Open angle:

This type of glaucoma is a disease which causes gradual and imperceptible loss of vision. There are no previous symptoms or pain. It develops slowly and often shows no signs for years. Most patients with this glaucoma usually feel well and don’t notice any visual loss. This is because the initial loss of vision is on the sides of the visual field (peripheral vision). When the patient realises the loss of vision, the glaucoma is usually very advanced. Without treatment, the glaucoma can lead to blindness.
It is therefore important to detect open-angle glaucoma early.

Closed angle:

The following symptoms may vary or appear and disappear. People with closed-angle glaucoma may notice:

• Sudden pain in the eye, in the forehead or head.
• Decreased or blurred vision.
• Coloured halos around lights
• Sensation of inflammation.
• Reddening of the eyes.
• Nausea and/or vomiting.

• Tonometry:

This the measurement of intraocular pressure in the eye. The normal range of pressures is from 12 to 22 (measured in millimetres of mercury). In most glaucoma cases, pressures are found exceeding 20. In any case, there are cases that develop glaucoma with pressures between 12 and 20 (low-tension glaucoma).

• Ophthalmoscopy:

This diagnostic test allows the doctor to examine your optic nerve to check the damage caused by glaucoma. In this test, the eye is dilated and the doctor uses a small device with a magnifying glass and a light on the end that allows him to see the optic nerve in detail.
If the intraocular pressure is not in the normal range or the optic nerve does not have a normal appearance, your doctor can give you two additional tests for glaucoma: Perimetry and gonioscopy.

• Perimetry

Perimetry is a visual test in which a map of your visual field is generated. This test will let the doctor know if your vision has been affected by glaucoma. In this test, the patient is required to look ahead and indicate when they see a blip in their peripheral vision. This allows an accurate map of the patient’s vision to be created.

• Gonioscopy:

This test allows us to determine if the angle between the iris and cornea is open or closed.

• Pachymetry:

Pachymetry is a simple, painless test by which we measure the thickness of the cornea (the outer transparent layer of the eye). Pachymetry can help diagnosis because the corneal thickness has a direct influence on the interpretation of intraocular pressure tests. An eye with a thick cornea (high pachymetry values) may have increased intraocular tension without being a problem. There are formulas that establish a correlation between corneal thickness and intraocular pressure values.

There are several types of glaucoma, the two most important of which are open angle and closed angle glaucoma. Both are characterised by increased intraocular pressure in the eye.

Open angle glacuoma

This is the most common type of glaucoma, making up 90% of cases of glaucoma:

• It is caused by a slow clogging of drainage channels which leads to increased eye pressure.
• The angle between the iris and the cornea is open, normal.
• It develops slowly and is a condition for life.
• It leads to symptoms and damage that are not seen immediately by the patient.

Open-angle glaucoma is also called primary or chronic glaucoma.

Closed angle glacuoma

This is the least common type:

• It is caused by a blockage of drainage channels, resulting in a sudden increase in intraocular pressure.
• It has a closed or narrow angle between the iris and cornea.
• It develops rapidly.
• It leads to symptoms and damage that are quickly seen.
• It requires immediate medical attention.

Normal tension glacuoma

Also called low tension, in this type the optic nerve is damaged even when eye pressure is not high. It is not yet known why there is damage to optic nerves while the intraocular pressure is normal.

Congenital glacuoma

This type of glaucoma occurs in babies when there is incomplete or incorrect development of the drainage channels of the eye before birth. It is a rare disease that can be inherited.
Glaucoma can be treated either by medication or surgery.

Medication

Eye Drops

Eye drops are usually the most common treatment. They work by reducing eye pressure in two ways:

• Decreasing the amount of aqueous humour produced.
• Improving fluid flow through the drainage channels.

These eye drops are to be applied virtually on a daily basis. It is very important to follow the prescription from your eye doctor.

Tablets:

Sometimes when the eye drops do not sufficiently control the intraocular pressure, tablets can be added. These tablets also cause a decrease in the generation of aqueous humour. The frequency of these tablets is usually 2 to 4 times per day.
Surgical treatment:

Laser Surgery:

1. a) Laser surgery is a commonly practised procedure although with varying success rates in the long term. The technique used is known as trabeculoplasty. This technique takes from 10-15 minutes, is painless and can be performed on an outpatient basis. Here a laser is applied to the drainage channels so that fluid passing through flows more easily, reducing the pressure inside the eye.
   The laser treatment often causes a decrease in the pressure over time while allowing the patient to continue with their medication. In other cases, the effect is not sufficient. The result therefore is variable and must be examined by an ophthalmologist.
   There are currently two types of trabeculoplasty for open-angle glaucoma:

• Argon Laser Trabeculoplasty: (ALT) – Open Angle.
  – This treatment decreases the intraocular pressure in about 75% of patients. It can only be done two or three times in each eye in total.
• Selective Laser Trabeculoplasty (SLT) – closed angle.
  – This technique is more novel than before and uses very low power settings, leaving parts of the trabecular meshwork intact. By leaving areas of the trabecular meshwork intact, it is considered that this technique can be repeated safely. Some ophthalmologists refer to the combination of both treatments as effective for decreasing pressure.

1. b) Laser Peripheral Iridotomy:

This procedure is used to make a hole in the iris, allowing fluid to pass under the iris into the anterior chamber, bypassing its natural path. It is the most widely used treatment for closed-angle when there is some kind of pupillary blockage.

1. c) Cycloablation:

A laser is applied to the ciliary body to reduce the production of aqueous humour. It is performed when the above described procedures have been carried out unsuccessfully.

Traditional surgery:

1. a) Non-penetrating deep sclerectomy with or without implants

It is the technique of choice when medical treatment fails.

1. b) Trabeculectomy:

When neither medication or laser techniques manage to lower intraocular pressure, some doctors may recommend a trabeculectomy. In it, the surgeon creates a conduit in the sclera that allows the fluid within the eye to escape.

1. c) Drain valve implant

Multiple elements have been developed to help the drainage of aqueous humour from the eye. All these elements have a similar design and consist of a small silicone tube connecting the interior of the anterior chamber of the eye with the ocular surface. This type of surgery reduces intraocular pressure less than a trabeculectomy.