The elusive nature of primary intraocular lymphoma.

A 58-year-old woman with an initial diagnosis of multiple evanescent white dot syndrome OU experienced deteriorating vision despite corticosteroid treatment. Reevaluation disclosed retinal and subretinal infiltrates and pigmentary alterations, prompting a suspicion of primary intraocular lymphoma (PIOL). Diagnostic vitrectomy yielded inconclusive cytology, but flow cytometry demonstrated small monoclonal B cells less suggestive of PIOL than of small lymphocytic lymphoma originating outside the eye or central nervous system. Brain magnetic resonance imaging, chest/abdomen/pelvis computed tomography, lumbar puncture, and laboratory studies failed to disclose lymphoma elsewhere. There was insufficient evidence to recommend radiation therapy. Vision deteriorated rapidly, prompting a diagnostic retinal biopsy and aspiration of the subretinal infiltrate, revealing unequivocal evidence of PIOL. After 40 Gy orbital x-irradiation, visual function improved dramatically. This case emphasizes the unusual ocular manifestations of PIOL and the difficulty of obtaining a definitive diagnosis by sampling vitreous, particularly after corticosteroid treatment. In such cases, subretinal aspiration or retinal biopsy may be necessary. Timely diagnosis is critical because treatment can reverse visual loss if it is not severe.