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Glaucoma

Definition

Glaucoma is a relatively frequent eye disease characterized by an increase in fluid pressure inside the eye. This increase in fluid pressure is due to an obstruction of the trabeculum filter, which facilitates the evacuation of intraocular fluid. Progressively, this excess pressure damages the delicate fibres of the optic nerve, causing slow deterioration of the field of vision and eventual blindness1.

According to the origins of the increase in intraocular pressure (IOP), various kinds of glaucoma are defined, including the primary glaucoma, of particular interest, and the secondary glaucoma.

The primary glaucoma, divided into 2 categories:

  • On the one hand, primary angle-closure glaucoma, resulting from a blockage of the aqueous humor draining, this leads to a significant increase in IOP. Among them, there are mainly:
    • Acute glaucoma, due to papillary blocking, which prevents the aqueous humor pupillary transit when the iris and the crystalline lens are coming closer together, or to the plateau iris syndrome, an abnormal morphology of the iris which prevents the evacuation of aqueous humor.
    • Subacute glaucoma,a moderate acute glaucoma which iridocorneal angle is not totally closed. In this case, the IOP and the symptoms are alleviated.
    • Chronic glaucoma, i.e., a continually high IOP, resulting from a narrow iridocorneal angle, closed in several places called synechies.

  • On the other hand, the primitive open-angle glaucoma (because the iridocorneal angle is open), which are always chronics. These are the most frequent and we distinguish among them:
    • The high IOP glaucoma, leading to the progressive death of nerve cells and a decrease in visual field. In this case, high IOP is not due to a closed iridocorneal angle but to a congestion of the trabeculum.
    • The high IOP glaucoma with neither visible glaucomatous alteration nor simple ocular hypertension. In this case, there is still no symptoms yet, but the IOP is high and the risk that they appear is serious.
    • Normal IOP glaucoma, which is not very different from the high IOP glaucoma since the damages are similar and the treatments are more or less the same. However, there are specific alterations of the normal IOP glaucoma, that will help your eye specialist to diagnose it.

  • The secondary glaucoma, successive to another eye disease or treatment.

Note:
The optic nerve, which connects the eye to the brain, ensures the transmission of signals from the retina to the central nervous system where they are processed as images.

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Epidemiology

Glaucoma is a common medical condition, as it affects approximately 2% of the population. In Belgium, 2% of subjects older than 40 years of age suffer from glaucoma2. In Morocco, 400,000 subjects are affected by open-angle glaucoma3. In the United States, it is estimated that 2.2 million Americans (1.86% of the population) older than 40 years of age present open-angle glaucoma4. In France, almost 600,000 people are diagnosed with glaucoma, and the disease is present in another 400,000 people who are not aware of it5.

Its frequency increases with age, and it occurs especially after the age of 50, but also affects children5. In this case, it is called congenital glaucoma.

In industrialized countries, glaucoma is the leading cause of blindness5.

2 Bulletin trimestriel La canne blanche. Ligue braille. N°4 2005. p. 12-5.
3 Association Marocaine contre le Glaucome. « Ouvrons l’œil, il y a un voleur de la vue: le glaucome ». Mars 2009.
4 The eye disease prevalence research group. Prevalence of open-angle glaucoma among adults in the United States. Arch Ophthalmol 2004;122:532-8.
5 Nordmann JP, Denis P. Est-ce une affection fréquente ? Dans: Glaucome, Bash 2008, p 47.

 

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