Normal Pressure Glaucoma (Low Tension Glaucoma)
Normal pressure glaucoma or normal tension glaucoma or low tension glaucoma is a type of chronic open angle glaucoma in which there is normal intraocular pressure or even low intraocular pressure and that is way it is called sometimes as low tension glaucoma.There is progressive optic nerve damage with visual field defects similar to those occurs in glaucoma nerve damage.
As in Primary Open Angle Glaucoma, this type is painless and the angle is opened with gonioscopic examination. There is glaucomatous optic disc cupping and visual field defects due to nerve fiber layer loss.
Risk Factors of Normal Pressure Glaucoma
1- Age: Old age.
2- Race: More in Japanese.
3- Gender: Female are at greater risk.
4- Family history: Occur more with positive family history.
5- Systemic association: Local vascular factors play a significant role in the development of this disorder in which most of the patients with this disorder have vascular disorders like hypertension, atherosclerosis, migraine headache, ischemic vascular diseases, autoimmune vascular diseases, coagulopathies diseases and peripheral vasospasm like in Raynaud's phenomenon.
The reasons behind it are unknown but some experts believe that low blood pressure with decrease blood flow to optic nerve plays a major rule in it.
It will be always helpful to check blood pressure especially nocturnal blood pressure as some experts believe that optic nerve damage occur mainly through night, where blood pressure decrease more.
On those people intra-ocular pressure should be lower than normal to prevent further damage because in those patients, optic nerve cells are more sensitive to pressure-related damage than others.
Normal tension glaucoma visual field defect
Visual Field is very important diagnostic tool. It shows defects that are steeper, deeper and closer to fixation than in patients with Primary Open Angle Glaucoma. Visual Field defects are larger than that appear in optic disc appearance.
Treatment of Normal Pressure Glaucoma
1- As with primary Open Angle Glaucoma, we should start with medical treatments with follow up visits to make sure that treatment is adequate by ordering visual field test and by OCT, to make sure that there is no progressive damage despite low Intraocular Pressure.
2- In case the medical treatment failed, we can consider surgery like trabeculectomy.
3- Treatment of the systemic conditions and monitoring of the blood pressure to prevent the occurrence of nocturnal drop in blood pressure.
In case of inadequate results, we can use either laser treatment or glaucoma filtering surgery. Read more about surgical procedures for glaucoma.