Unilateral Blurred Vision as the Sole Presenting Symptom of Chronic Lymphocytic Leukemia

PURPOSE: To describe a case of infiltrative optic neuropathy caused by chronic lymphocytic leukemia. CASE REPORT: A 41-year-old white male presented with painless, blurry vision in the left eye. Examination revealed unilateral optic nerve swelling confirmed by optical coherence tomography (OCT). Initial workup revealed mild leukocytosis, eventually diagnosed as chronic lymphocytic leukemia (CLL). No other cause of optic neuropathy was identified despite extensive investigation. The patient developed rapidly progressive retinal ganglion cell nerve fiber layer (NFL) atrophy and relative afferent pupillary defect (RAPD) of the left eye despite steroid treatment but stabilized after four cycles of CLL-targeted chemotherapy. Although infiltrative optic neuropathy is well-known in leukemia, presentation with only subtle vision loss is rare. Vision loss usually presents late in leukemic infiltrative optic neuropathy and therefore must be considered in patients with optic disc swelling and leukocytosis. CONCLUSION: When treating CLL, progressive visual decline with coexistent optic neuropathy may warrant chemotherapy.