Clinical meaning
Glaucoma is a group of progressive optic neuropathies characterised by damage to the optic nerve and irreversible vision loss. It is the leading cause of irreversible blindness worldwide. The primary mechanism involves elevated intraocular pressure (IOP) that exceeds the tolerance of retinal ganglion cells, causing axonal damage and cell death at the optic nerve head. Normal IOP ranges from 10 to 21 mmHg and is maintained by a balance between aqueous humour production by the ciliary body and its drainage through the trabecular meshwork into the canal of Schlemm. When drainage is impaired or production exceeds outflow capacity, IOP rises. However, it is important to note that some patients develop glaucomatous damage at statistically normal pressures (normal-tension glaucoma), while others tolerate elevated IOP without damage (ocular hypertension). This means IOP is a major risk factor but not the sole determinant. The two main types are open-angle glaucoma and angle-closure glaucoma. Primary open-angle glaucoma (POAG) is the most common form, accounting for approximately 90% of cases. In POAG, the drainage angle between the iris and cornea appears anatomically open, but microscopic...