Vitreous cysts are uncommon ocular findings and may be overlooked in patients with chronic floaters, particularly when symptoms are attributed to vitreous degeneration or posterior vitreous detachment. We report a long-standing free-floating vitreous cyst that masqueraded as vitreous degeneration for two decades.

A 51-year-old woman presented with persistent floaters in her left eye for more than 20 years, which had become increasingly bothersome in recent months. Best-corrected visual acuity was 20/60 in the affected eye. Fundus examination and multimodal imaging revealed a mobile, free-floating pigmented cyst in the vitreous cavity, with a translucent lumen and no attachment to the optic disc or peripheral retina. There were no signs of intraocular inflammation, and serologic testing for parasitic infection was negative. Because of persistent symptoms, pars plana vitrectomy with cyst removal was performed. Histopathologic examination showed a cyst wall lined by pigmented cuboidal epithelial cells, supporting an origin from the pigmented epithelium of the iris or ciliary body. At 2 weeks after surgery, the patient reported symptom relief, and best-corrected visual acuity improved to 20/25.

This case highlights that vitreous cysts can remain symptomatic for many years and may be mistaken for more common causes of floaters. Careful dilated fundus examination, multimodal imaging, and exclusion of inflammatory or parasitic disease are important in establishing the diagnosis. Vitrectomy may be considered in selected symptomatic cases, particularly when complete removal and histopathologic confirmation are desired.

A free-floating vitreous cyst should be considered in patients with long-standing floaters, even when symptoms have previously been attributed to vitreous degeneration. Careful examination can prevent delayed recognition, and surgical removal may provide both symptom relief and diagnostic confirmation.