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by Dr. Ernesto Pangalangan, Jr.

Primary open angle glaucoma (POAG) is the most common type of glaucoma in some parts of the world. In POAG, the intra-ocular pressure (IOP) is higher than the statistically normal IOP which is about 10-21 mmHg. If the IOP is not lowered, this can result in optic nerve damage which can lead to irreversible blindness.

POAG is a chronic, progressive optic neuropathy characterized by optic nerve head (ONH) and retinal nerve fiber layer (RNFL) changes, usually with corresponding visual field defects. The IOP is usually above 21mmHg and the irido-corneal angles are open on gonioscopy. It usually appears spontaneously and may be an incidental finding in a routine eye exam without any antecedent or related disease and has no known basis other than genetic or familial predisposition. It is usually asymptomatic until late in the disease where decreased peripheral and central vision may be noted. While typically bilateral, it can be asymmetric.

Risk factors for POAG are the following: elevated IOP (greater than 21 mmHg), positive family history, older age, race, myopia (higher than 4 diopters) and those with vascular factors like cardiovascular disease, systemic hyper/hypotension, vasospastic phenomena and diabetes mellitus. An optic disc finding of a disc hemorrhage could mean progression of the disease.

Early detection is of utmost importance. Diagnostic evaluation includes a careful history, slit-lamp examination, IOP measurement, gonioscopy (examination of the fluid drain of the eye) and perimetry (testing of the field of vision). Newer modalities like the quantitative optic disc and retinal nerve fiber layer imaging (OCT, HRT) or selective perimetry (FDT, SWAP) may also be done.

Mainstay of therapy of this disease is lowering of IOP. Depending on the stage, medication (eyedrops), laser, or incisional surgery can be used to control the IOP. Since there is no cure for glaucoma, lifelong monitoring is needed.