Glaucoma includes a set of ocular alterations, such a:
- Reduction of the visual field
- Increased intraocular pressure
- Excavation of the optic disc
The first alteration that occurs is an increase in intraocular pressure, which can remain constantly high for a long period of time or alternate with periods in which it also takes normal values. Intraocular pressure is considered pathological when greater than 20-22 mmHg.
Ocular hypertension, in the second stage, is associated as a direct result with damage to the optic disc, which takes on a typical aspect (papilla excavated and pale). Nerve atrophy leads to the third stage, in which there is a decrease in the visual field, initially limited to peripheral vision; this damage coincides with what is felt by the patient as a first symptom (decline in visual acuity), since the most simple form of glaucoma is generally not accompanied by pain in the high ocular pressure phase. Glaucoma is a disease that cannot be solved, although a timely intervention allows stabilizing it with the aid of medical therapy or, in more complicated cases, of surgery. That’s why it is important to follow the ophthalmologist’s instructions, presenting oneself to undergo all checks and performing the required tests, such as the visual field examination.
Glaucoma can be divided into primary and secondary; in the first case, the disease can be traced back to an anatomical-functional alteration of the eye, while in the second case the disease is linked to a pathological event different from the ocular hydrodynamic processes.
As regards primary glaucoma, the most common cause of disease is damage to the trabecular meshwork, which is the area located between the iris and cornea where the aqueous humour is filtered. The altered filtration of the aqueous humour results in an increased intraocular pressure, which in turn causes a compression of the vascular system. Simple glaucoma arises mainly in adulthood, in equal proportion between female and male sex. It occurs in both eyes, although in some cases not simultaneously; it is a disease with hereditary characteristics. Untreated glaucoma can lead to complications such as cataract and, in the elderly, thrombosis of the central retinal vein. It follows, therefore that the prognosis of the disease too varies according to the age of onset. It is important, however, to note that the individual appearance of the signs described above, not present at the same time, does not determine the diagnosis of glaucoma. The correct approach, especially after detecting during a check values of elevated intraocular pressure, would be to perform periodic checks in order to monitor the eye pressure and its possible evolution. The treatment of glaucoma involves the use of medications (eye drops or ointments) with the aim of lowering intraocular pressure. More rarely, subconjunctival injections are performed. In the parasurgical treatment a key role is played by the use of argon laser, which is a photocoagulation treatment that acts on the trabecular meshwork in order to broaden its meshes and consequently facilitate the outflow of the aqueous humour. In the last stage, surgical treatment (trabeculectomy) is taken into account in the event that the previous therapies do not produce any beneficial effects. It is a technique that, by creating a fistula connecting Schlemm’s canal with the trabecular meshwork, allows the outflow of the aqueous humour. The description we have just provided refers to primary glaucoma caused by trabecular block, which is actually the most widespread. Glaucomas caused by alterations to Schlemm’s canal or the angular area are also found less frequently. Secondary glaucomas may instead be caused by generalized inflammations, traumas or alterations of the ocular circulation (secondary glaucoma caused by increased pressure of the episcleral vein is known). A rare type of glaucoma, namely congenital glaucoma, is present since birth and is manifested by very high ocular pressure caused by inherited disorders. The pharmacological and surgical treatments too are different, depending on the type of glaucoma. The drugs used can be, depending on the case, dehydrating agents, drugs with an anti-enzymatic or anti-inflammatory action, or drugs which induce morpho-functional changes in the crystalline lens, in the ciliary body or in the iris. Even the surgical interventions are different, depending on the type of glaucoma on which we must intervene. We can indeed intervene not only on the trabecular meshwork, but also on the iris, the sclera or the vitreous body.
It is useful to inform the patient that a diet low in fat and the elimination of caffeinated drinks, as well as of foods containing monosodium glutamate, are habits which provide an important additional aid to the drug therapy.
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