![]() Vision loss in patients with OAG can be a severe and chronic, or insidious process. The exact biological basis of glaucoma and its contributing factors are yet to be conclusively established however, as the disease is multi-factorial, chronic and progressive, it is believed that both environmental and genetic causes play key roles in its development. ONL: Outer nuclear layer, OPL: Outer plexiform layer, INL: Inner nuclear layer, IPL: Inner plexiform layer, GCL: Ganglion cell layer The schematics of sensory (visual) input into the bran showing RGCs receiving visual information from photoreceptors via bi-polar and retina amacrine cells to collectively transmit image forming and non-image forming visual information via the visual pathway to the brain (copyright licensed provided). As RGCs cannot regenerate independently, degeneration of neurons surrounding RGCs followed by RGC apoptosis generally results in reduced visual acuity and/or permanent visual loss. It has been decisively established that degeneration of optic nerve head (ONH) plays an important role in initial axonal damage in the onset of glaucoma. Clinically, glaucoma is the result of RGC axonal degeneration and characteristic optic nerve head cupping. RGCs receive visual information from photoreceptors via bipolar and retina amacrine cells to collectively transmit image-forming and non-image forming visual information via the visual pathway to the brain, as shown in Fig. Ischemic optic neuropathy, is identified by the growing degeneration of RGC through oxidative damage, uncontrolled immune activity and/or dysfunction of glial cells. Primary and secondary OAGs and ACGs can be further characterised based on their inciting factors using two theories of development, mechanical and ischemic. OAG accounts for the majority of glaucoma cases (approximately 80% in the United States) although, ACG is also responsible for a significant number of patients with blindness. OAG and ACG can be further sub-divided into primary and secondary glaucomas primary glaucoma develops due to an unknown cause, whereas secondary glaucoma develops from a known cause such as an eye injury, cataract, tumour, or diabetes. This disease is broadly sub-divided into open-angle glaucoma (OAG) and angle-closure glaucoma (ACG), also known as acute or narrow-angle glaucoma the division is based on the status of the internal drainage and the anatomy of the anterior chamber, both of which result in characteristic optic nerve degeneration in the posterior eye. Due to the fact that an in-depth discussion and analysis of the pathogenesis of glaucoma is beyond the scope of this study, a summary of the glaucoma: clinical types, risk factors, pathogenesis, and diagnosis are outlined in the sections below. ![]()
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