Facts of cases are unclear

Editor—In the report by Schönhöfer et al of visual loss related to the proton pump inhibitor omeprazole, several issues need clarification.1 Six of the nine cases are stated to have had “funduscopically confirmed” irreversible anterior ischaemic optic neuropathy. This clinical entity is not diagnosed solely on the basis of fundal findings but in the light of the nature and pattern of visual loss, the appearances of the optic disc in both eyes—an important clue being a relatively small optic disc in the unaffected eye2—and the results of fluorescein angiography. This is an important consideration because many forms of anterior optic neuropathy, including demyelinative or postviral optic neuritis and neoplastic optic nerve inflitration, can produce the same appearance of the optic nerve head as anterior ischaemic optic neuropathy. Indeed, the authors seem to be unclear whether demyelinative optic neuritis or anterior ischaemic optic neuropathy is associated with multiple sclerosis.

It is also stated that two patients had no known risk factors for anterior ischaemic optic neuropathy. In fact, both had gastrointestinal ulcers, which have been shown in a prospective review of over 400 patients to be significantly associated with non-arteritic anterior ischaemic optic neuropathy.3 This in itself generates difficulty when attempting to associate a treatment for gastrointestinal ulcers with an increased risk of anterior ischaemic optic neuropathy.

In their concluding sentence, the authors say that anterior ischaemic optic neuropathy is due to retinal artery ischaemia, whereas it is due to a perfusion deficit in the posterior ciliary circulation. There may well be an association between omeprazole and optic nerve dysfunction, but this paper fails to provide conclusive evidence of such an association or a clear understanding of its possible aetiology.

Concerns on safety of drug are unwarranted

Editor—Schönhöfer et al's article on …