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Optical coherence tomography angiography in dural carotid-cavernous sinus fistula
© The Author(s). 2016
Received: 28 December 2015
Accepted: 22 June 2016
Published: 7 July 2016
Recently, applications of optical coherence tomography angiography (OCTA) have been limited to the retina and posterior segment. Although early studies have described its use for other clinical applications, its role in anterior segment vasculature and optic disc imaging has been limited thus far.
We describe a novel clinical application of OCTA in a patient with dural carotid-cavernous sinus fistula (CCF), which was complicated by increased intra-ocular pressure (IOP). In this case report, we used the OCTA to delineate increased epsicleral venous flow in the affected eye with secondary raised IOP. Current measurements of episcleral venous pressure are either invasive or provide highly variable results, thus the OCTA may have the potential to provide a more reliable approach to assess episcleral vasculature. We also describe the use of OCTA to detect early glaucomatous nerve damage, associated with focal reductions in peripapillary retinal perfusion.
We present an early report of using OCTA of the anterior segment to allow rapid, non-invasive delineation of abnormal episcleral venous plexus secondary to dural CCF. The OCTA was also useful for detecting early reduction in peripapillary retinal perfusion, which suggests early glaucomatous optic neuropathy. This suggests that OCTA may have a role for determining risk of glaucoma in patients with CCF in future.
Anterior segment angiography has a variety of clinical applications, which may range from evaluation of corneal vascularization , to scleral inflammatory disorders [2, 3]. Optical coherence tomography angiography (OCTA) has been described for the delineation of vessels in the optic disc, retina and most recently, the anterior segment . These non-contact imaging systems detect phase variations or changes in reflectivity to detect vascular flow, with the added benefit of concurrently obtaining optical coherence tomography (OCT) scans of the surrounding tissue .
Since current OCTA systems are optimized for the retina and optic disc, we had previously described a technique adapted to perform scans in the anterior segment for normal corneal and limbal vessels . Carotid-cavernous sinus fistulas (CCF) result from abnormal connections between the carotid arterial system and the cavernous sinus, leading to ophthalmic complications due to arterialization of the ocular venous system . In this case report, we describe the use of OCTA to delineate the episcleral venous plexus, which may be the primary mechanism for secondary glaucoma in CCF.
The episcleral venous outflow is a key component of intraocular pressure, as embodied by the modified Goldmann equation, which can be thought of as the pressure required to move aqueous humor out of the eye through the resistance of the trabecular meshwork and the pressure in the episcleral veins . Optical coherence tomography angiography has been recently described for the delineation of blood flow within vessels in the optic disc, retina as well as a novel application in the anterior segment . Here, we used a novel OCTA technique, dedicated to the anterior segment, to explore a patient with a dural sinus CCF, due to abnormal connections between the carotid arterial system and the cavernous sinus .
One of the main presumed mechanisms for raised IOP associated with CCF is increased episcleral venous pressure . Objective measurements of episcleral venous pressure are either invasive or provide highly variable results . The OCTA may be a more reliable approach to assess episcleral vasculature. In addition, we have also used OCTA to image the optic disc to detect early glaucomatous nerve damage, which has been associated with reduced peripapillary retinal perfusion in focal areas around the disc . The potential clinical applications of OCTA for the anterior segment, apart from those already mentioned, could also extend to assessment of graft vascularization and inflammation , studying limbal vasculature associated with limbal stem cell deficiency or allergic eye disease , or even evaluation of bleb vascularity and morphology after glaucoma surgery .
In summary, this early clinical report describes, for the first time, the OCTA features in dural CCF, suggesting that OCTA allows rapid, non-invasive, in-depth visualization of abnormal episcleral vasculature in CCF. Further quantitative studies are needed to assess the link between abnormal episcleral vasculature and the risk for glaucoma in cases of dural CCF.
OCTA, optical coherence tomography angiography; OCT, optical coherence tomography; CCF, carotid-cavernous sinus fistula; IOP, intraocular pressure
Singhealth Foundation Research Grant (SHF/SG596P/2015)
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All authors made substantial contributions to conception and design, or acquisition of data, or analysis and interpretation of data (MA, CS, DM); been involved in drafting the manuscript or revising it critically for important intellectual content (MA, CS, DM); given final approval of the version to be published and have participated sufficiently in the work to take public responsibility for appropriate portions of the content (MA, CS, DM); and agreed to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved (MA, CS, DM).
The authors declare that they have no competing interests.
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