Glaucoma is a disease that results in damage to the optic nerve. The optic nerve carries visual information from the eye to the brain. Glaucoma is usually caused by fluid build-up in the front part of the eye. The extra fluid increases the pressure in the eye, damaging the optic nerve.
What causes Glaucoma?
The eye constantly produces fluid known as the aqueous humor. As the aqueous flows into the eye, the same amount should flow out. The fluid drains out through structures called the trabecular meshwork. This meshwork is part of the anterior chamber angle or the drainage angle. If the drainage angle is not functioning properly, fluid builds up. This results in increased eye pressure and damage to the optic nerve.
Types of Glaucoma
Primary Open-Angle Glaucoma
This Is the most common type of glaucoma. It happens gradually when the eye does not drain fluid as it should. As a result, eye pressure builds and begins to damage the optic nerve. This form of glaucoma is painless and causes no vision changes initially.
Some individuals can sustain damage to their optic nerves at a relatively low pressure. This increases their risk of developing glaucoma. Regular examinations are important to find early signs of damage to their optic nerves.
Angle-Closure Glaucoma (Narrow-Angle Glaucoma)
This type of glaucoma develops when someone's iris is very close to the drainage angle of their eye. The iris can end up blocking the drainage angle. This can result in a very rapid increase in eye pressure known as an
"acute attack". It is a true eye emergency that requires immediate treatment to lower eye pressure to preserve vision.
Signs of an Acute Angle-Closure Glaucoma Attack:
Vision becomes suddenly blurry
Severe Eye Pain
Nausea and possible vomiting
Rainbow-colored rings or haloes around lights
Many people with angle-closure glaucoma develop it slowly. This is called Chronic angle-closure glaucoma. There may be no symptoms at first, permitting damage to become severe before the individual is aware there is a problem. The first symptoms may not occur until an acute attack develops. Chronic angle-closure glaucoma is found in roughly 70% of narrow-angle glaucoma patients, with only 30% developing a sudden blockage.
Who is at risk for Glaucoma?
Some people have a higher than normal risk of developing glaucoma. This includes individuals who:
are over the age of 40
have family members with glaucoma
are of African or Hispanic heritage
have high eye pressure
are farsighted or nearsdighted
have had an eye injury
have thin central corneas
have thinning of the optic nerve
have diabetes, migraines, or poor circulation
How is Glaucoma diagnosed?
The only way to diagnose glaucoma is with a comprehensive eye examination. A glaucoma screening that only checks eye pressure is not sufficient to rule-out glaucoma.
During a glaucoma evaluation, your eye doctor will:
measure your eye pressure
inspect your eyes drainage angle
inspect your optic nerves for damage
perform a visual field test
perform detailed imaging of the optic nerves
measure retinal nerve fiber layer thicknesses
measure central cornea thicknesses
Eye With Glaucoma
Drainage Structures Unable To Drain Aqueous Fluid Adequately
Pressure Increased Causing Damage
To The Optic Nerve
How is Glaucoma treated?
Glaucoma damage is permanent and cannot be reversed. The goal of treatment is to prevent further damage to the optic nerves. Treatment may consist of:
Glaucoma is usually treated with medication in the form of eyedrops. The drops are used on a daily basis to lower eye pressure. Some of these medications achieve lower eye pressure by reducing fluid production in the eye, others can enhance the drainage of fluid.
Surgery may be employed when medications are ineffective at lowering intraocular pressure. The most common surgical procedures utilized to treat glaucoma are:
Laser Trabeculoplasty - this procedure is perfomed on patient with open-angle glaucoma. The laser is directed at the drainage angle in an effort to increase the outward flow of fluid.
Iridotomy - This procedure is used to treat angle-closure glaucoma. The laser is used to create a small opening in the iris to enhance the flow of fluid to the drainage angle.
Operating Room Procedures:
Trabeculectomy - This procedure involves a small wedge of the iris being removed (iridectomy) and the creation of a tiny flap in the sclera (white of the eye). In addition, a small bubble is created in the conjunctiva called a filtration bleb. This is usually hidden under the upper eyelid and cannot be seen. The goal is to allow additional fluid to drain from the eye through the scleral flap into the bleb. The fluid will be absorbed by the tissue around the eye, lowering eye pressure.
Glaucoma Drainage Devices - This procedure consists of the implanting of a tiny drainage tube into the eye. It sends the fluid to a collection area. This reservoir is created under the conjunctiva where fluid accumulates and then is absorbed into the nearby blood vessels.