Glaucoma

Definition
According to WHO, glaucoma is the second leading cause for blindness in the world. It affects more than 60 million people and this number will grow up to 80 million by 2020. Along with macular degeneration, cataract and diabetic retinopathy, glaucoma is one of the most common age-related eye diseases.

Glaucoma is mostly associated with increased pressure within the eye that compresses the optic nerve and leads to its atrophy. As glaucoma damages the optic nerve and the nervous tissue does not regenerate, glaucoma leads to a progressive non reversible sight loss.

Causes
The inner of the eye contains structures filled with fluid, known as aqueous humor, which is drained towards the venous system through a channel situated between the iris and the cornea. If this channel gets blocked or if the liquid production exceeds its own elimination, the intraocular pressure increases, causing glaucoma. The exact reason for the channel blockage is not clear.  

However you should know that there is normal-tension glaucoma. The reasons for its development remain unclear. It may be due to too sensitive optic nerve or limited blood flow towards the nerve.

There are other less common causes of glaucoma, inflammatory process in the eye, trauma, - eye blood vessel obstruction or secondary after eye surgery.

Risk factors for glaucoma include:

• High intraocular pressure
• Being African-American, Japanese, Hispanic, Scandinavian, Russian
• Age over 60 for the general population and over 40 for African-American and Hispanic
• Family history of glaucoma
• Previous eye trauma or eye surgery for treating another condition
• High degree myopia
• Long-term use of corticosteroids, such as prednisolone
• Medical conditions such as diabetes, high blood pressure, heart failure, anemia
• Anatomical predisposition- thin cornea, narrow irido-corneal angle

Types of glaucoma

There are two main types of glaucoma:
• Open-angle glaucoma- also known as wide-angle glaucoma, is more common- 75% of the patients have this type of glaucoma. Although the eye structures are normal, the drainage of the intraocular liquid is poor, which causes gradual increase of the blood pressure.
• Closed-angle glaucoma- or narrow-angle glaucoma is characterized by very narrow angle between the iris and the cornea, as its name shows. When the angle is too narrow it could be physically blocked by the iris. This is called acute closed-angle glaucoma and it is an emergency that requires immediate medical help as it can lead to blindness within a couple of days. Otherwise narrow-angle glaucoma may also be chronic as the open-angle one.

Symptoms
The clinical manifestation of the glaucoma depends on its type. Changes in glaucoma are usually binocular. 

Open-angle glaucoma may remain symptomless at the early stages. With the advance of the condition, the peripheral vision begins to suffer and the patient may notice blind spots in his visual field. In the later stages the loss of peripheral vision progresses. That’s why advanced glaucoma is characterized by tunnel vision.

Chronic angle-closure glaucoma like wide-angle glaucoma shows no symptoms and progresses slowly.

On the other side, acute narrow-angle glaucoma is a dramatic condition that cannot remain unspotted. It is characterized by: severe eye pain, headache, redness in the eye, nausea, vomiting, blurred vision, halos around lights. If you ever experience some of this symptoms, you need to seek immediately for medical care.

Diagnosis
To diagnose glaucoma, an ophthalmologist (eye doctor) will perform several tests, including:
• Measuring of  the intraocular pressure (also named tonometry)
• Measuring of the irido-corneal angle (or goniometry)
• Measuring of the thickness of the cornea (known as pachymetry)
• Tests to determine the size of the visual field (perimetry)
• Ophthalmoscopy- after dilatation of the pupils, this test allows to visualize the shape and the color of the optic nerve, which is the main structure damaged by glaucoma

Treatment
As mentioned above the destruction of the optic nerve is not reversible. But the right treatment can slow the process down with years and even prevent blindness if diagnosed on time. The main target is to decrease the intraocular pressure in order to stop the compression of the optic nerve and preserve the vision left. Depending on the patient’s condition, this could be achieved through eye drops, surgery or laser treatment.

Eye drops are usually the medications of first choice for glaucoma. Some types of eye drops approve the drainage of the humor aqueous, while other diminish its production.

As for laser treatment, there are several procedures that could be performed:
• Trabeculoplasty- the laser is used to open the trabecules of the irido-corneal angle and therefore to improve the drainage of the eye
• Iridotomy- a tiny hole is created into the iris to facilitate the flow of the intraocular fluid
• Cyclophotocoagulation- some areas of the eye responsible for the production of liquid are treated with laser in order to decrease its production.

Surgical approaches in glaucoma treatment include the creation of new drainage channel to replace or aid the malfunctioning one.

Conclusion
Seriousness of glaucoma evolves from the fact that the condition is still incurable. Moreover half of the patients with glaucoma are not aware of their condition, which greatly increases the risk of early blindness. These facts underline the need of regular eye checks for the risk groups as well as for the general population.