Are intracranial pressure fluctuations important in glaucoma?

Glaucoma is one of the leading causes of irreversible blindness. Primary open-angle glaucoma (POAG), the most common type, is a progressive optic neuropathy with characteristic structural changes in the optic nerve head and functional changes in the visual field. Mechanical and vascular theories for the pathogenesis of glaucomatous optic neuropathy have been proposed. Elevated intraocular pressure (IOP) is a strong risk factor, although a subset of POAG patients has normal IOP and is designated normal tension glaucoma (NTG). Clearly, factors other than IOP are likely to be involved in retinal ganglion cell death in glaucoma. An intriguing finding of recent studies is that intracranial pressure (ICP) is lower in patients with POAG and NTG when compared with nonglaucomatous control subjects. It has been suggested that the relationship between IOP and ICP may play a fundamental role in the development of glaucoma. A decreased ICP could result in an increased trans-lamina cribrosa pressure difference (IOP minus ICP) and lead to glaucomatous damage. In the present paper, we raise the question of whether ICP fluctuations also may be important in glaucoma. The effect of ICP fluctuation might be comparable to that of IOP fluctuation, which has been recognized as an independent risk factor for glaucoma progression.