The College of Optometrists

in normal tension glaucoma what is actually causing the damage to the disc, and is glaucoma always the result of some form of blockage at the meshowrk?

NTG is still not fully understood, but there is thought to be a vascular component ie. poor vascular perfusion of the optic nerve makes it more succeptible to damage, even at "normal" IOP. These patients often have a history of migraine, or raynauds disease, which are both related to lack of vascular perfusion.

Not quite sure what you mean by your second question - most glaucoma in this country is primary open angle, so the trabecular meshwork is open and not blocked.

welll i think its associated with systemic hypotension. At night time while Px is asleep, there is poor vascualr supply to the optic nerve leading to most damage at that point

Elevated IOP in glaucoma is the result of under drainage of AqH rather than over production, whether this is due to blockage of the TM is not known for POAG Pxs.

Also ophthalmologists will be very keen on phasing IOP to make sure the "NTG" patients arent getting spikes in IOP,which often is the case.

IOP also goes up if there is problem with uveo-scleral drainage which can result from a problem along the venous drainage away from the globe.