Serum folate and vitamin B12 levels in patients with bilateral optic neuropathy attending the eye clinic at Muhimbili National Hospital

Abstract

Background Optic neuropathy is a unilateral or bilateral disease of the optic nerve characterized by damage of the optic nerve (cells and sheath) anywhere between the ganglion cell layer and lateral geniculate body. It has different etiologies like ischemia, inflammation, pressure effect, infiltrative, traumatic, nutritional, toxic and hereditary causes. Patients with optic neuropathy usually have visual loss and defective color perception which can affect quality of life. In Tanzania, bilateral optic neuropathy has been reported to be epidemic and the proportion is estimated to be 0.3 to 2.4%. Objective The aim of this study was to determine the serum levels of folate and vitamin B12 in patients with bilateral optic neuropathy attending the eye clinic at Muhimbili National Hospital.

Methodology A cross sectional study was conducted at Muhimbili National Hospital eye clinic in Dar es Salaam from July 2016 to February 2017, where 93 patients with bilateral optic neuropathy were recruited by consecutive sampling method. Patients were examined in the eye clinic and best corrected visual acuity was taken, intraocular pressure was taken and color vision test was done. The anterior segment was examined using a slit lamp biomicroscope. Fundoscopy was examined using slit lamp biomicroscope with 78D and 90 D lenses after full dilation of the pupil. Blood was taken for measurement of folate and vitamin B12serum levels. Data were analyzed using computer software SPSS version 20 and results summarized using frequency tables, and pie charts.

Results Ninety three patients with bilateral optic neuropathy were recruited. There were slightly more males (51.6%) than females and the mean age was 29±3.4years. Low serum levels of folate were found in 60.6% of the patients, while 4.3% of the patients were found to have low serum levels of vitamin B12. About 48.3% of patients had moderate visual impairment of which 66.6% of these patients had low levels of serum folate. The commonest ocular feature was temporal pallor (92.5%) followed by color vision defect (83.9%). Conclusion and Recommendations More than a half of the patients with optic neuropathy had low levels of folate while few had low levels of vitamin B12 and moderate visual impairment was a common feature found in patients studied.

Measurement of serum folate and vitamin B12 levels before initiating treatment for optic neuropathy in order to ascertain the cause of optic neuropathy is proposed.