A 70-year-old patient presents with progressive deterioration of vision. On examination, the pupillary reaction is sluggish and the lOP is normal. Fundoscopy shows a large and deep cup. Visual field reveals paracentral scotoma. What is the probable diagnosis

Normal Tension Glaucoma An intraocular pressure of less than 21 mm Hg is recorded in about 15% of patients with all the other features of POAG. This condition is labelled as Normal tension glaucoma. Characterstically the angle of anterior chamber is open on gonioscopy and there is no secondary cause for glaucomatous disc changes. NTG is varient of POAG which accounts for 16% of all cases of POAG. Etiopathogenesis : It is believed to result from chronic low vascular perfusion, which makes the optic nerve head susceptible to normal IOP. This view is suppoed by following association which are more common in NTG than in POAG: 1) Raynauld phenomenon i.e., peripheral vascular spasm on cooling. 2) Migraine, 3) Nocturnal systemic hypotension and overeated systemic hypeension. 4)
Reduced blood flow velocity in the ophthalmic aery. Ref:- A K KHURANA; pg num:-224