In the news: Restoring B12 Sufficiency Eases Neuropathic Pain in Dry Eye

Vitamin B12 & Neuropathic Ocular Pain

Dry eye disease (DED) associated ocular pain is considered chronic when it persists for more than 6 months. In chronic ocular pain, changes can occur in the ocular sensory apparatus and eventually in the central nervous system. Chronic inflammation and nerve damage can lead to abnormal activation of the eye’s sensory fibers and result in neuropathic pain.

Ocular pain may result from various diseases that lead to progressive corneal nerve damage. Deficiency of vitamin B12, essential for normal neurosensory functioning, may be a contributing factor. It has been associated with pain disorders such as myofascial pain, and it’s experimentally shown to improve corneal reinnervation.

University researchers in Turkey observed that some dry eye patients in their clinical practice continued to suffer from chronic ocular pain after local anesthetic instillation and treatment with cyclosporine and artificial tears. It was determined that a subset of patients were B12 deficient, leading the researchers to investigate the effect of vitamin B12 deficiency and therapy on ocular pain and symptoms in DED (1).

Design and Methods

Ninety patients with severe DED were enrolled and followed for 12 weeks. Those with overt B12 deficiency (n= 45) received parental vitamin B12 (1000 mcg/ml intramuscular injection) along with topical treatment (artificial tears and cyclosporine); those with normal B12 serum levels received only topical treatment. OSDI score, OSDI 3rd question score (to determine pain and pain frequency), TBUT, and Schirmer’s test were evaluated at baseline and at 12 weeks.

Results

All four evaluation measures improved in both groups (p<0.001 for each measure, all groups). Mean vitamin B12 levels improved in the vitamin deficient group from 144 pg/ml at baseline to 450 pg/ml at study’s end, similar to the baseline values in the B12 sufficient group (417.5 pg/ml). While mean score changes between groups was not statistically significant, the OSDI score and 3rd OSDI question score decreased markedly in the B12 deficient group (-30.8 and -2.82 respectively, both p<0.001). TBUT and Schirmer’s values rose significantly in the B12 deficient group (+7.98 and +12.16 mm, respectively), as well as in the B12 sufficient group (+6.18 and +6.71, respectively). The improvement in both evaluation measures was better in the group with poor B12 status. Conclusion Neuropathic pain is more likely to be chronic, difficult to treat, and thus important to distinguish in dry eye patients. “Serum vitamin B12 levels should be measured and taken into account for managing symptoms and neuropathic pain in DED patients who continue to have dry eye symptoms while on current therapies,” according to the authors.

Comments

While vitamin B12 deficiency alone does not cause ocular surface disease, it may aggravate pathologic changes and neurosensory damage to corneal nerves, resulting in neuropathic pain.

Marginal to deficient status of this vitamin may be more widespread than previously thought, particularly in older individuals, vegans, some vegetarians, and during pregnancy. While the overall prevalence of vitamin B12 deficiency is unknown, the Framingham Offspring Study found up to 39% of US adults at risk for vitamin B12 deficiency (defined as serum vitamin B12 <258 picomols/L; <350 picograms/mL).  

It’s important to note that, though vitamin B12 was given parenterally in this study, high dose oral B12 supplements are proven to work as well as injections in correcting deficiency and at a lower cost (2).

References

1. Ozen S, et al. Vitamin B12 deficiency evaluation and treatment in severe dry eye disease with neuropathic ocular pain. Graefes Arch Clin Exp Ophthalmol. Epub March, 2017.
2. Lin J, et al. Is high-dose oral B12 a safe and effective alternative to a B12 injection? J Fam Prac. 61:162-3, 2012.