Editor,—We read with interest the paper recently published by Kawasaki et al.1They suggested that hyperhomocysteinaemia may have a role in the occurrence of non-arteritic anterior ischaemic optic neuropathy (NAION) in non-diabetic patients younger than 50 years, and raised the question of the frequency of the methylene tetrahydrofolate reductase (MTHFR) C677T mutation in this population.

There have been anecdotal reports of thrombotic tendencies in patients with NAION.2-4 Although NAION is most probably related to local factors compromising the posterior ciliary artery circulation at the optic nerve head (so called “disc at risk”), it is also possible that some systemic factors such as hyperhomocysteinaemia and the MTHFR C677T mutation may enhance local atherogenesis at the level of the posterior ciliary arteries, thereby precipitating the development of NAION in those at risk for …