Comparison of between Primary Open Angle glaucoma (POAG) and Ocular Hypertension (OHT) with special reference to mean Central Corneal Thickness (CCT)

Glaucoma affects more than 67 million persons worldwide, of whom about 10%, or 6.6 million, are estimated to be blind1 . Glaucoma is the leading cause of irreversible blindness worldwide and is second only to cataract as the most common cause of blindness overall1 . 

In India, the estimated number of cases of glaucoma is 12 million, around one fifth of the global burden of glaucoma. 2 Glaucoma is an optic neuropathy with the characteristic appearance of an optic disc and a specific pattern of visual field defects, that is associated frequently but not invariably with a raised IOP.3 

The term ocular hypertension was advocated in the 1970s to distinguish persons with ‘normal’ intraocular pressure (IOP) (i.e., =21 mm Hg) from those with an IOP greater than 21 mm Hg, who were considered to be at increased risk for open angle glaucoma4,5 

Intraocular pressure (IOP) - The normal IOP can be defined as that pressure which is compatible with normal health and function of the eye. It is that pressure, which if maintained does not lead to glaucomatous damage of the optic nerve head. Elevated intraocular pressure (IOP) is a positive risk factor for the development of glaucomatous optic nerve damage and visual field loss. 6 Goldmann Applanation Tonometry (GAT) has been considered to be the gold standard for determining the IOP. 

Glaucoma is diagnosed with presence of either optic nerve changes or visual field changes along with increase IOP. When IOP is raised without any visual field changes and optic nerve changes then it is Ocular Hypertension. 

Open-angle glaucoma (OAG) is the most common type of glaucoma. In open-angle glaucoma, slow damage to the nerve in the back of the eye (optic nerve) causes gradual loss of eyesight.