Using swept-source OCT and OCT angiography to image choroidal tumours

September 17, 2020

SS-OCT provides a clear view of the eye’s internal structures and any abnormalities, helping to differentiate benign from malignant lesions.

Compared with traditional spectral domain optical coherence tomography (SD-OCT), swept-source OCT (SS-OCT) allows us to image the eye’s deep tissues with excellent fidelity and consistency. The technology’s rapid scanning speed and targeted wavelength helps us to visualise the choroid and sclera in remarkable detail, and enables us to acquire 6, 9 and 12 mm scans in a fast and efficient manner.

Recently, we collaborated to investigate the use of SS-OCT and in particular, swept source OCT angiography (SS-OCTA*) to differentiate between a range of intraocular tumours. Over the course of our study, we used our imaging platform (DRI OCT Triton, Topcon Medical Systems) to capture detailed images that helped us to find evidence-supported diagnoses and treatment plans.

In our prospective study, we evaluated 40 intraocular tumours, including 16 choroidal nevi, ten melanomas, six choroidal hemangiomas, three choroidal metastasis, three retinal haemangioblastomas and two melanocytomas. All patients enrolled in the study underwent a complete ophthalmic evaluation including ultrasound, SS-OCTA and fluorescein angiography. To help the reader to better understand the value of swept source technology, we are pleased to share case details and images.

Choroidal nevi and melanoma

For choroidal nevi, we typically found a dome-shaped lesion associated with choriocapillaris compression and choroidal shadowing. In a representative case (Figure 1A-C), we encountered retinal pigment epithelium (RPE) irregularities which indicated the presence of drusen, thus demonstrating the chronicity of these lesions (Figure 1B and C). We also see marked photoreceptor loss (Figure 1C). OCTA analysis shows a more hyperreflective ring than the centre of the lesion in the superficial capillary plexus map (Figure 1A).

This is supported by corresponding fundus photography (Figure 1B). Both images, as well as additional visualisations, are produced by the SS-OCTA platform in very little time.

For choroidal melanoma, however, differences emerge. In this case (Figure 2A-D), we identified a dome-shaped lesion in addition to compression of the choriocapillaris. There is still choroidal shadowing, but these lesions also typically present intraretinal oedema, shaggy photoreceptors, loss of photoreceptors and subretinal fluid (Figure 2D).

OCTA demonstrates that these conditions present observable artefacts because the subretinal fluid is present (Figure 2A and B). We are currently investigating additional cases to try to correlate these patterns with tumour growth and possibly, metastasis. Hyperreflectivity and vascular patterns can likely be correlated with prognosis, but more confirmatory research is needed.

Choroidal haemangiomas

For choroidal haemangiomas (Figure 3A-D), we often observed a dome-shaped lesion associated with chronic RPE and cystic changes. There is no compression of the choriocapillaris. We also see dilated choroidal vessels, a hallmark in structural OCT visualisation (Figure 3A) given the large vessels that correlate with histopathology.

In this example, we see that OCTA (Figure 3C-D) shows a hyper-reflectivity of vessels. However, the areas lacking observable flow could also represent large vessels with slow flow. After treatment, the pattern of hyperreflectivity decreases in the periphery.1 In some patients, certain vessels can be detected in the central retina.

Choroidal metastasis

Choroidal metastasis (Figure 4A-C) is another type of lesion SS-OCT can help differentiate. It presents as a lumpy, bumpy, contour-like lesion, often with granular changes of the RPE.1 There are empty spaces between the neurosensory retina and RPE. Additionally, there is tumour-infiltrated choroid, as well as hyperreflective points/dots in the external retina on the tumour.

The example in Figure 4 shows the metastatic lesion (Figure 4A) and hyperreflective pinpoint lesions on the retina (Figure 4B) with a bumpy appearance and visible subretinal fluid (Figure 4C). When patients like these are treated (with systemic chemotherapy), we see better visibility of the choroidal vessels because of RPE atrophy. After the treatment, large choroidal vessels become apparent on OCT-A (Figure 4D; shown here from another patient).

Melanocytomas and haemangioblastomas

A melanocytoma is a bilobular mass with highly pigmented choroidal vessels protruding through the lamina cribrosa.1 These tumours are often characterised by posterior shadowing, as well as cystic changes between the normal retina and melanocytoma lesion (Figure 5AD). The lesions typically appear with hyperreflectivity of the tumour’s vessels on the surface.

OCTA images (Figure 5A-B) show that the diameter of the tumour can be delineated (see yellow colouring), whilst the violet colouring shows the areas in which flow of the lesion is detected both in the retinal superficial and deep plexus. OCTA images (Figure 5A-B) show relative hyporeflectivity of the lesion, but there are some superficial vessels that can be seen here as well. We monitor these vessels for potential malignant transformation.

A haemangioblastoma is generally an exophytic mass protruding from the internal retina. There is exudation and large vessels from the optic disc can extend to the periphery, which are the classical feeder vessels (Figure 6A-E). There are hyperreflective dots on the external layers of the retina that correspond to exudation (Figure 6A-B).

The posterior hyaloid seems to be, in most of the cases, very strongly attached, creating traction in these vascular tumours; this traction and exudation can decrease after treatment and after posterior vitreous detachment (Figure 6A-B). Figure 6D depicts OCTA, demonstrating the feeder vessels and alterations of foveal avascular zone in the superficial and deep vascular plexus after treatment.

Concluding thoughts

Ultimately, SS-OCT provides clinicians a clear view on internal structures and abnormalities, allowing us to measure and compare with confidence. In a way, SS-OCT functions like an optical biopsy of intraocular tumours, helping us differentiate between benign and malignant lesions. In the future, SS-OCT, particularly with OCTA functionality, could play an important role in helping to differentiate, diagnose, prognosticate and manage intraocular tumours.

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J. Fernando Arevalo, MD PhD FACS
E: arevalojf@jhmi.edu
Dr Arevalo is the Edmund F. and Virginia B. Ball professor of ophthalmology and chairman at the Department of Ophthalmology, Johns Hopkins Bayview Medical Center, Wilmer Eye Institute, and at the Johns Hopkins University School of Medicine in Baltimore, Maryland, United States. He has received grant research funds from Topcon.

Dr Juan David Arias, MD
Dr Arias is associate professor of Retina & Vitreous/Oncology at the Universidad Autónoma de Bucaramanga, Foscal Internacional Floridablanca, Santander, Colombia. He has no financial disclosures.

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Reference

  1. Cennamo G, Romano MR, Breve MA, Velotti N, Reibaldi M, de Crecchio G, Cennamo G. Evaluation of choroidal tumors with optical coherence tomography: enhanced depth imaging and OCT-angiography features. Eye (Lond). 2017;31:906-915.

*Topcon OCTA technology is not cleared for sale in the United States.