Longitudinal Optical Coherence Tomographic follow-up of a 10-year-old girl with unilateral retinal parasitism.

Objective: Retinal parasitism by worms is a rare clinical occurrence and may cause diagnostic and therapeutic challenges. We present a girl with unilateral involvement who was first diagnosed at the age of 10. Change in parasite appearance inside the lesion was recorded by optical coherence tomography (OCT) 14 years apart.

Methods: Case report.

Results: A 10-year-old girl was referred to our clinic with a presumptive diagnosis of a unilateral posterior pole mass. She had been examined at another institution for the left exotropia and decreased vision, without any accompanying systemic symptoms. Upon our examination, a subretinal lesion, of two disc diameters in size, was detected two disc diameters above the left optic disc, and a spiral-shaped, non-motile roundworm could be spotted inside the lesion. Adjacent chorioretinal atrophy and marked fibrosis surrounded the lesion, without any active inflammation. OCT sections through the lesion delineated the hyperreflective appearance of the spiraling roundworm. Fourteen years later, the worm inside the lesion had lost its spiraling form, and the remnants appeared as a coalesced whitish material inside the lesion on the OCT.

Discussion: Although rare, retinal parasitism by worms presents significant diagnostic challenges due to its atypical presentation and the potential for misdiagnosis. In this case, the initial presentation of a subretinal lesion containing a spiral-shaped roundworm was notable for its lack of associated systemic symptoms and the absence of active inflammation, often seen in more common ocular infections. The long-term follow-up, using OCT, provided valuable insights into the infection's natural course, showing the gradual degeneration and transformation of the parasite into a coalesced whitish material, over 14 years. This case underlines the importance of longitudinal imaging in understanding the progression of such unusual retinal conditions and the need for awareness of parasitic infections as a differential diagnosis in similar clinical scenarios.

Conclusions: The present case demonstrates the natural evolution of the inactive subretinal worm by OCT and color fundus images.