Managing Normal Tension Glaucoma with Dietary Folate

Abstract

Normal-Tension Glaucoma (NTG) is the most prevalent form of glaucoma among individuals in Asian countries. While lowering intraocular pressure (IOP) remains the standard of care, this approach is insufficient for most NTG patients. Recent evidence documents the role of ischemia and oxidative stress as critical factors affecting the optic nerve in NTG. Consequently, addressing these factors has been recommended as a neuroprotective strategy. While conventional treatment strategies primarily target the reduction of IOP, this yields limited efficacy and eventual blindness in many NTG cases. Recent studies document another crucial parameter: Retinal Venous Pressure (RVP). Elevated RVP impedes retinal perfusion, resulting in oxidative stress and localized ischemia, and exacerbating optic nerve damage in NTG. Elevated RVP also appears to be a contributing factor in small vessel ischemia associated with diabetic retinopathy and macular degeneration. The underlying cause of elevated RVP is small vessel endotheliopathy, which may result from alterations in methylation and B-vitamin metabolism, leading to changed microcirculation. This metabolic disruption can arise from dietary inadequacies, malabsorption, or genetic polymorphisms affecting the methylation pathways. Restoring plasma levels of folate and B-12 can be achieved through supplementation with natural forms of these vitamins, specifically L-methylfolate, and methylcobalamin. Unlike oxidized folate (folic acid), which must be enzymatically converted to methylfolate to penetrate the blood-retinal barrier, L-methylfolate can be directly utilized. Excess unmetabolized folic acid can impede methyl folate absorption into the retina, underscoring the necessity of using methyl folate for effective supplementation. We propose integrating RVP screening into NTG risk assessments and consider a targeted vitamin supplement, such as Ocufolin®, as a viable adjunct approach to manage elevated RVP and potentially mitigate NTG progression.