Glaucoma is a complicated disease in which damage to the optic nerve leads to progressive, irreversible vision loss. Glaucoma is the second leading cause of blindness. Glaucoma is an eye disease in which the optic nerve is damaged in a characteristic pattern. This can permanently damage vision in the affected eye(s) and lead to blindness if left untreated. It is normally associated with increased fluid pressure in the eye (aqueous humour). The term ‘ocular hypertension’ is used for people with consistently raised intraocular pressure (IOP)without any associated optic nerve damage. Conversely, the term ‘normal tension’ or ‘low tension’ glaucoma is used for those with optic nerve damage and associated visual field loss but normal or low IOP.
Categories of Glaucoma
Glaucoma can be roughly divided into two main categories, “open angle” and “closed angle” (or “angle closure”) glaucoma. The angle refers to the area between the iris and cornea, through which fluid must flow to escape via the trabecular meshwork. Closed angle glaucoma can appear suddenly and is often painful; visual loss can progress quickly, but the discomfort often leads patients to seek medical attention before permanent damage occurs. Open angle, chronic glaucoma tends to progress at a slower rate and patients may not notice they have lost vision until the disease has progressed significantly.
Causes of Glaucoma
Open-Angle (Chronic) Glaucoma is the most common type of glaucoma.
- The cause is unknown. An increase in eye pressure occurs slowly over time. The pressure pushes on the optic nerve.
- Open-angle glaucomatends to run in families. Your risk is higher if you have a parent or grandparent with open-angle glaucoma. People of African descent are at particularly high risk for this disease.
Angle-Closure (Acute) Glaucoma occurs when the exit of the aqueous humor fluid is suddenly blocked. This causes a quick, severe, and painful rise in the pressure in the eye.
- Angle-closure glaucoma is an emergency. This is very different from open-angle glaucoma, which painlessly and slowly damages vision.
- If you have had acute glaucoma in one eye, you are at risk for an attack in the second eye, and your doctor is likely to recommend preventive treatment.
- Dilating eye drops and certain medications may trigger an acute glaucoma attack.
Congenital Glaucoma is seen in babies. It often runs in families (is inherited).
- It is present at birth.
- It is caused by abnormal eye development.
Secondary Glaucomais caused by:
- Drugs such as corticosteroids
- Eye diseases such as uveitis
- Systemic diseases
Symptoms of Glaucoma
- Most people have no symptoms
- Once vision loss occurs, the damage is already severe
- There is a slow loss of side (peripheral) vision (also called tunnel vision)
- Advanced glaucoma can lead to blindness
- Symptoms may come and go at first, or steadily become worse
- Sudden, severe pain in one eye
- Decreased or cloudy vision, often called “steamy” vision
- Nausea and vomiting
- Rainbow-like halos around lights
- Red eye
- Eye feels swollen
- Symptoms are usually noticed when the child is a few months old
- Cloudiness of the front of the eye
- Enlargement of one eye or both eyes
- Red eye
- Sensitivity to light
Risk Factors of Glaucoma
Awareness and early detection of glaucomaare extremely important because this disease can be successfully treated when diagnosed early. While everyone is at risk for glaucoma, certain people are at a much higher risk and need to be checked more frequently by their eye doctor. The major risk factors for glaucoma include the following:
- Age over 45 years
- Family history of glaucoma
- Black racial ancestry
- History of elevated intraocular pressure
- Nearsightedness (high degree of myopia), which is the inability to see distant objects clearly
- History of injury to the eye
- Use of cortisone (steroids), either in the eye or systemically (orally or injected)
- Farsightedness (Hyperopia), which is seeing distant, objects better than close ones (Farsighted people may have narrow drainage angles, which predispose them to acute [sudden] attacks of angle-closure glaucoma.)
Diagnosis of Glaucoma
An eye doctor (ophthalmologist) can usually detect those individuals who are at risk for glaucoma (because of, for example, a narrow drainage angle or increased intraocular pressure) before nerve damage occurs. The doctor also can diagnose patients who already have glaucoma by observing their nerve damage or visual field loss. The following tests, all of which are painless, may be part of this evaluation.
- Tonometry determines the pressure in the eye by measuring the tone or firmness of its surface.
- Pachymetry is a relatively new test being used for the diagnosis and treatment of glaucoma. Pachymetry determines the thickness of the cornea.
- Gonioscopy is done by numbing the eye with anesthetic drops and placing a special type of contact lens with mirrors inside the eye. The mirrors enable the doctor to view the interior of the eye from different directions. The purpose of this test is to examine the drainage angle and drainage area of the eye. In this procedure, the doctor can determine whether the angle is open or narrow and find any other abnormalities within the angle area.
- Ophthalmoscopy is an examination in which the doctor uses a handheld device to look directly through the pupil (the opening in the colored iris) into the eye. This procedure is done to examine the optic nerve (seen as the optic disc) at the back of the eye. Damage to the optic nerve, called cupping of the disc, can be detected in this way.
- Visual Field testing actually maps the visual fields to detect any early (or late) signs of glaucomatous damage to the optic nerve. This test can be grossly done by having the patient look straight ahead with one eye covered and count the fingers shown by the examiner from the side. More typically, however, visual fields are measured by a computerized assessment.
Treatment of Glaucoma
Immediate treatment for early-stage, open-angle glaucoma can delay progression of the disease. That’s why early diagnosis is very important. Glaucoma treatments include medicines, laser trabeculoplasty, conventional surgery, or a combination of any of these. While these treatments may save remaining vision, they do not improve sight already lost from glaucoma.
- Causes of Glaucoma
- Open-Angle (Chronic)
- Open-angle glaucoma
- Angle-Closure (Acute) Glaucoma
- Congenital Glaucoma
- Secondary Glaucoma
- Risk Factors of Glaucoma
- Diagnosis of Glaucoma
- Treatment of Glaucoma
- New study links caffeinated coffee to vision loss (scienceblog.com)
- S’pore scientists identify new genes linked to glaucoma (todayonline.com)