Abstract
BackgroundWith an increased number of papers on how to interpret optical coherence tomography angiography (OCTA) findings in uveitis, the aim of this review is to assess its efficacy for the quantitative monitoring of structural and functional changes in inflamed conjunctiva and iris vessels in patients with acute anterior uveitis and iris neovascularization.Main bodyOCTA, currently designed as a retinal vascular imaging system, has been recently adapted for anterior segment and showed good potential for successful imaging of the conjunctiva, the cornea, and the iris. OCTA can successfully delineate corneal vessels with substantial image quality. At the same time, it can detect changes in conjunctival and limbal vascularization and thus can be applied to pseudo-inflammatory conditions such as pterygium. Anterior segment OCTA allows analysis of iris vasculature and 3-D reconstruction of the normal iris vessels. OCTA can determined iris vessel filling defects or their flow increase, when present, secondary to inflammatory conditions. In addition, OCTA gives qualitative vessel density values that can be compared pre- and post-anti-inflammatory treatment. OCTA for imaging of the iris vasculature in health and disease is highly dependent on iris pigmentation. In both OCTA and fluorescein angiography, iris pigmentation causes vasculature imaging blockage, but OCTA provides more detailed iris vasculature images. Fine, clinically invisible iris vessels can be visualized by OCTA in the very early stages as well as in the regressed stage of NVI. Additional studies including different iris pathologies are needed to determine the most optimal scanning parameters in OCTA of the anterior segment.ConclusionsThis review aims to establish the current application of OCTA to anterior segment disorders of the eye, with an emphasis on exploring its use in iris vessel dilation seen in various forms of iritis, as a predictive factor for further episodes of inflammation. In addition, OCTA can depict neovascularization of the iris secondary to proliferative diabetic retinopathy.
Highlights
Techniques for anterior segment optical coherence tomography angiography (OCTA) acquisition For anterior segment imaging, depending on the OCTA device, an anterior segment lens may be necessary
(See figure on previous page.) Fig. 1 Anterior segment OCTA of four pterygia shows dilated and anomalous coiled vessels that differ from the smaller vessels of normal conjunctiva
The most relevant step forward of OCT has been its evolution from assessing the morphology of a tissue to studying its functional component, through optical coherence tomography angiography (OCTA) [1]
Summary
Techniques for anterior segment OCTA acquisition For anterior segment imaging, depending on the OCTA device, an anterior segment lens may be necessary. With an increased number of papers on how to interpret optical coherence tomography angiography (OCTA) findings in uveitis, the aim of this review is to assess its efficacy for the quantitative monitoring of structural and functional changes in inflamed conjunctiva and iris vessels in patients with acute anterior uveitis and iris neovascularization. The most relevant step forward of OCT has been its evolution from assessing the morphology of a tissue to studying its functional component, through optical coherence tomography angiography (OCTA) [1] This is a technique that creates images of capillary networks by comparing the amount of light returned from static and mobile targets without the need for intravenous dye administration [2]. The purpose of this review is to summarize the current OCTA application to the anterior segment of the eye, with emphasis on how to use it to assess iris vascular changes in anterior uveitis
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