| الوصف: |
Glaucoma is a degenerative and progressive pathology involving the optic nerve with consequent loss of the visual field: it is a particularly severe ocular affection constituting the second cause of blindness in the world. This disease may occur at any age even though it is more frequently found in senior people (Quigley, 1987; Morgan, 2000). Five different types of the disease have been described: two of them are defined as primary open angle or, alternatively, closed angle, which is possibly the most common one (Joseph & Grienson, 1994). Retinal gangliar cells were reported to be the ones mainly damaged by the disease as shown in classical studies by Quigley (Quigley et al., 1998). The disease causes a reduction of the axons forming the optic nerve (Capaccioli et al., 1998). The etiology of glaucoma may be due to two different types of damage: either mechanical or ischemic. In any case, it is commonly accepted that an increased intraocular pressure represents a major risk factor in the development of the disease, and actually, it may be one of the principal causes (Quigley et al., 1994; De Gregorio et al., 1997; Sommers et al., 1991; Friedman et al., 2004). Under the clinical point of view, the increase of pressure is apparently attributable to the alteration of the ocular hydrodynamics, which determines a normal efflux of the aqueous humor from the anterior chamber. Different types of glaucoma exist in particular, in the case of the open angle glaucoma, the lack of efflux depends particularly on obstructions in the trabecular network, while the primary closed angle glaucoma involves a modification the irido-corneal angle. Other ocular pathologies exist where the vitreous efflux is altered but, in these cases, the pathology is defined as secondary glaucoma: also in this pathological condition, the open and the closed angle have been described. In any case, the elevated intraocular pressure seems to be the most relevant pathogenic phenomenon determining the neuropathy although it may be not the only one (Quigley et al., 1994; De Gregorio et al., 1997; Sommers et al., 1991). With respect to this, the synergic action of other factors seems to be proved by the existence of glaucomatous pathologies occurring in conditions of normal ocular pressure: however, a reduced retinal and optic nerve perfusion could play a role due to a deficient blood delivery to these ocular structures. The immunological aspect of the disease should be also considered: for instance in glaucoma patients several auto-immuno |
