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.
The nerve damage involves loss of retinal ganglion cells in a characteristic pattern. There are many different subtypes of glaucoma, but they can all be considered to be a type of optic neuropathy. Raised intraocular pressure (above 21 mmHg or 2.8 kPa) is the most important and only modifiable risk factor for glaucoma. However, some may have high eye pressure for years and never develop damage, while others can develop nerve damage at a relatively low pressure. Untreated glaucoma can lead to permanent damage of the optic nerve and resultant visual field loss, which over time can progress to blindness.
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.
Glaucoma has been called the "silent thief of sight" because the loss of vision often occurs gradually over a long period of time, and symptoms only occur when the disease is quite advanced. Once lost, vision can not normally be recovered and so treatment is aimed at preventing further loss.
Signs and symptoms
There are two main types of glaucoma: open-angle glaucoma and closed-angle glaucoma (also called angle closure glaucoma). Open-angle glaucoma accounts for 90% of glaucoma cases in the United States. It is painless and does not have acute attacks. The only signs are gradually progressive visual field loss, and optic nerve changes (increased cup-to-disc ratio on fundoscopic examination).
Closed-angle glaucoma accounts for less than 10% of glaucoma cases in the United States, but as many as half of glaucoma cases in other nations (particularly Asian countries). About 10% of patients with closed angles present with acute angle closure crises characterized by sudden ocular pain, seeing halos around lights, red eye, very high intraocular pressure (>30 mmHg), nausea and vomiting, sudden decreased vision, and a fixed, mid-dilated pupil. It is also associated with a oval pupil in some cases. Acute angle closure is an emergency.
Types of Glaucoma
There are four main types of Glaucoma.
Chronic Glaucoma - The most common, when the drainage channels become blocked slowly over many years. The eye pressure rises very slowly and there is no pain to show there is a problem. But the field of vision gradually becomes impaired. Once damage is done it cannot be repaired. However with early diagnoses and regular check ups and treatment, damage can be kept to minimum
Acute Glaucoma - This happens when there is a sudden and more complete blockage to the flow of the fluid to the eye. This is because the narrow angle closes to prevent fluid getting to the drainage channel. The eye becomes red, vision deteriorates and you may even faint. You may also experience nausea and vomiting. In the early stages you may see coloured rings around white lights. This can be very painful and will cause permanent damage if not treated promptly. In some cases Acute Glaucoma does not always cause sudden pain. You can have a series of mild attacks, often in the evening. There may be some discomfort in the eye, coloured lights around a white light, and hazy vision. If you experience either of these systems you should contact your Doctor.
Secondary Glaucoma - Two other main types of glaucoma occur when a rise in eye pressure is caused by another eye condition. This is known as secondary glaucoma. Secondary glaucoma can develop as a complication of other medical conditions. They are sometimes associated with eye surgery or advanced cataracts, eye injuries, certain eye tumours, or uveitis (eye inflammation). Pigmentary Glaucoma occurs when pigment from the iris flakes off and blocks the meshwork, slowing fluid drainage. Neovascular Glaucaoma is linked to diabetes.
Congnital Glaucomma (Buphthalmos) - Over 80% of cases are diagnosed in the first three months of life. Due to an abnormality of the angle of the anterior chamber, blocking drainage.
Causes
There are several causes for glaucoma. Ocular hypertension (increased pressure within the eye) is the most important risk factor in most glaucomas, but in some populations, only 50% of people with primary open angle glaucoma actually have elevated ocular pressure.
Treatment
The treatment aims to reduce the pressure in the eye, either by helping fluid to drain out of your eye or by reducing the amount of fluid produced. For treatment of Glaucoma there is used:
Medication
Intraocular pressure can be lowered with medication, usually eye drops.
Surgery
Both laser and conventional surgeries are performed to treat glaucoma.
Surgery is the primary therapy for those with congenital glaucoma.
Generally, these operations are a temporary solution, as there is not yet a cure for glaucoma.
Canaloplasty
Canaloplasty is a nonpenetrating procedure using microcatheter technology.
Laser surgery
Laser trabeculoplasty may be used to treat open angle glaucoma. It is a temporary solution, not a cure.
Trabeculectomy
The most common conventional surgery performed for glaucoma is the trabeculectomy. Here, a partial thickness flap is made in the scleral wall of the eye, and a window opening is made under the flap to remove a portion of the trabecular meshwork. The scleral flap is then sutured loosely back in place to allow fluid to flow out of the eye through this opening, resulting in lowered intraocular pressure and the formation of a bleb or fluid bubble on the surface of the eye.
Glaucoma drainage implants
Laser-assisted nonpenetrating deep sclerectomy
The most common surgical approach currently used for the treatment of glaucoma is trabeculectomy, in which the sclera is punctured to alleviate intraocular pressure.
