the postoperative period. The evaluation of CAG revascularization patterns appears to be promising biomarkers that can predict the potential future recurrence.

Cysts and tumours of the iris: Diagnostic tools and key management considerations-A review

The iris is a unique structure, with exquisite variations in colour and form. Pathological changes, specifically including iris cysts and tumours are relatively uncommon, difficult to diagnose, and yet potentially blinding or life-threatening. Based on a comprehensive literature review, with highly illustrated key case examples, this report aims to guide the clinician in filtering the differential diagnoses of iris cysts and tumours. Evaluation is in the context of key diagnostic clinical tools and management considerations. Diagnostic imaging techniques include serial anterior segment photography, ultrasound, anterior segment optical coherence tomography, and iris fluorescein angiography, however, the roles of computerised topography and magnetic resonance imaging are also considered in this review. Management includes categorisation in terms of solid iris tumours (melanocytic vs. non-melanocytic), or iris cysts (primary vs. secondary) that may be usefully differentiated by clinical assessment, avoiding more invasive interventions. Cystic lesions are generally benign, although implantation cysts in particular cause significant complications and surgical challenges. Most solid tumours are melanocytic and also typically benign. However, in larger lesions, rapid growth, symptoms and complications more likely indicate malignancy, requiring further investigation.

The use of optical coherence tomography angiography to measure changes in iris vasculature after strabismus surgery

INTRODUCTION

Anterior segment ischemia (ASI) is a rare but potentially sight-threatening complication of strabismus surgery. Preoperative imaging of the iris vasculature may be appropriate in patients at high risk of ASI. In clinical practice, this is currently done through invasive fluoresceine or indocyanine green (ICG) angiography and in study context through laser speckle contrast imaging. The purpose of this study is to investigate the use of noninvasive optical coherence tomography angiography (OCTA) as a screening tool for ASI in strabismus surgery.

METHODS

A prospective interventional trial was conducted from September until November 2021 at the Leuven University Hospitals. Patients scheduled for strabismus surgery to one or more rectus muscles underwent OCTA preoperatively and at day two postoperatively. The vascular density was calculated for all images with sufficient quality. Information on risk factors for ASI was collected. A two-sided t-test was used for pairwise comparison pre- and postoperatively. Filling defects were qualitatively assessed.

RESULTS

Eighteen patients were included. In only seven muscles of five patients, images of sufficient quality on both image acquisition moments were suitable for statistical analysis. The mean age of these patients was 45.2 years and 40% were women. A mean vascular density of 53,099% preoperatively and a mean density of 50,782% postoperatively with a mean decrease of 2.316% (p = .318, 95% confidence interval [-2.886; 7.516]) was found. No filling defects were identified.

DISCUSSION

The small final number of images contributing to statistical analysis shows that current application of the OCTA technique is hampered by poor image quality and poor repeatability. We identified difficulties in the image acquisition process and variable pupil size due to iris muscle contractions as the two main reasons. We believe that adjustments in the OCTA software such as pupil tracking and tracking of iris vasculature can largely overcome these limitations. Furthermore, there is a need for a normative database to allow good quantitative comparison and risk stratification. We conclude that OCTA could be suitable for screening in prevention of ASI with both qualitative and quantitative analysis if adjustments are made.

Current clinical applications of anterior segment optical coherence tomography angiography: a review

Optical coherence tomography (OCT) is a revolutionary in vivo imaging technology that presents real-time information on ocular structures. Angiography based on OCT, known as optical coherence tomography angiography (OCTA), is a noninvasive and time-saving technique originally utilized for visualizing retinal vasculature. As devices and built-in systems have evolved, high-resolution images with depth-resolved analysis have assisted ophthalmologists in accurately localizing pathology and monitoring disease progression. With the aforementioned advantages, application of OCTA has extended from the posterior to anterior segment. This nascent adaptation showed good delineation of the vasculature in the cornea, conjunctiva, sclera, and iris. Thus, neovascularization of the avascular cornea and hyperemia or ischemic changes involving the conjunctiva, sclera, and iris has become prospective applications for AS-OCTA. Although traditional dye-based angiography is regarded as the gold standard in demonstrating vasculature in the anterior segment, AS-OCTA is expected to be a comparable but more patient-friendly alternative. In its initial stage, AS-OCTA has exhibited great potential in pathology diagnosis, therapeutic evaluation, presurgical planning, and prognosis assessments in anterior segment disorders. In this review of AS-OCTA, we aim to summarize scanning protocols, relevant parameters, and clinical applications as well as limitations and future directions. We are sanguine about its wide application in the future with the development of technology and refinement in built-in systems.

Angiographic Features of Iris Melanocytic Tumors: Nevus versus Melanoma

Introduction

Determining the nature of iris melanocytic tumors based on clinical exam alone remains challenging. Tumor-associated vasculature of iris melanocytic lesions may facilitate the ability to discern between iris nevus and melanoma.

Methods

In a single-institution, retrospective, observational study of 45 patients with pathologically confirmed iris melanoma and 15 patients with iris nevi that were either clinically stable or pathologically confirmed were included. Tumor characteristics and associated vasculature were identified on clinical exam and slit-lamp photographs. Fluorescein angiographic parameters including feeder vessels, intrinsic vessels, leakage, masking, and angiographic silence were assessed.

Results

Feeder vessels were present in 17 (43%) melanomas and were absent in the nevus group (p = 0.002). Thirty-three (83%) iris melanomas and 5 (33%) iris nevi were observed to have intrinsic vessels, and a statistically significant association of intrinsic vessels with malignancy (p = 0.001) was noted. Fluorescein leakage was also observed more frequently in iris melanoma 39 (98%) than in nevi 9 (60) with a significant difference (p = 0.001). Angiographic silence occurred in 3 nevi (20%) and was not observed in any melanoma (p = 0.017). Overall, the presence of intrinsic vessels +/- feeder vessels had high sensitivity (0.85) and high positive predictive value (0.87) for diagnosis of iris melanoma.

Conclusions

Anterior segment fluorescein angiography allows for the assessment of tumor-associated vascular patterns and demonstrates utility in differentiating iris nevi from melanoma. Feeder vessels were only observed in iris melanoma and were absent in iris nevi. The intrinsic vessels were present more frequently in melanomas and are thus associated with malignancy. Angiographic silence is indicative of iris nevi.

In vivo ocular microvasculature imaging in rabbits with 3D ultrasound localization microscopy

Morphological and hemodynamic changes in the ocular vasculature are important signs of various ocular diseases. The evaluation of the ocular microvasculature with high resolution is valuable in comprehensive diagnoses. However, it is difficult for current optical imaging techniques to visualize the posterior segment and retrobulbar microvasculature due to the limited penetration depth of light, particularly when the refractive medium is opaque. Thus, we have developed a 3D ultrasound localization microscopy (ULM) imaging method to visualize the ocular microvasculature in rabbits with micron-scale resolution. We used a 32 × 32 matrix array transducer (center frequency: 8 MHz) with a compounding plane wave sequence and microbubbles. Block-wise singular value decomposition spatiotemporal clutter filtering and block-matching 3D denoising were implemented to extract the flowing microbubble signals at different imaging depths with high signal-to-noise ratios. The center points of microbubbles were localized and tracked in 3D space to achieve the micro-angiography. The in vivo results demonstrate the ability of 3D ULM to visualize the microvasculature of the eye in rabbits, where vessels down to 54 μm were successfully revealed. Moreover, the microvascular maps indicated the morphological abnormalities in the eye with retinal detachment. This efficient modality shows potential for use in the diagnosis of ocular diseases.

Advances in swept-source optical coherence tomography and optical coherence tomography angiography

Background

The fast development of swept-source optical coherence tomography (SS-OCT) and swept-source optical coherence tomography angiography (SS-OCTA) enables both anterior and posterior imaging of the eye. These techniques have evolved from a research tool to an essential clinical imaging modality.

Main text

The longer wavelength and faster speed of SS-OCT and SS-OCTA facilitate better visualization of structure and vasculature below pigmented tissue with a larger field of view of the posterior segment and 360-degree visualization of the anterior segment. In the past 10 years, algorithms dealing with OCT and OCTA data also vastly improved the image quality and enabled the automated quantification of OCT- and OCTA-derived metrics. This technology has enriched our current understanding of healthy and diseased eyes. Even though the high cost of the systems currently limited the widespread use of SS-OCT and SS-OCTA at the first beginning, the gap between research and clinic practice got obviously shortened in the past few years.

Conclusions

SS-OCT and SS-OCTA will continue to evolve rapidly, contributing to a paradigm shift toward more widespread adoption of new imaging technology in clinical practice.

A two-stage framework for optical coherence tomography angiography image quality improvement

Introduction

Optical Coherence Tomography Angiography (OCTA) is a new non-invasive imaging modality that gains increasing popularity for the observation of the microvasculatures in the retina and the conjunctiva, assisting clinical diagnosis and treatment planning. However, poor imaging quality, such as stripe artifacts and low contrast, is common in the acquired OCTA and in particular Anterior Segment OCTA (AS-OCTA) due to eye microtremor and poor illumination conditions. These issues lead to incomplete vasculature maps that in turn makes it hard to make accurate interpretation and subsequent diagnosis.

Methods

In this work, we propose a two-stage framework that comprises a de-striping stage and a re-enhancing stage, with aims to remove stripe noise and to enhance blood vessel structure from the background. We introduce a new de-striping objective function in a Stripe Removal Net (SR-Net) to suppress the stripe noise in the original image. The vasculatures in acquired AS-OCTA images usually exhibit poor contrast, so we use a Perceptual Structure Generative Adversarial Network (PS-GAN) to enhance the de-striped AS-OCTA image in the re-enhancing stage, which combined cyclic perceptual loss with structure loss to achieve further image quality improvement.

Results and discussion

To evaluate the effectiveness of the proposed method, we apply the proposed framework to two synthetic OCTA datasets and a real AS-OCTA dataset. Our results show that the proposed framework yields a promising enhancement performance, which enables both conventional and deep learning-based vessel segmentation methods to produce improved results after enhancement of both retina and AS-OCTA modalities.

Iris Racemose Hemangioma Assessment with Swept Source Optical Coherence Tomography Angiography: A Feasibility Study and Stand-Alone Comparison

Purpose: To evaluate arteriovenous malformations (AVM) with swept-source (SS) optical coherence tomography (OCT) angiography (OCTA) in iris racemose hemangioma and compare it with traditional intravenous iris fluorescein angiography (IVFA). Methods: A cross-sectional observational clinical study was conducted on patients with iris racemose hemangioma with the ZEISS PLEX Elite 9000 SS OCT & OCTA. Results: Three eyes of three patients were imaged. Iris racemose hemangiomas demonstrated a tortuous, well-defined, and continuous course of the AVM. The ZEISS PLEX Elite 9000 SS OCT & OCTA allowed for a detailed visualization of the ARM and was superior to IVFA in depicting small caliber, fine vessels. Conclusions: SS-OCTA may provide a dye-free, no-injection, cost-effective method comparable to spectral domain OCTA and IVFA for diagnosing and monitoring iris racemose hemangiomas for growth and vascularity.

Endoscopic OCT Angiography Using Clinical Proximal-End Scanning Catheters

Endoscopic optical coherence tomography angiography (OCTA) is a promising modality to inspect the microvasculature of inner organs in the early-stage tumor diagnosis. However, an endoscopic clinical proximal-end scanning catheter has limited flow imaging capability due to the nonuniform rotational distortion (NURD) and physiological motion. In this study, a combined local and global (CLG) optical flow algorithm was used to estimate the motion vectors caused by NURD and physiological motion. The motion vectors were used to bicubic-interpolation-resample the OCT structure to ensure that the circumferential pixels were equally spaced in the space domain. Then, angiograms were computed based on the statistical relation between inverse SNR (iSNR) and amplitude decorrelation (IDa), termed as IDa-OCTA. Finally, the ability of this technique for endoscopic OCTA imaging was demonstrated by flow phantom experiments and human nailfold capillary imaging.

Imaging of iris vasculature: current limitations and future perspective

Fluorescein and indocyanine green angiography have been the traditional ways to image the vasculature of the iris in the last few decades. Because of the invasive nature of these procedures, they are performed in rare situations, and thus, our understanding about iris vasculature is very limited. Optical coherence tomography angiography (OCTA) is a noninvasive imaging method that enables the detailed visualization of the retinal and choroidal vascular networks. More recently, it has been also used for the examination of the iris vasculature in healthy and disease eyes. However, there is a lack of uniformity in the image acquisition protocols and interpretations in both healthy and pathological conditions. Artifacts of iris OCTA include shadowing, motion, segmentations errors, mirror effects. OCTA devices have an eye-tracking system designed for the posterior segment and the applications of these systems on the anterior segment can determine motion lines, vessel duplication, and vessel discontinuity. OCTA of the iris should always be performed under ambient room lighting to create miosis and reduce iris vasculature changes during the examination. In the near future, eye-tracking systems specifically designed for the iris vessels could permit the follow-up function, and the development of new OCTA metrics could reveal interesting applications of this new imaging technique.

High speed, long range, deep penetration swept source OCT for structural and angiographic imaging of the anterior eye

This study reports the development of prototype swept-source optical coherence tomography (SS-OCT) technology for imaging the anterior eye. Advances in vertical-cavity surface-emitting laser (VCSEL) light sources, signal processing, optics and mechanical designs, enable a unique combination of high speed, long range, and deep penetration that addresses the challenges of anterior eye imaging. We demonstrate SS-OCT with a 325 kHz A-scan rate, 12.2 µm axial resolution (in air), and 15.5 mm depth range (in air) at 1310 nm wavelength. The ultrahigh 325 kHz A-scan rate not only facilitates biometry measurements by minimizing acquisition time and thus reducing motion, but also enables volumetric OCT for comprehensive structural analysis and OCT angiography (OCTA) for visualizing vasculature. The 15.5 mm (~ 11.6 mm in tissue) depth range spans all optical surfaces from the anterior cornea to the posterior lens capsule. The 1310 nm wavelength range enables structural OCT and OCTA deep in the sclera and through the iris. Achieving high speed and long range requires linearizing the VCSEL wavenumber sweep to efficiently utilize analog-to-digital conversion bandwidth. Dual channel recording of the OCT and calibration interferometer fringe signals, as well as sweep to sweep wavenumber compensation, is used to achieve invariant 12.2 µm (~ 9.1 µm in tissue) axial resolution and optimum point spread function throughout the depth range. Dynamic focusing using a tunable liquid lens extends the effective depth of field while preserving the lateral resolution. Improved optical and mechanical design, including parallax “split view” iris cameras and stable, ergonomic patient interface, facilitates accurate instrument positioning, reduces patient motion, and leads to improved imaging data yield and measurement accuracy. We present structural and angiographic OCT images of the anterior eye, demonstrating the unique imaging capabilities using representative scanning protocols which may be relevant to future research and clinical applications.

[Use of optical coherence tomography angiography in assessment in conjunctival vascular architecture in health and pathology]

PURPOSE

Investigation of the capabilities of anterior segment (AS) optical coherence tomography angiography (OCTA) in evaluation of conjunctival vascular architecture in healthy individuals and in various pathological conditions.

MATERIAL AND METHODS

The study included 17 healthy volunteers (34 eyes; the control group) and 62 patients (68 eyes) with conjunctival lesions of various nature. All participants underwent AS-OCT and AS-OCTA with assessment of qualitative (vessels pattern, lumen, pathologic tortuosity) and quantitative parameters (vessel density (VD, %) in the lesion area). Mean VD (MVD) and local VD (LVD) were determined, as well as VD in perifocal tissues (PVD).

RESULTS

OCTA scans in 8 conjunctival sectors showed mostly radial pattern of the vascular architecture, with vessel lumen remaining the same over their entire visible length. Larger-sized vessels in deeper conjunctival layers were discovered in most cases. The lowest VD value (33.3%) was registered in the superotemporal quadrant, and the highest (38.9%) - in the nasal. Tortuosity of the vessels with course disruption, uneven lumen over the length of the vessels and increase in VD were observed in the area of conjunctival lesions in all cases excluding congenital abnormalities, pingueculae and conjunctival melanocytic intraepithelial neoplasia. The malignant nature of the tumors was indicated by dense vessel distribution and difficulties for visualization of intravascular space, and confirmed by pathohistological analysis. An increase in the number of areas with a lace-like pattern was characteristic for melanomas, with mean VD of more than 50% in the most vascularized areas.

CONCLUSION

AS-OCTA is an informative method for the visualization of vessels in healthy conjunctiva and in conjunctival pathology. Local VD in the lesion area should be measured when the vessels are unevenly distributed.

Appearance of Tumor Vessels in Patients With Choroidal Osteoma Using Swept-Source Optical Coherence Tomographic Angiography

Objective

To report the morphologic characteristics of tumor-related vasculatures and their association with secondary choroidal neovascularization (CNV), subretinal fluid (SRF), choroidal thickness, retinal pigment epithelium (RPE) alterations, subretinal hemorrhage, and tumor decalcification in eyes with choroidal osteoma (CO), using swept-source optical coherence tomographic angiography (SS-OCTA).

Design

Cross-sectional observational study.

Participants

We included 26 patients recruited from Beijing Tongren Hospital with a diagnosis of CO, based on the presence of yellow-orange mass deep to the RPE under indirect ophthalmoscopy and occupying the choroid with well-defined margins and bone density on ultrasonography or computed tomography and focal hyperfluorescent spots with no homogeneous pattern on fluorescein angiography/indocyanine green angiography (FA/ICGA). Data were collected from April 1, 2020, to April 1, 2021, and analyzed from April 30 through May 30, 2021.

Methods

Applying SS-OCTA systems operating at 1,050-nm wavelengths, eyes with CO were imaged.

Main Outcome and Measures

Tumor-related vasculature in eyes with CO was characterized using multimodal imaging that included fundus photography, FA/ICGA, SS-OCT, and SS-OCTA, and the images were anatomically aligned. CO thickness was manually measured as the distance between the upper boundary of the tumor and the underlying sclerochoroidal interface on the SS-OCT images. Subfoveal choroidal thickness was manually measured as the distance between the Bruch membrane and the sclerochoroidal interface on the SS-OCT images.

Results

Of the 26 Asian patients, 16 (62%) were women and 10 (38%) were men. The mean age was 26.8 years (median, 23; range, 8–45 years), and the mean best corrected visual acuity (BCVA) was 20/40. Thirty-three eyes underwent imaging and were diagnosed with CO. Indocyanine green angiography identified inhomogeneous hyperfluorescence due to tumor-related vasculature, and all corresponded to the structures that appeared as sea-fan vascular networks (SFVNs) combined with clusters of tangled vessels on SS-OCTA images. SFVNs were detected on SS-OCTA imaging in all eyes (100%), terminal tangled vascular structures in 32 of 33 eyes (97%), but not identified on ICGA. Of the 33 tangled vascular structures, 32 (97%) were located at the edge of or inside the tumor, and only 1 (3%) was associated with type 2 neovascularization. In addition, SS-OCT revealed SRF in 33 eyes (100%), 33 (100%) were located at the edge of CO, and only 1 was underlying macular. SRF with retinal edema was seen in 30 of 32 eyes (94%).

Conclusions

In eyes with CO undergoing SS-OCTA imaging, tumor-related vasculature appears as SFVNs combined with tangled vascular structures or few type 2 neovascularization. The identification of actual tumor vasculature in patients with CO as SFVNs with inner or terminal vascular tangles rather than previously described CNV may help facilitate understanding of their pathogenesis, tumor control, and response to treatment.

Changes in Limbal Optical Coherence Tomography Angiography Outcomes in Patients With Overnight Contact Lens Wear

OBJECTIVES

To evaluate the perilimbal vasculature of patients who wear contact lenses (CLs) overnight with optical coherence tomography angiography (OCTA) and compare the results with healthy population.

METHODS

Forty-two patients were included in this observational study. The OCTA imaging was performed in the temporal quadrant of the perilimbal region using a swept-source optical coherence tomography system (Triton DRI-OCT; Topcon Corporation, Tokyo, Japan). The assessments were made in two depths: starting from the conjunctival epithelium to 200 μm scleral depth and the scleral depth between 200 and 1,000 μm. The vessel density, vessel length density, vessel diameter index, and fractal dimension were the main outcomes and compared between overnight CL users and healthy population.

RESULTS

Twenty-two patients who have been using CLs overnight for at least 3 months and 20 healthy individuals were included in the study. The vessel density at the superficial layer was significantly higher in the CL group compared with the control group (P<0.001). Vessel diameter index, vessel length density, and fractal dimension at the superficial layer did not differ between the groups (P>0.05 for all). There was no difference in the vessel density, vessel diameter index, vessel length density, and fractal dimension in the deep layer between the groups (P>0.05 for all).

CONCLUSIONS

Patients who use CL overnight exhibit increased vessel density in the superficial layers of the perilimbal region, which may suggest new vessel formation in the conjunctiva. Anterior segment OCTA may be useful to evaluate the initial changes in limbal vasculature in CL users.

Iris Cysts: Clinical Features, Imaging Findings, and Treatment Results

Objectives:

To report the clinical and demographic characteristics, imaging findings, treatment results, and follow-up data of patients with iris cysts.

Materials and Methods:

The medical records of 37 patients with iris cysts were retrospectively analyzed. Ultrasound biomicroscopy (UBM), swept-source optical coherence tomography (SS-OCT), and SS-OCT angiography (SS-OCTA) were performed to examine the iris cysts.

Results:

The mean age of the patients was 34.4 years, ranging from 5 to 85 years. Twenty-four patients (65%) were female and 13 (35%) were male. Mean follow-up period was 21.3 months, ranging from 4 months to 8 years. Thirty-five (94.5%) of the cysts were classified as primary and 2 (4.5%) were classified as secondary. Thirty-one (83.7%) of the primary cysts were pigment epithelial and 4 were stromal. Primary iris pigment epithelial cysts were classified as peripheral in 26 patients (72.2%), midzonal in 4 (11.1%), and dislodged in 1 (2.7%). Stromal cysts were classified as acquired in 3 patients (8.1%) and congenital in 1 patient (2.7%). Secondary iris cysts were caused by perforating eye injury. UBM could visualize both the anterior and posterior surfaces of the cysts (26 patients). Anterior segment SSOCT could visualize the anterior but not the posterior surface of the cysts (4 patients). Iris cysts did not display intrinsic vascularity on SS-OCTA (4 patients). All pigment epithelial cysts were managed by observation. Of the 4 primary stromal cysts, 3 were managed by surgical excision and 1 by observation. Two secondary cysts required surgical removal.

Conclusion:

Pigment epithelial cysts generally remain stable without need for treatment. However, iris stromal cysts frequently require surgical intervention. UBM and SS-OCT were valuable in the diagnosis of iris cysts. On UBM, iris cysts appear with a thin, hyperechoic wall with hypoechoic internal content. Iris cysts did not have intrinsic vascularity on anterior segment SS-OCTA.

Optical coherence tomography angiography application to pigmented iris: Could a new index quantify blood flow?

PURPOSE

To assess the blood flow and vascular visibility of irises in relation to pigmentation and pupil size, using an anterior segment optical coherence tomography angiography (OCTA).

MATERIALS AND METHODS

This is a cross-sectional study. OCTA images were acquired in the nasal and temporal quadrants from a cohort of 30 healthy subjects in photopic (miosis) and scotopic (mydriasis) conditions. Patients were divided according to iris color (less pigmented: group L vs more pigmented: group D). Vascular parameters (vessel density (VD), vessel length density (VLD), fractal dimension (FD)) were applied and compared among groups L and D, location and different pupil status. A novel vascular index called Luminance Index (LI) was developed and applied in order to quantify vascular flow and evaluate its variation in photopic and scotopic conditions. Multivariable analyses were performed to evaluate possible predictors of VD and LI.

RESULTS

No differences were found for all vascular measurements (VD, VDL, FD, LI) between nasal and temporal quadrants. All vascular measurements were higher in group L than in group D (p < 0.05), except for LI and FD in photopic condition. In group L, all vascular parameters increased (p < 0.001) after dark adaptation. In group D, only LI increased after dark adaptation (p < 0.001). Pigmentation and iris thickness were significantly associated with VD in scotopic and photopic conditions, and with LI only in scotopic condition.

CONCLUSIONS

Pigmentation still remains a major issue for vascular visibility. Quantitative and qualitative vascular changes follow pupil size variation. LI could be a new surrogate to quantify blood flow.

Longitudinal Assessment of Alkali Injury on Mouse Cornea Using Anterior Segment Optical Coherence Tomography

Purpose

Chemical burns due to alkalis cause extensive damage to the ocular surface leading to blindness. Assessment of ocular burn could be challenging due to severe opacity, inflammation, and angiogenesis. Anterior segment optical coherence tomography (AS-OCT) and OCT angiography (OCTA) may provide fast, non-invasive deep tissue visualization of pathology with high sensitivity in conjunction with slit-lamp analysis.

Methods

C57-BL/6J mice were anesthetized with ketamine/dexmedetomidine, and corneal alkali burn was induced (n = 6) by placing filter paper soaked in 1-M sodium hydroxide for 30 seconds on the right eye while the left eye was kept as control. Longitudinal imaging was done with AS-OCT/OCTA and fluorescein angiography at various time intervals for 14 days.

Results

AS-OCT showed characteristic pathological changes in alkali-burned eyes with high sensitivity. Although OCT/OCTA showed three-dimensional and cross-sectional views of the anterior chamber and angiogenesis, fluorescein angiography showed nascent vessels with active leakage. Corneal swelling progressively increased by 125.26% on day 12 with a high prevalence of epithelial bullae, stromal cysts, stromal splitting, and Descemet's membrane detachment. Neovascularization was noted as early as day 4 in the burned eyes by both methods. Severe corneal opacity and anterior chamber inflammation were also detected by AS-OCT/OCTA.

Conclusions

AS-OCT/OCTA is a promising, noninvasive, high-resolution imaging modality that can provide both qualitative and quantitative information regarding deep tissue pathology at a structural level.

Translational Relevance

Noninvasive AS-OCT/OCTA and fluorescein methods show promise in clinical pathology evaluation for ocular injury management and prognostic indications, as the early presence of Descemet's membrane detachment and corneal swelling appears to be correlated with the severity and localization of corneal neovascularization.

[Optical coherence tomography angiography (OCT-A) : Overview of the technique and the possible clinical and scientific applications]

Optical coherence tomography angiography (OCT-A) is a very promising noninvasive imaging modality. For the first time it enables a precise 3‑dimensional depiction of the retinal microcirculation without the use of contrast medium and can be carried out rapidly and simply. This makes OCT‑A interesting for both scientific and clinical applications. In many ophthalmological diseases, such as glaucoma and diabetic retinopathy, OCT‑A can detect vascular alterations even in the early stages of the disease. These alterations partially correlate with functional parameters. The use of OCT‑A in the clinical routine is currently still limited due to imaging artifacts, high acquisition costs and large amounts of data; however, the scientific interest in this new technology is enormous and from our point of view it will become established in the clinical routine in the future.

Application of Corneal Optical Coherence Tomography Angiography for Assessment of Vessel Depth in Corneal Neovascularization

PURPOSE

To map and measure the depths of corneal neovascularization (NV) using 3-dimensional optical coherence tomography angiography (OCTA) at 2 different wavelengths.

METHODS

Corneal NV of varying severity, distribution, and underlying etiology was examined. Average NV depth and vessel density were measured using 840-nm spectral-domain OCTA and 1050-nm swept-source OCTA. The OCTA results were compared with clinical slit-lamp estimation of NV depth.

RESULTS

Twelve eyes with corneal NV from 12 patients were imaged with OCTA. Clinically "superficial," "midstromal," and "deep" cases had an average vessel depth of 23%, 39%, and 66% on 1050-nm OCTA, respectively. Average vessel depth on OCTA followed a statistically significant ordinal trend according to the clinical classification of vessel depth (Jonckheere-Terpstra test, P < 0.001). In 8 cases where both 840-nm OCTA and 1050-nm OCTA were acquired, there was excellent agreement in the mean vessel depth between the 2 systems (concordance correlation coefficient = 0.94, P < 0.001). The average vessel density measured by 840-nm OCTA was higher (average 1.6-fold) than that measured by 1050-nm OCTA.

CONCLUSIONS

Corneal OCTA was able to map corneal NV in 3 dimensions and measure vessel depth and density. The depth of corneal NV varied between different pathologies in a manner consistent with previous pathologic studies. The measured vessel density appeared to be affected by the interscan time, which affects blood flow velocity sensitivity, and the wavelength, which affects the ability to penetrate through opacity. These findings suggest possible clinical applications of OCTA for the diagnosis of corneal pathology and quantitative monitoring of therapeutic response in patients with corneal NV.

Anterior Segment OCTA of Melanocytic Lesions of the Conjunctiva and Iris

PURPOSE

To study the feasibility and diagnostic value of vascular imaging using optical coherence tomography (OCT)-angiography (OCTA) of melanocytic lesions of the conjunctiva and iris.

DESIGN

Cross-sectional study.

METHODS

Twenty-five patients with an untreated conjunctival lesion (5 melanoma, 13 nevus, 7 primary acquired melanosis [PAM]) and 52 patients with an untreated iris lesion (10 melanoma, 42 nevus) were included. Patients were imaged using a commercially available OCTA device, with the addition of an anterior segment lens and manual focussing. Tumor vessel presence, vascular patterns and vascular density were assessed.

RESULTS

Good OCTA images were obtained in 18 of 25 conjunctival lesions and 42 of 52 iris lesions. Failure was caused by lack of patient cooperation, an unfavorable location, or mydriasis. In all imaged conjunctival lesions and 77% of iris lesions, vascular structures were detected. Conjunctival melanoma and nevi demonstrated the same intralesional tortuous patterns, whereas vasculature in eyes with PAM was similar to normal conjunctiva. Both iris melanoma and nevi demonstrated tortuous patterns, distinct from the radially oriented normal iris vasculature.

CONCLUSIONS

Optical coherence tomography angiography (OCTA) allows for noninvasive imaging of the vasculature in melanocytic lesions of the conjunctiva and iris. Good image quality depends highly on patient cooperation and lesion characteristics. Differentiation of benign and malignant lesions was not possible. New software is called for to improve image acquisition and analysis.

Multimodal Imaging of Microvascular Abnormalities in Retinal Vein Occlusion

The technologies of ocular imaging modalities such as optical coherence tomography (OCT) and OCT angiography (OCTA) have progressed remarkably. Of these in vivo imaging modalities, recently advanced OCT technology provides high-resolution images, e.g., histologic imaging, enabling anatomical analysis of each retinal layer, including the photoreceptor layers. Recently developed OCTA also visualizes the vascular networks three-dimensionally, which provides better understanding of the retinal deep capillary layer. In addition, ex vivo analysis using autologous aqueous or vitreous humor shows that inflammatory cytokine levels including vascular endothelial growth factor (VEGF) are elevated and correlated with the severity of macular edema (ME) in eyes with retinal vein occlusion (RVO). Furthermore, a combination of multiple modalities enables deeper understanding of the pathology. Regarding therapy, intravitreal injection of anti-VEGF drugs provides rapid resolution of ME and much better visual improvements than conventional treatments in eyes with RVO. Thus, the technologies of examination and treatment for managing eyes with RVO have progressed rapidly. In this paper, we review the multimodal imaging and therapeutic strategies for eyes with RVO with the hope that it provides better understanding of the pathology and leads to the development of new therapies.

Dynamic optical coherence tomography shows characteristic alterations of blood vessels in malignant melanoma

BACKGROUND

Dynamic optical coherence tomography (D-OCT) allows in vivo visualization of blood vessels in the skin and in malignant tumours. Vessel patterns in malignant melanoma may be associated with tumour stage.

OBJECTIVE

The aim of this study was to describe blood vessel patterns in melanomas and to correlate them with stage.

METHODS

One hundred fifty-nine malignant melanomas were assessed in a multicentre study. Every tumour was imaged using D-OCT prior to surgery and histologic evaluation. The tumour data such as thickness and ulceration as well as the staging at primary diagnosis and a follow-up of at least 40 months resulted in a stage classification. The vessel patterns were assessed according to predefined categories, compared with healthy adjacent skin, and correlated to stage.

RESULTS

Melanomas contained more blood vessels in different patterns compared with healthy adjacent skin. In particular, irregular vascular shapes such as blobs, coils, curves and serpiginous vessels were more common in melanomas. In addition, these patterns were significantly more often found in high-risk and metastatic melanomas than in low-risk lesions.

CONCLUSION

In melanomas, the density of the blood vessels is increased, and irregular vascular patterns are more frequent. At higher stages, especially in metastatic melanomas, these atypical vessels are significantly more common.

Optical coherence tomography angiography characteristics of choroidal melanoma

PURPOSE

The purpose of this study is to evaluate tumour vasculature with optical coherence tomography angiography (OCTA) in malignant choroidal melanoma (CM).

MATERIALS AND METHODS

Patients with unilateral CM were included in this cross-sectional observational clinical study. Applying OCTA systems operating at 840-nm wavelengths, eyes with CM were imaged. The primary main outcome measures were OCTA images, qualitative evaluation of macular and tumour vasculature, quantitative vascular density (VD), perfusion density (PD) and the foveal avascular zone disruption.

RESULTS

The study included 11 patients with unilateral CM and contralateral unaffected eyes as the control group. Eyes of 11 patients with CM and contralateral unaffected eyes were imaged before brachytherapy and 5 patients were imaged post brachytherapy. CM is demonstrated dense, tortuous blood vessels, uneven thickness and relatively disorganised intratumoural vasculature. In 11 eyes with CM, the VD and PD in the macular area were significantly lower within affected eyes (131.333 ± 27.807%, 3.152 ± 0.714%, p < 0.0001) than in contralateral eyes (154.208 ± 5.599%, 3.662 ± 0.127%, p < 0.0001). The VD and PD in the tumour area (67.990 ± 34.899%, 1.617 ± 0.847%, p < 0.0001) were significantly lower when compared to the macular area of affected eyes (131.333 ± 27.807%, 3.152 ± 0.714%, p < 0.0001) and the macular area of contralateral eyes (154.208 ± 5.599%, 3.662 ± 0.127%, p < 0.0001). After radiation treatment, the VD and PD in five CM eyes (116.526 ± 7.598%, 2.438 ± 0.358%, p < 0.05) were significantly lower than before treatment (141.544 ± 14.645%, 3.327 ± 0.354%, p < 0.05). Tumour regression after radiation therapy for melanomas was associated with decreased vessel density.

CONCLUSIONS

OCTA can provide a dye-free, non-invasive, reliable method to monitor a variety of tumours, including CM for growth and vascularity. Upon OCTA, this could be helpful in evaluating the variety of tumour blood vessels before and after brachytherapy to judge the curative effect and whether the tumour recurred. Detection of the characteristic vascular features of CM by OCTA could make OCTA an assuring diagnostic modality to differentiate malignant lesions.

Optical coherence tomography angiography characteristics of optic disc melanocytoma

Background

Optic disc melanocytoma (ODMC) was a benign pigmented intraocular tumor with the rare potential malignant transformation. This study was designed to evaluate tumor vasculature with optical coherence tomography angiography (OCTA) in ODMC.

Methods

Eyes of healthy individuals in a control group and of patients with ODMC were imaged by OCTA systems operating at 840 nm wavelengths and examined. The main outcome measures were OCTA images, qualitative evaluation of optic disc and tumor vasculature, quantitative vascular density (VD) and perfusion density (PD).

Results

One eye of ten normal volunteers and ten patients with ODMC were imaged. Eyes affected by ODMC as compared to the eyes of the control group (all P < 0.05). The healthy optic disc had radially-oriented vessels within the retina on OCTA. Optic disc melanocytoma was characterized by globular, demonstrated tortuous blood vessels, uneven thickness, and relatively disorganized intratumoral vasculature. The VD and PD within ODMC were significantly higher (12.360% ± 4.175, 0.316% ± 0.119%, P < 0.0001) than in normal optic discs (4.160% ± 2.290, 0.102% ± 0.0, 56%, P < 0.0001). No significant differences were established of the VD and PD in each single measurement zone (P > 0.05) between the ODMC and the control eyes. At 840 nm, OCTA could provide sufficient visualization of the tumor vasculature and better penetration through thicker tumors. The full thickness was visualized even in thicker tumors and highly pigmented lesions (> 2 mm). Interpretable OCTA images were obtained in 96% of the participants in whom imaging was attempted.

Conclusions

OCTA may provide a noninvasive, safe, and efficient technique for evaluating a variety of neoplasms including the growth and vascularity in ODMC. OCTA could facilitate the evaluation of the vascular abnormalities of tumors and the effect of melanin on the penetration of the OCTA beam was not significant.

Optical coherence tomography angiography (OCTA) applications in ocular oncology

Optical coherence tomography angiography (OCTA) is a revolutionary method in the visualization of the vascular system in different retinal and choroidal layers. During the last 4 years since the commercial availability of different OCTA devices, attempts have been made to utilize this technology in various aspects of ocular oncology from the differentiation of benign and malignant lesions to assisting in evaluation of post-treatment complications, such as radiation retinopathy. However, current OCTA technology is restricted by various artefacts and inherent limitations, some of which are more pronounced in the presence of elevated tumoural lesions. Imminent advancements in OCTA systems and image acquisition processes promise a great potential for application of OCTA in ocular oncology.

Optical Coherence Tomography Angiography of Perilimbal Vasculature in Port-Wine Stain and Sturge-Weber Syndrome Patients

Purpose

To evaluate episcleral vasculature in corneal limbus with optical coherence tomography angiography (OCTA) in normal controls, port-wine stain (PWS) patients, and Sturge-Weber syndrome (SWS) patients.

Methods

Unilateral eyes from 18 normal controls (25.41 ± 4.00 years), 16 PWS patients (21.35 ± 11.05 years), and 8 SWS patients with ipsilateral late-onset glaucoma (22.13 ± 7.82 years). Each subject underwent slit-lamp examination, applanation tonometry, and OCTA. All OCTA scans were performed using an OCTA system operating at a wavelength of 1050-nm in four quadrants (superior, inferior, nasal, and temporal). The scans were delineated into conjunctival and episcleral layers using IMAGEnet6 for analysis.

Results

Slit-lamp and OCTA images demonstrated dense dilated episcleral vessels in PWS and SWS patients, particularly in the SWS group. The mean limbal involvements of episcleral vascular anomalies under slit lamp were respectively 0.00 ± 0.00, 5.44 ± 2.92, and 8.88 ± 2.70 clock hours in the control, PWS, and SWS groups (F = 58.46, P < 0.01). Quantitative analysis of OCTA scans showed that the episcleral vessel density in controls, PWS, and SWS groups were 25.03% ± 1.47%, 28.28% ± 1.96%, and 33.59% ± 3.00%, respectively (F = 18.17, P < 0.01). We also observed higher episcleral vessel diameter index in the SWS and PWS groups in comparison with the controls, particularly in the SWS group (P < 0.01). The vessel measurements, including density and diameter, were significantly correlated with the increased IOP and cup-to-disc (C/D) in SWS patients (P < 0.01).

Conclusions

To our knowledge, this is the first demonstration of OCTA in PWS and SWS patients and represents direct pathoanatomic evidence for episcleral alterations in SWS patients. The episcleral vessel measurements correlated with the increased IOP and C/D in SWS patients, indicating the episcleral vascular hypertrophy may be a risk factor for glaucoma in adult SWS patients.

Anterior segment optical coherence tomography angiography for iris vasculature in pigmented eyes

PURPOSE

To compare anterior segment optical coherence tomography angiography (AS-OCTA) systems in delineating normal iris vessels and iris neovascularisation (NVI) in eyes with pigmented irides.

METHODS

Prospective study from January 2019 to June 2019 of 10 consecutive patients with normal pigmented iris, had AS-OCTA scans with a described illumination technique, before using the same protocol in five eyes with NVI (clinical stages 1-3). All scans were sequentially performed using a spectral-domain OCTA (SD-OCTA), and a swept-source OCTA (SS-OCTA, Plex Elite 9000). Images were graded by two masked observers for visibility, artefacts and NVI characteristics. The main outcome measure was iris vessel density measurements comparing SS-OCTA and SD-OCTA systems.

RESULTS

The median age of subjects was 28 (20-35) years, and 50% were female. The paired mean difference of iris vessel density measurements was 11.7 (95% CI 14.7 to 8.1; p=0.002), SS-OCTA detecting more vessels than SD-OCTA. The inter-rater reliability for artefact score (κ=0.799, p<0.001) and visibility score (κ=0.722; p<0.001) were substantial. Both AS-OCTA systems were able to detect NVI vessels with a fair agreement (κ=0.588), with clearer NVI characteristics in stage 1/2 compared to stage 3 NVI (mean difference NVI score: 2.7±0.4, p=0.009).

CONCLUSION

The SS-OCTA was better able to delineate iris vessels in normal pigmented irides compared to SD-OCTA. Both AS-OCTA systems identified NVI characteristics based on its atypical configuration or location, but further improvements are needed to allow for more accurate objective, serial quantification for clinical use.

The Effectiveness of Ultrasound Biomicroscopic and Anterior Segment Optical Coherence Tomography in the Assessment of Anterior Segment Tumors: Long-Term Follow-Up

Background

Differential diagnosis and follow-up of small anterior segment tumors constitute a particular challenge because they determine further treatment procedures. The aim of this study was to evaluate the efficacy of the UBM (ultrasound biomicroscopy) and AS-OCT (anterior segment optical coherent tomography) in distinguishing different types of anterior segment lesions.

Methods

It was a retrospective, noncomparative study of case series of 89 patients with the suspicion of anterior segment tumor referred to the Ophthalmology Clinic, Medical University of Białystok, Poland, between 2016 and 2020. UBM was used to assess tumor morphology including height, location, and internal and external features. In cases in which UBM did not provide enough data, the AS-OCT images were analyzed. The data on demographics, best corrected visual acuity (BCVA), intraocular pressure (IOP), and rate of complications were also collected. Patients were followed up from 1 to 48 months.

Results

The mean observation period was 26.61 ± 16.13 months. Among the patients, there were 62 women and 27 men at a mean age of 55.59 ± 19.48 (range: from 20 to 89 years.) The types of tumors were cysts (41%), solid iris tumors (37.1%), ciliary body tumors (7.9%), peripheral anterior synechiae (PAS 3.4%), corneal tumors (4.5%), and others (5.6%). Patients with cysts were younger than patients with solid iris tumor (p=0.002). Women had a cyst as well as solid iris tumor more frequently than men, but less often a ciliary body tumor (p < 0.05). The horizontal size of tumor was positively correlated with patients' age (r_s = 0.38 and p=0.003) and negatively correlated with visual acuity (r_s = −0.42 and p=0.014). During the 4 years of diagnosis, only 2.2% of lesions exhibited growth (growth rate of 0.02 mm per year). Among 15 cases in which visualization with UBM was not satisfactory (mostly iris nevi), AS-OCT was helpful in diagnosis of 13 patients.

Conclusions

Both UBM and AS-OCT are effective methods in detection and diagnosis of tumors of the anterior eye segment, but in some cases, AS-OCT adds additional value to the diagnosis. Many lesions can be managed conservatively because they did not demonstrate growth during 4 years of the follow-up period.

Changes in Iris Perfusion Following Scleral Buckle Surgery for Rhegmatogenous Retinal Detachment: An Anterior Segment Optical Coherence Tomography Angiography (AS-OCTA) Study

Purpose: To investigate iris vasculature changes following scleral buckling (SB) surgery in eyes with rhegmatogenous retinal detachment (RRD) with anterior-segment (AS) optical coherence tomography angiography (OCTA). Methods: In this prospective study, enrolled subjects were imaged with an SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc., Dublin, CA, USA). Image acquisition of the iris was obtained using an AS lens and a manual focusing adjustment in the iris using the retina imaging software. The quantitative analysis was performed in eight different iris regions: (i) superior, (ii) supero-temporal, (iii) supero-nasal, (iv) nasal, (v) temporal, (vi) inferior, (vii) infero-temporal, (viii) infero nasal which, were defined as squares with area of 1.5 mm². Results: Fifteen eyes of 15 patients (six females; nine males) were included. Anterior segment optical coherence tomography angiography (AS-OCTA) parameters of the iris were statistically compared at baseline (preoperatively), 1 week, 1 month and 6 months after SB. At post-operative 1 week, perfusion density (PD) showed a significant decrease from 66.8 ± 13.2% to 58.55 ± 12.0% in the iris supero-nasal region (p = 0.016). However, at the 1-month follow-up visit, iris PD was significantly lower in all the analyzed iris regions, apart from the superior one. Conclusions: This study is the first description of AS-OCTA in patients undergoing SB. Our results showed a uniform reduction of the iris vessel network at 1 month after surgery, supporting the clinical use of AS-OCTA to identify early iris perfusion changes as potential predictive biomarkers of vascular disorders.

Vascular Density of the Anterior Segment of the Eye Determined by Optical Coherence Tomography Angiography and Slit-Lamp Photography

<b><i>Objective:</i></b> To determine the vascular density of the anterior segment (AS) of the eye from optical coherence tomography angiography (OCTA) images and slit-lamp photographs. <b><i>Methods:</i></b> A swept-source OCTA (Plex Elite 9000; Carl Zeiss) device modified with a +10-diopter lens was used to record the vasculature of the AS. Twenty eyes, including 4 eyes of 4 healthy subjects and 16 eyes of 12 patients scheduled for cataract surgery or combined vitrectomy and cataract surgery, were studied. The slit-lamp photographs of the AS were acquired concurrently with the AS-OCTA images. The vascular density was measured preoperatively and postoperatively in the nasal, temporal, superior, and inferior quadrants after binarization with ImageJ software. <b><i>Results:</i></b> Acceptable AS-OCTA images were obtained of 65% (superior), 80% (nasal), 70% (inferior), and 80% (temporal) of the eyes. The percentage of acceptable images was significantly lower in the superior quadrant among the AS-OCTA images than among the AS photographs (100%; <i>p</i> = 0.004). The vascular density determined by AS-OCTA was higher than that determined in the AS photographs in all quadrants (<i>p</i> = 0.011 to &#x3c;0.001). The AS-OCTA B-mode images showed that vascular flow was identified mainly between the conjunctiva and sclera but not in the ciliary body. The vascular density increased significantly after cataract surgery in the superior quadrant, which was significantly correlated with the location of the surgical incision (<i>p</i> = 0.03). <b><i>Conclusion:</i></b> AS-OCTA can obtain images with higher vascular density of the conjunctiva and sclera than slit-lamp photographs, and AS-OCTA images can show a postoperative increase in vascular density.

Optical coherence tomography angiography for marginal corneal vascular remodelling after pterygium surgery with limbal-conjunctival autograft

PURPOSE

To demonstrate the marginal corneal vascular remodelling using optical coherence tomography angiography (OCTA) after pterygium surgery.

METHODS

Twenty-two eyes of 19 patients (8 males, 11 females; age, 58.68 ± 0.34 years) with primary grade-T3 nasal pterygium were enroled in this study. The eyes underwent excision of the pterygium followed by a free limbal-conjunctival autograft. OCTA was performed in the nasal limbal area before surgery and at 10 days, 1 month, and 3 months after surgery. The scans were analyzed in terms of postoperative vascular remodelling of the autograft and marginal corneal vascular arcades (MCAs).

RESULTS

Preoperatively, the pterygium presented as abnormal centripetal vascular growth in OCTA scans. The conjunctival vessel density in the nasal quadrant was 29.26% ± 1.00%, 15.80% ± 0.83%, 19.80% ± 0.88%, and 20.26% ± 0.89% before and 10 days, 1 month, and 3 months, respectively, after surgery (F = 1.55, P < 0.01). The vessel density of MCAs was 28.33% ± 0.88%, 42.09% ± 0.41%, and 42.46% ± 0.31% 10 days, 1 month, and 3 months, respectively, after surgery (F = 188.2, P < 0.01).

CONCLUSIONS

We describe a new application of OCTA for MCA vasculature imaging. Vascular remodelling of the graft and MCAs appeared at 1 month and continued for 3 months after surgery.

Advances in Doppler optical coherence tomography and angiography

Since the first demonstration of Doppler optical coherence tomography (OCT) in 1997, several functional extensions of Doppler OCT have been developed, including velocimetry, angiogram, and optical coherence elastography. These functional techniques have been widely used in research and clinical applications, particularly in ophthalmology. Here, we review the principles, representative methods, and applications of different Doppler OCT techniques, followed by discussion on the innovations, limitations, and future directions of each of these techniques.

OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY DETECTS SUBCLINICAL RADIAL PERIPAPILLARY CAPILLARY DENSITY REDUCTION AFTER PLAQUE RADIOTHERAPY FOR CHOROIDAL MELANOMA

PURPOSE

To evaluate radial peripapillary capillary density (RPCD) in irradiated eyes without radiation papillopathy clinically.

METHODS

Patients treated with plaque radiotherapy for unilateral choroidal melanoma without radiation papillopathy clinically received optical coherence tomography and optical coherence tomography angiography imaging at ∼12- to 24-month follow-up. Comparison of RPCD globally and meridian closest to plaque and meridian farthest to plaque of irradiated versus nonirradiated eyes was performed.

RESULTS

Mean age was 55 years (n = 10). Mean largest basal diameter and thickness were 10.1 and 4.4 mm, respectively. Mean radiation dose to the optic nerve head and foveola was 41.7 and 66.2 Gy, respectively. No radiation papillopathy was detected by ophthalmoscopy throughout follow-up (mean:14 months). Radial peripapillary capillary density was significantly reduced globally (all P < 0.02). Meridian closest to plaque RPCD was significantly reduced (P < 0.01), but not meridian farthest to plaque RPCD (P = 0.07). Circumpapillary retinal nerve fiber layer thickness was not significantly reduced (P > 0.26). Radiation dose to the optic nerve head was correlated with meridian closest to plaque RPCD reduction (r = 0.76; P < 0.01). Mean radiation dose to the optic nerve head for <5% and ≥5% RPCD reductions was 35.9 ± 12.2 and 55.2 ± 6.4 Gy, respectively.

CONCLUSION

Radial peripapillary capillary density reduction was found in irradiated eyes before clinical evidence of radiation papillopathy and circumpapillary retinal nerve fiber layer thickness reduction. Radial peripapillary capillary density reduction is correlated to plaque location and radiation dose to the optic nerve head.

Association of Change in Iris Vessel Density in Optical Coherence Tomography Angiography With Anterior Segment Ischemia After Strabismus Surgery

Importance

Anterior segment ischemia (ASI) is a rare but potentially serious complication of strabismus surgery. Indocyanine green angiography and fluorescein angiography have been used to reveal iris-filling defects for clinicians considering a patient's risk of ASI. However, both are limited by invasive and time-consuming nature and potential adverse effects. Recently, optic coherence tomography angiography (OCT-A) has been introduced and used to image iris vasculature in individuals without abnormalities.

Objective

To determine the use of iris OCT-A for patients undergoing strabismus surgery and who are at risk for ASI.

Design, Setting, and Participants

This prospective case series study took place in an academic center. Adults undergoing strabismus surgery on at least 1 vertical muscle were prospectively recruited. The study took place from June to November 2017, and analysis began in January 2018.

Interventions

Indocyanine green angiography and OCT-A of the iris preoperatively and 1 day postoperatively.

Main Outcomes and Measures

A masked examiner evaluated all images and determined whether any filling defects were present qualitatively (lack of perfusion) and quantitatively (for OCT-A using internal software to calculate vessel density).

Results

Ten eyes of 9 individuals (mean [SD] age, 63 [11] years) were included. Two individuals (22.2%) identified as Hispanic, and 7 (77.8%) identified as white. There were 6 women (66.7%). The mean preoperative vessel density (percentage of the area occupied by vessels) averaged for all quadrants decreased from 57% preoperatively to 55% postoperatively (mean difference, 2%; 95% CI, 0.4%-4.2%; P = .05). When comparing quadrants adjacent to operated muscles, the mean vessel density decreased from 56% to 53% (mean difference, 2.6%; 95% CI, 0.17%-4.8%; P = .02). In addition, OCT-A detected vascular filling defects in the quadrant adjacent to the operated muscle on the patients in whom they were present (n = 1, inferior rectus recession).

Conclusions and Relevance

In this preliminary study, OCT-A determined iris vessel filling defects when present. In addition, OCT-A gives qualitative vessel density values that can be compared preoperatively and postoperatively although the clinical relevance of small differences is not known. While only 10 eyes were evaluated, and as such generalizability of these findings cannot be determined, the results suggest that OCT-A may be a useful tool in the evaluation of patients undergoing strabismus surgery to determine whether a patient is at risk to develop ASI.

Updates in imaging in ocular oncology

Innovations in ophthalmic imaging have made a profound impact on the diagnosis and treatment of ophthalmic disease. In ocular oncology, the development of optical coherence tomography with enhanced depth imaging and swept source technologies has made it possible to visualize the anatomical characteristics of retinoblastoma and uveal melanoma with a level of detail previously unobtainable on clinical exam alone. As a result, our understanding of the pathophysiology of vision loss in choroidal melanoma in particular has improved. These modalities have also helped identify fundoscopically “invisible” tumors and risk stratify pre-malignant choroidal lesions, making a strong case for their inclusion in all screening evaluations. Optical coherence tomography angiography, on the other hand, has allowed non-invasive imaging of the retinal and uveal vasculatures, providing insight into vascular changes associated with malignant transformation and vision loss following exposure to radiation. While the impact of new imaging technologies on clinical outcomes and overall survival in ocular oncology has yet to be determined, several reports cited herein offer promising results.

[Strabismus surgery and anterior segment ischemia syndrome]

The review summarizes the results of studies related to ischemia of the anterior segment of the eye after surgeries on straight extraocular muscles for strabismus and presents classification, clinical manifestations and risk factors for the development of the syndrome. The principal prevention measures for the clinically significant syndrome are focused on limiting the extent of surgical intervention: in the presence of risk factors and the need for intervention on more than two muscles - staged surgical treatment (i.e. ensuring a time interval between surgeries) that allows collateral circulation to form properly.

Anterior Segment Applications of Optical Coherence Tomography Angiography

Purpose: To review the current literature regarding optical coherence tomography angiography (OCT-A) applications in the anterior segment. Methods: A literature search was performed for terms including OCT-Angiography, anterior segment, cornea, conjunctiva, iris, applications and use in ophthalmology. Results: Fifteen studies were identified, 14 in human subjects. Studies with OCT-A of the conjunctiva, episclera, cornea, and iris were identified, some with normal eyes imaged and others with various pathologies. Most of these studies imaged corneal neovascularization. Three studies described protocols used for image acquisition, one of which was referenced by two later papers. Conclusions: OCT-A is a noninvasive technology with recent applications in the anterior segment. Several pilot studies have been performed on various anterior segment structures and disease states however standardization of image acquisition techniques is still needed. Future imaging could allow noninvasive and serial monitoring of pathology as well as recurrence after therapeutic intervention.

Quantitative analysis of conjunctival microvasculature imaged using optical coherence tomography angiography

Background

The goal was to quantitatively analyze the bulbar conjunctival microvascular density using optical coherence tomography angiography (OCTA) and compare it to the vessel density using functional slit-lamp biomicroscopy (FSLB).

Methods

Temporal bulbar conjunctiva of 20 eyes (10 healthy subjects) was imaged using both OCTA and FSLB. Image processing was performed including equalization, de-noising, thresholding, and skeletonization. The vessel density was measured by fractal analysis (box counting, Dbox) and pixel counting (%).

Results

Vessel density (Dbox) of the bulbar conjunctiva obtained using OCTA was 1.28 ± 0.01 Dbox, which was significantly lower than the result (1.32 ± 0.01 Dbox, P < 0.001) obtained using FSLB. Furthermore, the vessel density (%) obtained using OCTA was 3.31 ± 0.12%, which was also significantly lower than the result (3.69 ± 0.16%, P < 0.001) obtained using FSLB. No significant correlations (r ranged from 0.21 to 0.32, P > 0.05) between both instruments were found in both vessel density methods (Dbox and percentage). However, in each of the devices, vessel density in Dbox was significantly correlated with the vessel density in percentage (r = 1.0 for FSLB and r = 0.98 for OCTA, both P < 0.001).

Conclusion

This study demonstrated that the vessel density of the bulbar conjunctiva obtained using OCTA can be quantified, and the results were not compatible with that obtained using slit-lamp biomicroscopy photography.

Optical coherence tomography angiography for the anterior segment

Optical coherence tomography angiography (OCTA) is a rapid and non-invasive technique for imaging vasculature in the eye. As OCTA can produce high-resolution cross-sectional images and allow depth-resolved analysis for accurate localization of pathology of interest, it has become a promising method for anterior segment imaging. Furthermore, OCTA offers a more patient-friendly alternative to the conventional invasive dye-based fluorescent angiography. However, conventional OCTA systems are typically designed and optimized for the posterior segment of the eye, and thus using OCTA for anterior segment imaging can present several difficulties and limitations. In this review, we summarized the recent developments and clinical applications in anterior segment OCTA (AS-OCTA) imaging, such as for the cornea, iris, sclera and conjunctiva. We also compared commercially available OCTA systems, discussed the limitations of adapting current OCTA technology for the anterior segment imaging, and proposed possible future directions for AS-OCTA systems. AS-OCTA provides potential for future clinical applications such as diagnosis of corneal and iris pathologies, pre-operative surgical planning, assessment of new anti-angiogenic therapeutics or evaluation of limbal stem cell deficiency. With further development, OCTA for anterior segment imaging in the clinics may become common in the near future.

Conjunctival and Intrascleral Vasculatures Assessed Using Anterior Segment Optical Coherence Tomography Angiography in Normal Eyes

PURPOSE

To investigate conjunctival and intrascleral vasculatures using anterior segment optical coherence tomography angiography (AS-OCTA) in normal eyes.

DESIGN

Cross-sectional study.

METHODS

AS-OCTA images of the corneal limbus were acquired circumferentially using a swept-source optical coherence tomography system in 10 eyes of 10 healthy subjects. AS-OCTA flow patterns with en face maximum projection were compared between the superficial (from the conjunctival epithelium to a depth of 200 μm) and deep (from a depth of 200 μm to 1000 μm) layers. The OCTA images were also compared with fluorescein scleral angiography and indocyanine green aqueous angiography images. Quantitative parameters (vessel density, vessel length density, vessel diameter index, and fractal dimension) were compared among different locations.

RESULTS

The OCTA vessel patterns differed between the superficial and deep layers. The superficial-layer flow signals showed centrifugal patterns from the limbus, whereas the deep-layer flow signals showed segmental patterns. The OCTA en face images with whole signals had a similar appearance to the scleral angiography images, whereas those in the deep layer showed a similar appearance to the aqueous angiography images. In the superficial layer, only the vessel diameter index was significantly different among the locations (P = .003). In the deep layer, all 4 parameters differed significantly among the locations (P < .001 to P = .003).

CONCLUSIONS

OCTA is a promising tool for evaluating conjunctival and intrascleral vasculatures. It may also help in understanding ocular surface blood flow relevant to vascular and ocular surface diseases, as well as aqueous humor outflow.

Relationship between filtering bleb vascularization and surgical outcomes after trabeculectomy: an optical coherence tomography angiography study

PURPOSE

To explore the relationship between the bleb vasculature and surgical outcome after trabeculectomy (TRAB) using optical coherence tomography angiography (OCT-A).

METHODS

A prospective study was conducted, which included 26 eyes of 26 primary glaucoma patients in the final analysis. Thereinto, six patients underwent TRAB combined 5-FU and 12 patients received subconjunctival 5-FU injection postoperation. The bleb vessel was evaluated using OCT-A 1 week, 2 weeks, 1 month, 3 months, and 6 months after TRAB. Intraocular pressure (IOP), filtering bleb height, and bleb wall thickness were recorded at the same time. Pearson's correlation analysis and linear regression analysis were performed to determine the correlation of the vessel area data with other parameters.

RESULTS

Compared with vessel area 1 week after surgery, there was significant increase of the vessel area (△vessel area) 2 weeks (11.13 ± 11.91%, p < 0.05) and 1 month (16.91 ± 14.85%, p < 0.0001) after surgery in all patients. The △vessel area was significantly greater in acute angle closure (AAC) and primary angle closure glaucoma (PACG) 1-month post-TRAB as compared with that 1 week (p < 0.05). The results indicated that the △vessel area 1-month post-TRAB was positive correlated with IOP 6-month post-TRAB (β = 3.88, p = 0.042).

CONCLUSIONS

Filtering bleb vascularization evaluation using OCT-A could potentially predict IOP 6-month post-TRAB. Surgery effect predicted by filtering bleb vascularization detection is conducive to the select specific postoperative intervention to improve the success rate of TRAB.

Feasibility of correlation mapping optical coherence tomography angiographic technique using a 200 kHz vertical-cavity surface-emitting laser source for in vivo microcirculation imaging applications

Optical coherence tomography (OCT) angiography is a well-established in vivo imaging technique to assess the overall vascular morphology of tissues and is an emerging field of research for the assessment of blood flow dynamics and functional parameters such as oxygen saturation. In this study, we present a modified scanning-based correlation mapping OCT using a 200 kHz high-speed swept-source OCT system operating at 1300 nm and demonstrate its wide field-imaging capability in ocular angiographic studies.

Anterior segment optical coherence tomography for evaluation of cornea and ocular surface

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple. Several devices and technologies allow to explore and manage patients better. Optical coherence tomography (OCT) technology has evolved over the years, and hence a detailed evaluation of anterior segment (AS) structures such as cornea, conjunctiva, tear meniscus, anterior chamber, iris, and crystalline lens has been possible in a noncontact and safe procedure. The purpose of this special issue is to present and update in the evaluation of cornea and ocular surface, and this paper reviews a description of the AS-OCT, presenting the technology and common clinical uses of OCT in the management of diseases involving cornea and ocular surface to provide an updated information of the clinical recommendations of this technique in eye care practice.

Three-dimensional Hessian matrix-based quantitative vascular imaging of rat iris with optical-resolution photoacoustic microscopy in vivo

For the diagnosis and evaluation of ophthalmic diseases, imaging and quantitative characterization of vasculature in the iris are very important. The recently developed photoacoustic imaging, which is ultrasensitive in imaging endogenous hemoglobin molecules, provides a highly efficient label-free method for imaging blood vasculature in the iris. However, the development of advanced vascular quantification algorithms is still needed to enable accurate characterization of the underlying vasculature. We have developed a vascular information quantification algorithm by adopting a three-dimensional (3-D) Hessian matrix and applied for processing iris vasculature images obtained with a custom-built optical-resolution photoacoustic imaging system (OR-PAM). For the first time, we demonstrate in vivo 3-D vascular structures of a rat iris with a the label-free imaging method and also accurately extract quantitative vascular information, such as vessel diameter, vascular density, and vascular tortuosity. Our results indicate that the developed algorithm is capable of quantifying the vasculature in the 3-D photoacoustic images of the iris in-vivo, thus enhancing the diagnostic capability of the OR-PAM system for vascular-related ophthalmic diseases in vivo.

Optical coherence tomography angiography of a pigmented Fuchs' adenoma (age-related hyperplasia of the nonpigmented ciliary body epithelium) masquerading as a ciliary body melanoma

Purpose

To report a case of age-related hypertrophy of the nonpigmented ciliary epithelium (ARH-NPCE) clinically resembling a ciliary body melanoma and report the optical coherence tomography angiography (OCTA) findings associated with this lesion.

Observations

A 51-year-old male was referred for evaluation of a deeply pigmented ciliary body mass with extension through the iris root. Iridocyclectomy was performed due to concern for ciliary body melanoma. Histopathologic analysis was instead consistent with ARH-NPCE, also known as Fuchs' adenoma. Prior to surgery, OCTA images revealed abnormal vasculature in the area of the lesion. Vessels in the peripheral iris approaching the lesion appeared more tortuous and were non-radial as compared with normal iris vessels. The ciliary body mass itself could not be penetrated using an OCTA system operating at 1050 nm.

Conclusions and importance

ARH-NPCE may clinically resemble a pigmented ciliary body melanoma. This is the second case describing this clinical scenario, which may be more common than previously thought. Non-invasive imaging with OCTA revealed an abnormal peripheral iris vasculature pattern in the area of the iridociliary mass characterized by disorganized, tortuous, and non-radial vessels. Despite advances in longer wavelength OCTA systems, poor penetration of the ciliary body lesion precluded imaging of the intratumoral vessels in this location.

Anterior segment ischemia: etiology, assessment, and management

Anterior segment ischemia (ASI) is a potentially serious but rare complication of strabismus surgery. Among several risk factors, ASI occurs after strabismus surgery because of the nature of the anterior segment circulation. Disinsertion of rectus muscles leads to a decrease in the blood supply to the various anterior segment structures. We report a series of retrospective and prospective studies performed by our group focused on determining the risk of anterior segment ischemia following strabismus surgery, diagnosis, and modifications to surgical techniques to minimize the impact on anterior segment circulation. We found a significant decrease in postoperative anterior segment blood flow when operating vertical rectus muscles. Plication procedures preserve anterior segment circulation, and modifications to the technique allow the performance of adjustable sutures. Small adjustable selective procedures that spare the ciliary vessels have been demonstrated to be effective in patients with vertical and torsional diplopia. Ciliary sparing augmented adjustable transposition surgery decreases the risk of anterior segment ischemia while allowing management of potential post-operative alignment complications. Finally, ocular coherence tomography angiography is a valuable quantitative and qualitative technique to evaluate anterior segment ischemia. Strabismus surgeons should be aware of the risks of anterior segment ischemia when operating vertical rectus muscles. Modifications to standard surgical techniques allow surgeons to perform complex strabismus surgery in patients at risk for anterior segment ischemia.

Optical Coherence Tomography Angiography of Two Choroidal Nevi Variants

Optical coherence tomography angiography (OCT-A) is a recently established noninvasive technology for evaluation of the retinal and choroidal vasculature. The literature regarding the findings in choroidal nevi is scarce. We report the OCT-A findings associated with two different variants. Subject one had decreased vascular flow signal in the choroidal, choriocapillaris, deep retinal, and superficial retinal layers. Subject two had decreased vascular flow signal in the choroidal, choriocapillaris, and deep retinal layers with a normal vascular flow signal in the superficial retinal layer. To our knowledge, these patterns of decreased vascular flow signals have not been previously reported using OCT-A. This may be due to blockage from the choroidal nevus, true diminished blood flow (ischemia), or other factors.