Subretinal parasitic lesion mimicking viral retinitis managed with combined medical therapy and laser photocoagulation

Parasitic infections can present with variable manifestations and may mimic viral retinitis, particularly when intraocular inflammation is prominent. We report a case of a 54-year-old woman experiencing worsening blurred vision in her right eye for over a month. She was previously diagnosed with acute retinal necrosis and treated with corticosteroids and acyclovir, but her condition continued to decline. Fundus examination showed dense vitritis and an ill-defined area of retinitis along the superior temporal arcade. Serologic tests were positive for Toxocara IgG and Toxoplasma gondii IgG, while PCR testing of aqueous humor for viral pathogens was negative. Antihelminthic therapy was initiated, resulting in gradual improvement in media clarity and revealing a subretinal parasitic lesion within the area of retinitis. Once confirmed to be extramacular, focal laser photocoagulation was performed. During follow-up, intraocular inflammation subsided, the subretinal parasite fragmented, and best-corrected visual acuity improved to 20/25 and remained stable. This case highlights that parasitic infections should be considered in the differential diagnosis of infectious uveitis that does not respond to initial treatment in regions where parasitic infections are common. Combining focal laser photocoagulation with medical therapy may help control inflammation and preserve vision when a distinct extramacular subretinal parasite is detected. • Subretinal parasite initially mimicked viral retinitis with dense vitritis. • Medical therapy improved visualization of an extramacular subretinal parasite. • Laser photocoagulation was applied to target the subretinal parasite directly. • Combined therapy controlled inflammation and resulted in visual recovery.