Glaucoma, commonly known as silent blindness, is an ocular pathology that gradually reduces peripheral vision. Today, it is the second leading cause of preventable and irreversible blindness, affecting more than 70 million people worldwide. It is known that some types of glaucoma have a genetic predisposition. However, there are no studies with conclusive results that relate it to certain life styles or habits. Our specialist in Ophthalmology, Dr. Alberto González Costea, talks about the keys to understanding this disease and encourages us to perform periodic ophthalmologic examinations to detect it in time.
What are the main characteristics of glaucoma?
Glaucoma is a multifactorial ocular pathology. Intraocular pressure is one of the risk factors, although assessment of the optic nerve and visual field is also necessary for diagnosis.
Intraocular pressure is due to aqueous humor. This is produced, circulated and evacuated in the anterior segment of the eye, specifically in the iridocorneal angle. An imbalance between the production and evacuation of aqueous humor leads to an increase in intraocular pressure, which in turn damages and can compromise other ocular structures such as the optic nerve.
In addition, it is important to remember that intraocular pressure varies throughout the day.
Glaucoma can be classified into two broad categories: open-angle glaucoma and angle-closure glaucoma. In turn, both types may themselves be primary diseases. On the contrary, secondary glaucomas may be the result of trauma, certain treatments such as corticosteroids, inflammation, tumors or conditions such as pseudoexfoliation of the lens or pigmentary dispersion.
- Primary congenital glaucoma: affects 0.3 to 1 out of every 10,000 newborns or infants up to 3 years old. Eighty percent of patients with this type of glaucoma have involvement of both eyes. Only 10-20% of cases are due to genetic inheritance. The cause of this glaucoma is an alteration in the development of the structures of the angle through which the evacuation of the aqueous humor should take place.
- Primary infantile-juvenile glaucoma: it occurs in patients between 3 and 40 years of age.
- Primary open angle glaucoma: represents 65% of glaucomas and presents with elevated IOP (greater than 21 mmHg). In these cases the structures responsible for the evacuation of the aqueous humor are anatomically normal. There are several genes involved and it is more frequent in myopes.
- Normal pressure glaucoma: Intraocular pressure figures are within normal limits, but there is still optic nerve damage.
- Angular closure glaucoma and phacolytic glaucoma: occurs in small eyes in which the iridicorneal angle is narrow, which does not allow the aqueous humor to escape.
How can we detect the first symptoms?
Contrary to what we may think, visual acuity will not deteriorate until very late stages of this disease. Thus, glaucoma patients may not perceive changes in their vision. For this reason, prevention and early detection are essential. The way to detect and treat it is carried out after exhaustive ophthalmological examinations. In these examinations, intraocular pressure and corneal thickness values are contrasted. In addition, tests such as visual field assessment (visual campimetry) are performed and the optic nerve is explored under pupillary mydriasis (dilation).
One of the most innovative diagnostic tests that provides great information about ocular structures is optical coherence tomography (OCT). Thanks to it we can measure the width of the iridocorneal angle and assess whether the optic nerve has been damaged.
What is the prognosis for patients?
Patients can control their intraocular pressure by administering ocular hypotensive eye drops. In Spain, the most commonly used eye drops are prostaglandin derivatives, to promote the outflow of aqueous humor, and beta-blockers, to reduce the formation of aqueous humor.
In some cases, if medical treatment with eye drops does not control the disease, surgical treatment will be necessary.
In patients with narrow angle glaucoma, prophylactic treatment is usually carried out in order to avoid an episode of acute glaucoma, i.e., a sudden rise in intraocular pressure due to pupillary block.
It is important to keep in mind that all patients with glaucoma require follow-up with periodic ophthalmological controls in which not only intraocular pressure values are measured but also the possible variations of the visual field and the optic nerve.