Definition and Overview

Glaucoma is a chronic and progressive eye condition. It is characterised by irreversible damage to the optic nerve, which is responsible for transmitting light-generated nerve impulses to the brain.

During the early stages, a person with glaucoma does not experience any noticeable symptoms. This is the reason why the condition is often diagnosed when it has already progressed and caused significant damage to the optic nerve. When left untreated, patients will develop varying degrees of vision problems that can eventually lead to total blindness. Thus, regular eye examinations are recommended, especially for those who have an increased risk of developing the condition.

There are different types of glaucoma, namely:

  • Open-angle glaucoma - This type occurs when the eye’s drainage canal is clogged, preventing fluid from draining. This results in increased pressure on the optic nerve. The nerve then gradually gets damaged and blind spots begin to develop in the field of vision.

  • Angle-closure glaucoma - This condition is characterised by the abnormal drainage of fluid due to a narrowed angle between the iris and cornea. Basically, the iris gets in the way of proper fluid drainage, leading to a sudden buildup of eye pressure. This form, which is associated with cataracts and farsightedness, can develop either gradually (chronic angle-closure glaucoma) or suddenly (acute angle-closure glaucoma). The latter requires immediate medical attention because it can trigger the sudden dilation of pupils.

  • Normal-tension glaucoma - A form of open-angle glaucoma characterised by optic nerve damage that occurs despite normal pressure inside the eye. The reason why normal-tension glaucoma develops is not fully understood. However, doctors believe that it could happen if the optic nerve is more sensitive than normal or it does not get enough blood supply.

Causes of Condition

Glaucoma commonly develops when the intraocular pressure becomes abnormally high, resulting in damage to the optic nerve. Intraocular pressure maintains the tone and shape of the eye. If it becomes too low, the eye softens. On the other hand, if it becomes too high, the eye becomes harder. The latter puts delicate fibers of the optic nerve at risk of damage.

Other less common causes of glaucoma include:

  • Blocked blood vessels in the eye

  • Certain inflammatory conditions

  • Injury to the eye caused by certain chemicals or blunt force

  • Previous eye surgery for another eye condition

  • Severe eye infection

Some factors that can increase a person’s risk of developing glaucoma include a family history of the disease and diabetes.

Because the effects of glaucoma are irreversible, it is important for people with risk factors to take every measure to prevent it from developing. This is possible by undergoing a complete eye exam once every one to two years. Eye specialists can detect increased intraocular pressure or narrowed drainage angle even before any damage to the optic nerve occurs.

Key Symptoms

Many people with glaucoma normally do not show any symptoms during the early stages. Thus, they are often diagnosed when the disease has already progressed to an advanced stage. Often, patients seek treatment when they have already lost their peripheral vision or suffering from other symptoms, including sudden eye pain, blurred vision, and headache.

Who to See and Types of Treatments Available

Patients showing signs of glaucoma, as well as those who have an increased risk of developing the condition, should consult an eye specialist (ophthalmologist) as early as possible. To diagnose the condition, a series of tests will be performed. These include:

  • Optic nerve examination

  • Tonometry, which measures the pressure inside the eye

  • Pachymetry, which measures the thickness of the cornea

The results of these tests are usually enough to confirm a glaucoma diagnosis. If more tests are needed, patients may also undergo:

  • Gonioscopy - Used to visually examine the drainage area and angle of the eye using a special type of contact lens equipped with mirrors.

  • Ophthalmoscopy - Used to detect signs of glaucoma, including changes in the colour of the optic nerve, which may indicate damage due to increased intraocular pressure or poor blood flow. The test is also used to determine if the cupping of the optic discs in both eyes is asymmetrical, which is a strong indication of glaucoma.

Treatment

Glaucoma treatment focuses on preventing the condition from getting worse by stabilising intraocular pressure and protecting the optic nerve from further damage. Treatment options for glaucoma include:

1.) Glaucoma eye drops - Eye drops are the first line of treatment for glaucoma patients. They work by reducing fluid formation in the eye while increasing fluid outflow to keep intraocular pressure under control. Although very effective in the majority of cases, some patients experience side effects, such as stinging, allergies, eye irritation, and blurred vision. Some severe side effects are also reported, including emphysema, bradycardia, fatigue, and low blood pressure. In cases of severe side effects, the doctor often elects to discontinue the therapy and explore other treatment options.

2.) Laser therapy - Laser treatment for glaucoma includes:

  • Laser iridotomy - Involves creating a hole on the outer edge of the iris using a focused beam of light to allow excess fluid to drain.

  • Argon laser trabeculoplasty - Involves focusing laser beams to the trabecular meshwork that encircles the iris to drain excess fluid.

  • Diode laser cycloablation - In this therapy, the laser targets the ciliary body that produces the aqueous humor to lower pressure in the optic nerve. This laser therapy has shown great results in the treatment of open-angle glaucoma and is known to cause very few side effects. The procedure is often followed by long-term use of glaucoma eye drops to control intraocular pressure.

3.) Glaucoma surgery - For severe cases, glaucoma can be treated surgically through a procedure called trabeculectomy. This is a microsurgical procedure in which a small piece of trabecular meshwork is removed from the eye to create a new drainage pathway for eye fluid.

References:

  • Alward WLM. “Medical management of glaucoma.” N Engl J Med. 1998; 339:1298-1307. http://www.nejm.org/doi/full/10.1056/NEJM199810293391808

  • Lin SC. “Medical management of glaucoma.” Journal of Glaucoma. October 2003; 12(5):449. http://journals.lww.com/glaucomajournal/Citation/2003/10000/Medical_Management_of_Glaucoma.15.aspx

  • Singh K, Shrivastava A. “Medical management of glaucoma: Principles and practice.” Indian J Ophthalmol. 2011 Jan; 59(Suppl1): S88-S92. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3038497/

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