Ocular neuropathic pain linked to vitamin B12 deficiency

This case report brings to light a potentially under-diagnosed cause of ocular neuropathic pain – vitamin B12 deficiency.

A 28-year-old Indian man who had uneventful LASIK 5 years earlier develops severe burning pain, irritation and foreign body sensation in both eyes during the previous year. Ocular exams showed some bilateral punctate epithelial erosions and a rapid tear breakup time, but was otherwise unremarkable. Treatment with preservative-free artificial tears and 0.05% topical cyclosporine failed to alleviate symptoms.

Blood tests showed low levels of serum vitamin B12 at 90 pg/mL (reference range, 236-944 pg/mL). The patient was prescribed 1000μg intramuscular daily for 1 week followed by 1000μg monthly oral supplements for 6 months, in addition to topical therapy. Within 3 weeks, the patient’s symptoms were completely relieved and all ocular surface disease parameters improved. At last follow-up, the patient was symptom-free and stopped using all topical medication.

Patients with ocular neuropathic pain often experience symptoms out-of-proportion to findings and often do not respond to topical therapy. In the United States, vitamin B12 deficiency may be observed in patients with pernicious anemia, prior bariatric surgery, celiac disease or Crohn’s disease and immune system disorders including Graves’ disease and lupus. It may also occur in vegans or vegetarians who are not consuming enough eggs or dairy products.

As a result, it is important to take a detailed history, including dietary history, when evaluating patients with more challenging ocular surface issues. The authors conclude that vitamin B12 deficiency should be considered in the differential diagnosis of ocular neuropathic pain and dry eye in patients presenting with recalcitrant ocular neuropathic pain.