OCT and OCTA Features of Optic Disc Melanocytoma: PHOMS, Perfusion Deficits, and Association with Vision Loss.

Purpose: To investigate the structural and vascular alternations of optic disc melanocytoma (ODM) using optical coherence tomography (OCT) and OCT angiography (OCTA) DESIGN: Retrospective case-series study.

Subjects: This study included 34 eyes diagnosed with ODM and 15 eyes with juxtapapillary choroidal melanoma (CM) who referred to Beijing Tongren Hospital from July 2019 to March 2025.

Methods: All subjects underwent OCT and OCTA cover the macula and optic nerve head (ONH) region.

Main Outcome Measures: The presence of peripapillary hyperreflective ovoid mass-like structures (PHOMS), and ONH vessel density were quantitatively analyzed and correlated with clinical parameters.

Results: ODM was characterized as a hyper-reflectivity anterior surface and dense posterior optic shadowing. PHOMS were observed in the 30 cases of ODM (88.2%), significantly more frequent than in fellow eyes (17.1%, P<0.001). Epiretinal membrane was present in 20.6% of ODM cases, compared to fellow eyes (2.94%, P=0.054). OCTA revealed reduced ONH vessel density in ODM eyes, predominately affecting the radial peripapillary capillary (RPC) layer on the tumor surface, which resulted in 14 cases of localized RPC atrophy and patchy non-perfusion areas on En-face images. Eyes with non-perfusion areas demonstrated worse visual acuity (LogMAR: 0.29 ± 0.36 vs. 0.93 ± 1.29, P =0.06), larger tumor basal diameter (3.9 vs. 2.6mm, P=0.05), and tumor thickness (1.6 vs. 1.1mm, P=0.03). No intrinsic tumor vasculature was identified within ODM, contrasting with the disorganized vascular network seen in all 15 cases of juxtapapillary CM.

Conclusions: ODM is associated with significant structural and vascular alterations, including PHOMS, ONH hypoperfusion, and eventually RNFL atrophy. These features reflect both mechanical compression and ischemic injury to the optic nerve and can be used to assess visual prognosis. The absence of intrinsic tumor vasculature in ODM underscores its fundamental difference in biological behavior from juxtapapillary CM.