OCT Angiography Analysis of Retinal and Choroidal Flow after Proton Beam Therapy for Choroidal Melanoma

Abstract

Purpose: To evaluate the macular and peripapillary retinal and choroidal flow changes in eyes with choroidal melanoma (CM) treated with proton beam radiation therapy (PBRT) using OCT angiography (OCTA).

Design: A prospective, cross-sectional, single-center study.

Participants: All patients seen at the study center between 2019 and 2024 who received PBRT for CM in 1 eye ≥1 year before enrollment with best-corrected visual acuity (BCVA) >20/200, unremarkable contralateral eye, and agreed to participate.

Methods: After a comprehensive eye examination, including BCVA, Optovue AngioVue was used to obtain the 4.5-mm optic disc and 6.0-mm macular OCT/OCT angiography (OCTA) images of both eyes. All vascular density (VD) measurements were obtained automatically using the OCTA software, except choriocapillaris VD, which was quantitated using ImageJ. The Wilcoxon signed-rank test was used to analyze differences in OCT/OCTA parameters between the treated and the contralateral eyes. Spearman's ρ was used to identify OCTA parameters associated with BCVA or radiation dose. A P value of <0.05 was considered statistically significant.

Main outcome measures: Foveal avascular zone (FAZ) area and perimeter, choriocapillaris and retinal (superficial and deep) capillary VD in the macula and radial peripapillary capillary (RPC) VD on OCTA; macular and retinal nerve fiber layer thickness on OCT, tumor location, laterality and size at baseline, BCVA of both eyes, PBRT dose, and duration of follow-up at enrollment.

Results: Among 24 participants, OCT/OCTA parameters were significantly different in the treated eyes when compared with the contralateral eyes, including increased FAZ area and perimeter, decreased peripapillary retinal nerve fiber layer thickness and RPC VD, and decreased macular choriocapillaris VD and parafoveal and perifoveal superficial retinal plexus VD (P < 0.05). Best-corrected visual acuity in the treated eyes correlated significantly with FAZ area and perimeter, parafoveal and perifoveal deep retinal plexus VD, and radiation dose to fovea but not radiation dose to the optic disc.

Conclusions: Although PBRT can affect both retinal and choroidal vascular flow in the macular and peripapillary region in eyes with CM, BCVA after PBRT seems to correlate best with the retinal vascular flow changes in the macula on OCTA and radiation dose to the fovea.

Financial disclosures: Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Keywords: Choroid; Foveal avascular zone; Macula; Radiation; Uveal melanoma.

Figure 1

Representative en face macular OCT angiography (OCTA) image of the choriocapillaris showing conversion of the grayscale image into a black/white image for quantitation with ImageJ program using the Phansalkar algorithm. A 6 × 6 mm OCTA image of the choriocapillaris layer of the eye treated with PBRT for choroidal melanoma before (A) and after (B) Phansalkar auto local thresholding. Flow voids are represented by the darker spaces. Note the relatively higher density of flow voids around the fovea in this eye.

Figure 2

Representative fundus images and macular OCT and OCT angiography (OCTA) images of 2 study eyes with choroidal melanoma after treatment with proton beam radiation therapy (PBRT). A, Top shows ultrawide field scanning laser ophthalmoscopy (SLO) fundus image showing a choroidal melanoma just superior to the disc in the left eye of a 71-year-old woman with BCVA 20/20 at 22 months after PBRT. The macular OCT (second row) of this eye is unremarkable. The macular OCTA image (third and fourth rows) of the superficial and deep capillary plexus shows only minimal flow abnormalities. B, Ultrawide SLO fundus image (top) the left eye of a 70-year-old man with a peripapillary choroidal melanoma involving the inferior macula with BCVA 20/200 at 20 months after PBRT. The macular OCT image of this eye (second row) shows diffuse cystoid macular edema persisting despite monthly anti-VEGF therapy. Corresponding macular OCTA images of the superficial plexus (third row), deep plexus (fourth row), and choriocapillaris (fifth row) show flow voids, especially in the inferior macula where the tumor is located.