Although OCT angiography (OCT-A) is traditionally for imaging the microvasculature of the posterior segment, its use for imaging anterior segment structures is showing potential.1-5
Unlike current anterior segment assessment methods such as slit lamp and dye-based photography, which offer only a limited view of the vasculature, OCT-A can produce high-resolution cross-sectional images, detect vascularization even in cases of severe corneal opacification and the en face mode can produce frontal plane-oriented C-scans for viewing corneal pathology.1 The iris may also be a particularly strong candidate for en face OCT-A imaging because it’s flat, thin and easily accessible, though one study found visualization of non-clinically visible vessels depends heavily on iris pigmentation.5
Recently, a study expanded the list of potential anterior segment applications for OCT-A to include the assessment of melanocytic lesions of the conjunctiva and iris.6 The cross-sectional study included 25 patients with untreated conjunctival lesions (five melanoma, 13 nevus, seven primary acquired melanosis) and 52 with untreated iris lesions (10 melanoma and 42 nevus).
The researchers obtained good OCT-A images in 18 of the 25 conjunctival lesion patients and in 42 of the 52 iris lesion patients. Mydriasis and unfavorable lesion location resulted in failure to capture good images; patient cooperation was another failure factor, as OCT-A is notoriously sensitive to motion.7
Nevertheless, OCT-A detected vascular structures in all conjunctival lesions and in 77% of iris lesions. The researchers found that the conjunctival melanoma and nevi demonstrated the same intralesional tortuous patterns, while vasculature in eyes with primary acquired melanosis was similar to that of the normal conjunctiva. Iris melanoma and nevi also demonstrated similar tortuous patterns, which were distinct from the radially oriented patterns of normal iris vasculature.
The researchers observed that light pigmentation, patient cooperation and bulbar rather than caruncular location for conjunctival lesions tended to yield good quality images. They found no differentiating patterns in vascular density between nevi and conjunctival or iris melanoma.
Overall, OCT-A was successful in imaging the vasculature of melanocytic lesions of the conjunctiva and iris, but the researchers found it wasn’t possible to differentiate between benign and malignant lesions. They stated that new software is needed to improve image acquisition and analysis.
1. Lee WD, Devarajan K, Chua J, et al. Optical coherence tomography angiography for the anterior segment. Eye and Vision. February 1, 2019. [Epub ahead of print].
2. Ang M, Sim DA, Keane PA, et al. Optical coherence tomography angiography for anterior segment vasculature imaging. Ophthalmology. 2015;122:1740-7.
3. Ang M, Cai Y, Shahipasand S, et al. En face optical coherence tomography angiography for corneal neovascularization. Br J Ophthalmology. 2016;100:616-21.
4. Ang M, Cai Y, Tan AC. Swept source optical coherence tomography angiography for contact lens-related corneal vascularization. J Ophthalmology. September 26, 2016. [Epub ahead of print].
5. Roberts PK, Goldstein DA, Fawzi AA. Anterior segment optical coherence tomography for identification of iris vasculature and staging of iris neovascularization: A pilot study. Curr Eye Res. 2017;42:8:1136-42.
6. Brouwer NJ, Marinkovic M, Bleeker JC, et al. Anterior segment OCTA of melanocytic lesions of the conjunctiva and iris. Am J Ophthalmol. September 12, 2020. [Epub ahead of print].
7. De Oliveira PRC, Berger AR, Chow DR. Optical coherence tomography angiography in chorioretinal disorders. Can J Ophthalmology. 2017;52:1:125-36.