Optical Coherence Tomography Angiography (OCTA) after Plaque and Proton Beam Radiotherapy for Uveal Melanoma

Abstract

Purpose : Uveal melanoma is the most common primary intraocular tumor in adults and is a potentially life-threatening malignancy. Focal radiation therapy has been widely utilized to reduce tumor growth and can induce varying degrees of radiation retinopathy.^1,2 We conducted a prospective study using OCTA to analyze the parafoveal superficial capillary plexus following radiation for uveal melanoma.

Methods : 21 subjects were imaged using the OCTA RTVUe XR 100 Avanti (OptoVue, Inc., Fremont, CA). 3x3mm scans were averaged to improve signal-to-noise ratio.³ Axial lengths and SD-OCT imaging facilitated lateral scaling and comparison analysis. Boundaries of the foveal avascular zone (FAZ) were delineated manually in ImageJ (NIH, Bethesda, MD) by two masked observers. FAZ area and acircularity were determined using MATLAB (Mathworks, Natick, MA).^4,5

Results : OCTA qualitatively demonstrated areas of reduced capillary density in post-radiation eyes (Fig 1). Quantitative analysis was precluded by fixation errors and image artifact in 48% of subjects; 11 were included for analysis (8 plaque, 3 proton beam). Patients were imaged at a mean of 30.1±26.7months following radiation with an average tumor height of 2.8±1.5mm and radiation dose of 25.9±35.8Gy at the fovea. The average FAZ area for the irradiated and nonirradiated eyes was 260±132µm² and 176±85µm², respectively (p=0.10). Comparing the acircularity of irradiated to nonirradiated eyes revealed a mean of 1.37±0.23 and 1.28±0.19, respectively (p=0.34). Irradiated metrics were compared to a previously obtained normative database of 232 eyes with a mean FAZ area of 250±104µm² (p=0.81), and a mean acircularity of 1.21±0.13 (p=0.045).

Conclusions : OCTA can be utilized to qualitatively assess for early signs of radiation retinopathy; however, obtaining reliable images for quantitative analysis can be challenging. Irradiated eyes demonstrated no significant difference in FAZ area, but the acircularity was significantly increased compared to our normative database. Additional imaging and future analysis of intercapillary spacing and vascular density is needed.
¹Weis PMID:26966414
²Gündüz PMID:10326957
³Schneider PMID:22930834
⁴Wilk PMID:27887888
⁵Tam PMID:22039250

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.

 

Fig 1: Averaged 3-frame OCTA image acquired 36 months post-proton beam with parafoveal capillary dropout, scale bar = 500µm.