Histological changes It is estimated that roughly 20 to 50% of the large retinal ganglion cells (RGC) are lost in POAG. Although the reduction of RGC density occurs equally throughout the retina, visual sensitivity is first lost in areas where the initial RGC density is low, especially in the peripheral regions of the retina. As the disease progresses, atrophy of the nerve fiber layer is usually observed as additional RGC is lost. Typically, vertical collapse of the optic nerve head (ONH), loss of the neural rim at the ONH, rearrangement of central blood vessels, and loss of supporting tissue occur. Scanning electron microscopy of retinas with early stages of glaucoma shows evidence of initial collapse of the anterior lamina cribrosa, primarily in the vertical poles of the optic nerve head. Based on primate studies, optic cups with larger diameters are more susceptible to high ocular pressure and thus to glaucoma.
Role of the trabecular meshwork Trabecular meshwork (TM) is a lamellated sheet of complex tissue that covers the inner wall of Schlemm's canal. TM has uniquely developed at the angle of primates, filtering the aqueous humor out of the eye. TM consists of two parts: the nonfiltering portion mainly occupied by trabecular cells and the filtering portion. Trabecular cells are highly phagocytic cells removing particles, cell debris, and protein from the aqueous humor. The first glaucoma locus, the trabecular meshwork inducible glucocorticoid response (TIGR), also known as myocilin, initially was identified by looking at genes whose transcription is highly induced by steroids in these cells. The filtering portion consists of three tissues: the cribriform layer, the corneoscleral meshwork, and the uveal meshwork. These trabecular beams or strands are intertwiningly connected to each other, forming a complex filtering mesh surrounding Schlemm's canal. The trabecular beams are thickened by accumulation of extracellular materials and decrease of cell density within the corneoscleral and uveal mesh-work in aged eyes.
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Your heart pumps blood throughout your body using a network of tubing called arteries and capillaries which return the blood back to your heart via your veins. Blood pressure is the force of the blood pushing against the walls of your arteries as your heart beats.Learn more...