Pigmented Free-Floating Vitreous Cyst in a Patient with High Myopia and Uveal Coloboma Simulating Choroidal Melanoma

A 60-year-old woman was referred for a pigmented fundus lesion in her right eye that was suspected to be a possible choroidal melanoma. She complained of an intermittent floater in the right eye. Funduscopy revealed peripapillary atrophy and posterior staphyloma due to degenerative myopia, large inferior choroidal coloboma, and a cystic pigmented lesion measuring 7 mm in diameter and 3 mm in thickness located inferiorly when the patient was in the upright position. Following supine positioning, the lesion floated to the macular region. Ultrasonography confirmed that the lesion is cystic and freely mobile. Magnetic resonance imaging showed a well-defined, nodular preretinal intraocular lesion that was hypointense in both T1- and T2-weighted, non-contrast axial images. Observation of the benign vitreous cyst was advised. A free-floating pigmented vitreous cyst can be associated with high myopia and uveal coloboma. Its location in the posterior vitreous can lead to a misdiagnosis of a choroidal melanoma.