What is glaucoma and its types?

glaucoma

Glaucoma is a severe eye disorder that can lead to blindness. Those affected do not usually have symptoms for years, so consulting an ophthalmologist is the only way to detect it early.

The glaucoma is the set of processes in which an increased intraocular pressure produces lesions primarily affecting the optic nerve, causing a loss of visual field that may become full if the process does not stop. It is the second leading cause of blindness in the world, behind diabetes. It is estimated that between 15-20% of blind people have lost their vision due to glaucoma.

The incidence of glaucoma increases with age. It is estimated that two out of every hundred people over 45 years of age and almost 4% of those over 70 years of age suffer from it. In total, the WHO estimates that it affects more than 60 million people globally – around one million of them in Spain – and future forecasts suggest that in 2020 the figure could approach 76 million. 

Glaucoma often has no noticeable symptoms until it is too late and vision has already been permanently affected. For this reason, experts advise that everyone over 45 years of age has an annual check of intraocular pressure. It is estimated that half a million Spaniards suffer from it without being diagnosed. In this case, early diagnosis is essential since, although the disease has no turning back, if it is detected early, it can be controlled. Its progression delayed, avoiding the dreaded consequence of blindness in up to 95% of cases. 

It must be taken into account that there are risk factors that can increase the options of suffering from glaucoma, so leading healthy lifestyle habits, such as avoiding obesity, tobacco, alcohol, or physical inactivity, will help reduce the risk of developing glaucoma, the leading cause of irreversible blindness in people over 60 years of age.

What causes the intraocular pressure to increase is the aqueous humor, a transparent liquid that provides nutrition to the eye’s structures and whose normal pressure is 15 millimeters of mercury (mmHg). To understand the mechanism of glaucoma production, it is necessary to know how aqueous humor is formed and eliminated since alterations at this level are what will cause the disease.

Physiology of the aqueous humor

In the anterior part of the eye, we can distinguish (inside) two chambers: the anterior chamber and the posterior chamber. Both rooms are those that contain aqueous humor. They are separated by the lens but communicate through the iris.

In the posterior chamber are structures called ciliary bodies, which are those that produce aqueous humor. Once created, it passes to the posterior chamber, and from there, it will pass to the anterior chamber through the pupil. In the anterior chamber, the fluid is eliminated through channels that lead to the general venous system.

The increase in intraocular pressure may be due to the rise in the production of aqueous humor (rare) or to an alteration in its elimination (it is the most common).

Types and causes of glaucoma

Depending on the cause that causes it, we can speak of primary or secondary glaucoma. Primary glaucoma is understood not to be caused by any other alteration at the ocular level. Secondary glaucoma occurs due to another visual alteration or due to adverse effects of the medication.

There are different types of glaucoma, depending on the level of the alteration in the eye:

Open-angle glaucoma:

it is the most common of all and can be primary or secondary. The alteration is found in the channels that make the aqueous humor pass from the anterior chamber to the venous circulation, so eliminating the aqueous humor is altered. The angle through which fluid passes from the posterior chamber to the anterior chamber remains open (this is why it is called open-angle glaucoma).

Narrow-angle glaucoma:

it can also be primary or secondary, and, in this case, the alteration is in the angle between the posterior and anterior chamber (at the level of the iris), which remains closed and hinders the passage of aqueous humor from one camera to another.

Glaucoma risk factors and groups

Various factors can increase the chances of a person suffering from some glaucoma, and many of them are controllable and reversible, so it is convenient to know them to avoid this problem as much as possible. Likewise, various population groups must take into account, even more, the need to go to an ophthalmological examination to detect its appearance in time:

  • Smoking or consuming alcohol.
  • Sedentary lifestyle or lack of physical activity.
  • Obesity.
  • Having a family history of glaucoma, especially if it is direct relatives such as parents or siblings.
  • People of African or Asian race.
  • People with high myopia (greater than five diopters) or as a consequence of the evolution of other pathologies, which can be both ocular and systemic. Among the first, uveitis, alterations of the retina, alterations of the lens, intraocular tumors, detachment of tissue from the different structures inside the eye stand out. The optic nerve of myopic eyes is more susceptible to injury than that of non-shortsighted.
  • People over 45 have not had an eye exam in recent years.
  • Patients with elevated intraocular pressure. 
  • Corticosteroid medicated patients.
  • People who have suffered a blow or trauma to the eye.
  • People with diabetes, since increased blood glucose levels, can cause severe damage to the retina (diabetic retinopathy).
  • Women who have experienced a hormonal change as a result of, for example, pregnancy or menopause.

In case you are affected by any of these factors, experts advise you to go to an optician-optometrist to undergo non-contact tonometry, a simple, quick, and painless exam with which intraocular pressure is measured along with a campimetry and a fundus examination.