Optical coherence tomography angiography in dural carotid-cavernous sinus fistula

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.

CAROTID CAVERNOUS SINUS FISTULA FINDINGS IN OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY BEFORE AND AFTER PERCUTANEOUS EMBOLIZATION

BACKGROUND/PURPOSE

Optical coherence tomography angiography has been used to evaluate the posterior segment in a wide variety of pathologies because it is a noninvasive image technique, but its role in the evaluation of the retina in a case of carotid cavernous sinus fistula has not been described yet.

METHODS RESULTS

We present a patient who consulted with spontaneous left superior eyelid hematoma and was diagnosed with left indirect carotid cavernous sinus fistula. In this study, optical coherence tomography angiography was used to evaluate the different macular capillary plexuses in a patient with carotid cavernous sinus fistula and a clinical situation of secondary local venous stasis before and after percutaneous embolization. Augmented vessel density was seen in superficial and deep capillary plexuses and in choriocapillaris before the percutaneous embolization, and a decrease of the parameters was seen after the treatment.

CONCLUSION

All macular capillary plexuses presented with augmented vessel density levels that normalized after treatment. These findings were previously undescribed, and they suggest that optical coherence tomography angiography may be useful to initially evaluate patients with carotid cavernous sinus fistula who are planned to undergo embolization and to follow them up until normalization of the vascular structures is reported.

Microvascular and neural alterations in carotid cavernous fistulas: An optical coherence tomography angiography study

BACKGROUND

Current modalities for diagnosing carotid cavernous fistula (CCF) are inaccurate in analysing retinal microcirculations and nerve fibre changes. Retinal microvascular and neural alterations occur in CCF patients and can be quantitatively measured using optical coherence tomography angiography (OCTA). We measured the neurovascular changes in the eyes of CCF patients and used OCTA as a supplementary method.

METHODS

This cross-sectional study studied 54 eyes of 27 unilateral CCF subjects and 54 eyes of 27 healthy age- and sex-matched controls. OCTA parameters in the macula and optic nerve head (ONH) were analysed using a one-way analysis of variance with further Bonferroni corrections. Parameters with statistical significance were included in a multivariable binary logistic regression analysis and receiver operating characteristic (ROC) curves were generated.

RESULTS

There was significantly less deep-vessel density (DVD) and ONH-associated capillary density in both eyes of CCF patients than in controls, while the differences between the affected and contralateral eyes were insignificant. The retinal nerve fibre layer and ganglion cell complex thickness were lower in the affected eyes than in the contralateral or controlled eyes. ROC curves identified DVD and ONH-associated capillary density as significant parameters in both eyes of CCF patients.

CONCLUSION

The retinal microvascular circulation was affected in both eyes of unilateral CCF patients. Microvascular alterations occurred before retinal neural damage. This quantitative study suggests a supplementary measurement for diagnosing CCF and detecting early neurovascular impairments.

Glaucoma and Myopia: Diagnostic Challenges

The rising global prevalence of myopia is a growing concern for clinicians, as it predisposes patients to severe ocular pathologies including glaucoma. High myopia can be associated with clinical features that resemble glaucomatous damage, which make an accurate glaucoma diagnosis challenging, particularly among patients with normal intraocular pressures. These patients may also present with established visual field defects which can mimic glaucoma, and standard imaging technology is less useful in disease detection and monitoring due to the lack of normative data for these anatomically unique eyes. Progression over time remains the most critical factor in facilitating the detection of early glaucomatous changes, and thus careful longitudinal follow-up of high-risk myopic patients is the most important aspect of management. Here, we review our current understanding of the complex relationship between myopia and glaucoma, and the diagnostic challenges and limitations of current testing protocols including visual field, intraocular pressure, and imaging. Furthermore, we discuss the clinical findings of two highly myopic patients with suspected glaucoma.

Global trends and frontiers of research on pathologic myopia since the millennium: A bibliometric analysis

Background and purpose

Pathologic myopia (PM) is an international public health issue. This study aimed to analyze PM research trends by reporting on publication trends since 2000 and identifying influential journals, countries, authors, and keywords involved in PM.

Methods

A bibliometric analysis was performed to evaluate global production and development trends in PM since 2000 and the keywords associated with PM.

Results

A total of 1,435 publications were retrieved. PM has become a fascinating topic (with relative research interest ranging from 0.0018% in 2000 to 0.0044% in 2021) and a global public health issue. The top three countries with the highest number of publications were China, the USA, and Japan. The journals, authors, and institutions that published the most relevant literature came from these three countries. China exhibited the most rapid increase in the number of publications (from 0 in 2000 to 69 in 2021). Retina published the most papers on PM. Kyoko Ohno-Matsui and Tokyo Medical and Dental University contributed the most publications among authors and institutions, respectively. Based on keyword analysis, previous research emphasized myopic choroidal neovascularization and treatment, while recent hotspots include PM changes based on multimodal imaging, treatment, and pathogenesis. Keyword analysis also revealed that deep learning was the latest hotspot and has been used for the detection of PM.

Conclusion

Our results can help researchers understand the current status and future trends of PM. China, the USA, and Japan have the greatest influence, based on the number of publications, top journals, authors, and institutions. Current research on PM highlights the pathogenesis and application of novel technologies, including multimodal imaging and artificial intelligence.

Pathologic myopia: advances in imaging and the potential role of artificial intelligence

Pathologic myopia is a severe form of myopia that can lead to permanent visual impairment. The recent global increase in the prevalence of myopia has been projected to lead to a higher incidence of pathologic myopia in the future. Thus, imaging myopic eyes to detect early pathological changes, or predict myopia progression to allow for early intervention, has become a key priority. Recent advances in optical coherence tomography (OCT) have contributed to the new grading system for myopic maculopathy and myopic traction maculopathy, which may improve phenotyping and thus, clinical management. Widefield fundus and OCT imaging has improved the detection of posterior staphyloma. Non-invasive OCT angiography has enabled depth-resolved imaging for myopic choroidal neovascularisation. Artificial intelligence (AI) has shown great performance in detecting pathologic myopia and the identification of myopia-associated complications. These advances in imaging with adjunctive AI analysis may lead to improvements in monitoring disease progression or guiding treatments. In this review, we provide an update on the classification of pathologic myopia, how imaging has improved clinical evaluation and management of myopia-associated complications, and the recent development of AI algorithms to aid the detection and classification of pathologic myopia.

Anterior Segment Optical Coherence Tomography Angiography Following Trabecular Bypass Minimally Invasive Glaucoma Surgery

Objective

To assess anterior segment optical coherence tomography angiography (AS-OCTA) imaging of the episcleral vessels before and after trabecular bypass minimally invasive glaucoma surgery (MIGS).

Design

A prospective, clinical, single-centre, single-arm pilot feasibility study conducted at National University Hospital, Singapore.

Subjects

Patients with primary glaucomatous optic neuropathy undergoing Hydrus Microstent (Ivantis Inc., Irvine, CA, USA) implantation, who require at least one intra-ocular pressure-lowering medication. One or two eyes per patient may be enrolled.

Methods

We performed AS-OCTA (Nidek RS-3000 Advance 2, Gamagori, Japan) pre- and up to 6 months post-MIGS implantation using a standard protocol in all cornealimbal quadrants, to derive episcleral vessel densities (VD) using a previously described technique.

Main Outcome Measures

Episcleral VD pre- and post-surgery, in sectors with and without the implant.

Results

We obtained serial AS-OCTA images in 25 eyes undergoing MIGS implantation (23 subjects, mean age 70.3 ± 1.5, 61% female) with mean preoperative intraocular pressure (IOP) of 15.5 mmHg ± 4.0. We observed reductions in postoperative episcleral VD compared to preoperative VD at month 1 (mean difference −3.2, p = 0.001), month 3 (mean difference −2.94, p = 0.004) and month 6 (mean difference −2.19, p = 0.039) in sectors with implants (overall 6 month follow-up, p = 0.011). No significant changes were detected in episcleral VD in the sectors without implants (p = 0.910).

Conclusion

In our pilot study, AS-OCTA was able to detect changes in the episcleral VD following trabecular bypass MIGS, which may be a useful modality to evaluate surgical outcomes if validated in future studies.

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.

Role of anterior segment optical coherence tomography angiography in the assessment of acute chemical ocular injury: a pilot animal model study

To examine the use of anterior segment-optical coherence tomography angiography (AS-OCTA) in the assessment of limbal ischemia in an animal model chemical ocular injury. We conducted a prospective study using an established chemical ocular injury model in 6 rabbits (12 eyes), dividing the cornea limbus into 4 quadrants. Chemical injury grade was induced based on extent of limbal injury (0 to 360 degrees) and all eyes underwent serial slit-lamp with AS-OCTA imaging up to one month. Main outcome measure was changes in AS-OCTA vessel density (VD) comparing injured and control cornea limbal quadrants within 24 h and at one month. AS-OCTA was able to detect differences in limbal VD reduction comparing injured (3.3 ± 2.4%) and control quadrants (7.6 ± 2.3%; p < 0.001) within 24 h of ocular chemical injury. We also observed that AS-OCTA VD reduction was highly correlated with the number of quadrants injured (r = − 0.89; p < 0.001; 95% CI − 5.65 to − 1.87). Corneal vascularization was detected by AS-OCTA in injured compared to control quadrants (10.1 ± 4.3% vs 7.0 ± 1.2%; p = 0.025) at 1 month. Our animal pilot study suggests that AS-OCTA was able to detect limbal vessel disruption from various severities of acute chemical insult, and in the future, could potentially serve as an adjunct in providing objective grading of acute ocular chemical injury once validated in a clinical trial.

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 in Patients Following Cultivated Oral Mucosal Epithelial Transplantation

PURPOSE

To analyze corneal neovascularization using anterior segment optical coherence tomography angiography (AS-OCTA) in patients following cultivated oral mucosal epithelial sheet transplantation (COMET).

DESIGN

Observational case series.

METHODS

Nine eyes in 7 patients were analyzed. Four images of corneal quadrant were obtained by AS-OCTA from each patient during follow-up post-COMET in the Department of Ophthalmology at Osaka University Hospital. The depth of corneal neovascularization was evaluated using en face and B-scan images. Each quadrant image was classified as 1 of the following 5 types: stromal, predominantly stromal, epithelial, predominantly epithelial, or avascular. The image quality of slit-lamp photography and AS-OCTA was graded from 0 to 4. Manually segmented images of the epithelial and stromal vessels were obtained.

MAIN OUTCOME MEASURES

Depth and image quality of corneal neovascularization following COMET.

RESULTS

Six patients were male and 1 was female. The mean patient age was 61.3 ± 19.1 years. Thirty-six quadrant images were obtained, of which 4 (11.1%) were stromal, 16 (44.4%) were predominantly stromal, 3 (8.3%) were epithelial, 11 (30.6%) were predominantly epithelial, and 2 (5.6%) were avascular. The image quality obtained by AS-OCTA was significantly better than that obtained by slit-lamp photography (2.38 ± 0.94 vs 2.03 ± 0.90; P = .021). Segmentation images clearly demonstrated both epithelial and stromal vasculatures individually.

CONCLUSIONS

AS-OCTA is useful for evaluation of depth of corneal neovascularization and has the potential to distinguish between conjunctivalization and stromal neovascularization following COMET. Findings on AS-OCTA could contribute to clinical decision making, given that retreatment is required for conjunctivalization after COMET.

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.

Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model

Corneal neovascularization (CoNV) could be treated by novel anti-angiogenic therapies, though reliable and objective imaging tools to evaluate corneal vasculature and treatment efficacy is still lacking. Optical coherence tomography angiography (OCTA) -currently designed as a retinal vascular imaging system- has been recently adapted for anterior-segment and showed good potential for successful imaging of CoNV. However, further development requires an animal model where parameters can be studied more carefully with histological comparison. Our study evaluated the OCTA in suture-induced CoNV in a rabbit model compared to indocyanine green angiography (ICGA) and slit-lamp photography (SLP). Overall vessel density measurements from OCTA showed good correlation with ICGA (0.957) and SLP (0.992). Vessels density by OCTA was higher than ICGA and SLP (mean = 20.77 ± 9.8%, 15.71 ± 6.28% and 17.55 ± 8.36%, respectively, P < 0.05). OCTA was able to depict CoNV similarly to SLP and ICGA, though it could better detect small vessels. Moreover, the depth and growth of vessels could be assessed using en-face and serial-scans. This study validated the OCTA in a rabbit model as a useful imaging tool for translational studies on CoNV. This may contribute to further studies on OCTA for anterior-segment including serial evaluation of emerging anti-angiogenic therapies.

A rare case of bilateral spontaneous indirect caroticocavernous fistula treated previously as a case of conjunctivitis

Carotid cavernous fistula is an abnormal communication between the carotid arterial system and the cavernous sinus. We present an interesting, rare case of bilateral spontaneous ‘Barrow type- C’ fistula treated presumptively as conjunctivitis. A 66 year old patient presented in the eye casualty at North Devon District Hospital in January 2016, referred from her General practitioner complaining of bilateral red eyes. She was found to have large, prominently diffused and engorged scleral blood vessels on both sides along with raised intraocular pressures of 26mm of Hg bilaterally. The patient was diagnosed with an indirect carotic cavernous fistulas bilaterally in view of the clinical and radiology findings. Barrow type - C dural fistulas were reported to be seen bilaterally on radiology findings. Patient was referred for interventional treatment to the closest neurosurgical center where she had four failed attempts of coil embolization after which she was referred to a second neurosurgery center at Bristol where she underwent successful coil catheterization as the treatment for her carotid cavernous fistula. Indirect carotid cavernous fistula most commonly occur spontaneously. Bilateral spontaneous indirect carotid cavernous fistula is a very rare diagnosis and and there are very few cases reported in the literature without an underlying etiology or a known cause like Ehlers -Danlos syndrome or diabetes mellitus. Bilateral spontaneous carotid cavernous fistulas are difficult to diagnose due to mild symptoms and no history of trauma. We conclude that carotid cavernous fistulas are a threat to the vision if left untreated due to delayed diagnosis. We recommend considering bilateral carotid cavernous fistula as a differential diagnosis in patients with an ongoing history of red eyes or those unresponsive to conventional topical treatment for conjunctivitis like symptoms.

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 anterior segment optical coherence tomography angiography systems for corneal vascularisation

Aim

To newly describe a spectral-domain (SD) optical coherence tomography angiography (OCTA) for the cornea and directly compare two OCTA system scans of the same eyes with corneal vascularisation.

Methods

Cross-sectional, observational, comparative case series. We performed sequential OCTA scans (10 eyes of 10 subjects with corneal vascularisation,4 scans each eye) repeated using split-spectrum amplitude decorrelation algorithm angiography system (SSADA, AngioVue; Optovue Inc, USA) and SD OCTA (Angioscan; Nidek Co. Ltd, Japan) in the same region of interest. We analysed all scan images for repeatability, image quality and vessel density measurements and compared OCTA systems.

Results

We obtained substantial interobserver repeatability in terms of image quality score (κ=0.86) for all 80 OCTA scans (median age 49 years, 50% women). The correlation was moderately good (r=0.721) when comparing vessel density measurements between OCTA systems, but greater in the SSADA compared with SD OCTA system (mean vessel density 20.3±4.9% vs 15.1±4.2%, respectively; p<0.001).

Conclusion

In this pilot clinical study, we describe successful delineation of corneal vessels with substantial image quality using a new SD OCTA system. The vessel density measurements were greater using the SSADA compared with SD OCTA system in the same area of corneal vascularisation. Further studies are required to confirm the advantages, limitations and differences between these OCTA systems for the anterior segment.

Swept Source Optical Coherence Tomography Angiography for Contact Lens-Related Corneal Vascularization

Purpose. To describe a novel technique of adapting a swept-source optical coherence tomography angiography (OCTA) to image corneal vascularization. Methods. In this pilot cross-sectional study, we obtained 3 × 3 mm scans, where 100,000 A-scans are acquired per second with optical axial resolution of 8 μm and lateral resolution of 20 μm. This was performed with manual “XYZ” focus without the anterior segment lens, until the focus of the corneoscleral surface was clearly seen and the vessels of interest were in focus on the corresponding red-free image. En face scans were evaluated based on image quality score and repeatability. Results. We analyzed scans from 10 eyes (10 patients) with corneal vascularization secondary to contact lens use in 4 quadrants, with substantial repeatability of scans in all quadrants (mean image quality score 2.7 ± 0.7; κ = 0.75). There was no significant difference in image quality scores comparing quadrants (superior temporal: 2.9 ± 0.6, superior nasal: 2.8 ± 0.4, inferior temporal: 2.5 ± 0.9, and inferior nasal: 2.4 ± 1.0; P = 0.276) and able to differentiate deep and superficial corneal vascularization. Conclusion. This early clinical study suggests that the swept-source OCTA used may be useful for examining corneal vascularization, which may have potential for clinical applications such as detecting early limbal stem cell damage.