Normal tension glaucoma

EN Texto en inglés Aún no hay artículo en tu idioma: extracto en inglés.

Normal tension glaucoma (NTG) is an eye disease, a neuropathy of the optic nerve, that shows all the characteristics of primary open angle glaucoma except one: the elevated intraocular pressure (IOP) - the classic hallmark of glaucoma - is missing. Normal tension glaucoma is in many cases closely associated with general issues of blood circulation and of organ perfusion like arterial hypotension, metabolic syndrome, and Flammer syndrome. Over many years, glaucoma has been defined by an intraocular pressure of more than 20 mm Hg. Incompatible with this (now obsolete) definition of glaucoma was the ever larger number of cases that have been reported in medical literature in the 1980s and 1990s who had the typical signs of glaucomatous damage, like optic nerve head excavation and thinning of the retinal nerve fiber layer, while these patients had an IOP that would generally have been regarded as "normal". It is now widely estimated that a larger percentage of patients with primary open-angle glaucoma (POAG) are suffering from normal tension glaucoma. Among Americans of Japanese descent, for instance, the prevalence of NTG is about four times as high as the prevalence of the "classical glaucoma" with an IOP of 22 mm Hg and higher. The pillar of the current understanding of normal tension glaucoma is a reduced IOP tolerance of the retinal ganglion cells and the cells in the optic nerve head - an IOP of, for example, 17 or 19 mm Hg that would not affect a healthy eye leads to damage in the eye of an NTG patient. In many patients, normal tension glaucoma is common in individuals with a generalized reduced perfusion of organs and certain body tissues. A low blood pressure - whether consistently low or with sudden pressure drops - is associated with NTG as are conditions like Flammer syndrome and obstructive sleep apnea. Flammer syndrome has been attributed to increase the likelihood of ganglion cell damage in normal tension glaucoma patients with disc hemorrhages as a characteristic clinical sign.