Normal-Tension Glaucoma: Can I Have Glaucoma With Normal Eye Pressure?

A person can develop glaucoma even with normal eye pressure that is between 12 and 21 millimeters of mercury! Usually, in most cases of glaucoma, the intraocular pressure builds up as a result of a malfunctioning of the aqueous humour drainage system at the level of Trabecular meshwork. The system blocks aqueous humour drainage when the patient has open-angle glaucoma, pressure builds up to levels above 21mmHg, and the optic nerve progressively suffers and becomes damaged.

Glaucoma can also occur when the eye pressure is normal or lower. In this case, it is called Normal-tension glaucoma (NTG) or Low-tension glaucoma (LTG) if the eye pressure is below normal. A 2008 Research revealed that NTG is more common than was previously perceived. Population-based studies have found that the prevalence of NTG is anywhere from 10% to 48% of all open-angle glaucoma patients in the United States, Europe, and Scandinavia. Up to 66% of patients in the Japanese have NTG. NTG appears to be more common in myopic patients, among women, patients with systemic hypotension due to both postural and nocturnal, as well as among patients with migraines and other vasospastic disorders.

LTG and NTG are conditions where patients represent glaucoma-like field defects, optic nerve head cupping, and normal intraocular pressures. Experts agree that genetics, vascular abnormalities, and intracranial pressure play a major role in the pathogenesis of LTG and NTG. Other risk factors include vasospastic systemic conditions such as the Raynaud phenomenon and migraine, ischemic vascular disease, and increased diastolic blood pressure.

The probability of blindness in patients with NTG is much lower than in patients with high-tension glaucoma. Nevertheless, NTG patients should be followed with care, especially those with reduced best-corrected visual acuity and diagnosed visual field loss.