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Glaucoma

 

What is Glaucoma?

Sometimes called the silent thief of sight, glaucoma can damage your vision so gradually you may not notice any loss of vision until the disease is at an advanced stage.

Glaucoma is a multi-factorial, complex eye disease with specific characteristics such as optic nerve damage and visual field loss. While increased pressure inside the eye (called intraocular pressure or IOP) is usually present, patients with normal range IOP can develop glaucoma.

There is no specific level of elevated eye pressure that definitely leads to glaucoma. On the other hand, there is no lower level of IOP that will absolutely eliminate a person’s risk of developing glaucoma. That is why early diagnosis and treatment of glaucoma is the key to preventing vision loss.

 

Types of Glaucoma

There are two main types of glaucoma:

Open-angle glaucoma. Also called wide-angle glaucoma, this is the most common type of glaucoma. The structures of the eye appear normal, but fluid in the eye does not flow properly through the drain of the eye, called the trabecular meshwork. The eye pressure can be high or “normal”. Normal-tension or low-tension glaucoma is a type of open-angle glaucoma. Open-angle glaucoma can also be divided into primary and secondary open-angle glaucoma. Seconary open-angle glaucoma includes pseudoexfoliation and pigmentary glaucoma.

Angle-closure glaucoma. Also called acute or chronic angle-closure or narrow-angle glaucoma, this type of glaucoma is less common, but can cause a sudden buildup of pressure in the eye which could cause rapid loss of vision. Drainage may be poor because the angle between the iris and the cornea (where a drainage channel for the eye is located) is too narrow, the pupil opens too wide or the lens is too thick (as a cataract is forming), narrowing the angle and blocking the flow of the fluid through that channel.

open-vs-narrow-closed-angle-glaucoma

 

Who Should Be Checked

It is important to have your eyes examined regularly. Your eyes should be tested:

  • before age 40, every two to four years
  • from age 40 to age 54, every one to three years
  • from age 55 to 64, every one to two years
  • after age 65, every six to 12 months

Anyone with high risk factors, should be tested every year or two after age 35.

The following are groups at higher risk for developing glaucoma:

African-Americans

Glaucoma is the leading cause of blindness among African Americans. It is 6-8 times more common in African-Americans than in Caucasians.

People Over Age 60

Glaucoma is more common among older people. You are 6 times more likely to develop glaucoma if you are over 60 years old.

Family History of Glaucoma

The most common type of glaucoma, primary open-angle glaucoma, is inherited. If members of your immediate family (father, mother, brothers, or sisters) have glaucoma, you are at a much higher risk than the rest of the population.

Family history increases risk of glaucoma 4-9 times.

Hispanics (Especially Older Age Groups)

Risk for Hispanic populations is greater than those of predominantly European ancestry, and that the risk increases among Hispanics over age 60.

Asians

Asians appear to be at increased risk for angle-closure glaucoma. Angle-closure glaucoma accounts for less than 10% of all diagnosed cases of glaucoma. Low-tension glaucoma is seen at higher rates in Japan.

Cortico-Steroid Users

A 1997 study reported in the Journal of American Medical Association demonstrated a 40% increase in the incidence of ocular hypertension and open-angle glaucoma in adults who required a steroid inhaler to control asthma. Steroid injections into joints or oral steroids can also increase intraocular pressure.

History of Eye Trauma

Injury to the eye may cause secondary open-angle glaucoma. This type of glaucoma can occur immediately after the injury or many years later.

Blunt trauma or injuries that penetrate the eye can damage the eye’s drainage system, leading to traumatic glaucoma.

The most common cause is sports-related injuries (baseball or boxing are considered high risk sports).

Other Risk Factors

Other possible risk factors include:

High myopia (nearsightedness)

Hypertension

Central corneal thickness less than .5 mm.

 

How is Glaucoma Detected?

  • Tonometry – measurement of the intraocular pressure using anesthetic drops, a blue light source, and an applinator or similar device
  • Ophthalmoscopy – detailed examination of the optic nerve under magnification with a combination of hand-held lenses and a slit lamp
  • Perimetry – a complete mapping of the peripheral vision using a Humphery Field Analyzer or similar device
  • Gonioscopy – examination of the drainage angle of the eye using a special contact lens and a slit lamp
  • Pachymetry – measurement of the thickness of the cornea (the clear, dome-shaped front of the eye)

 

Treatment of Glaucoma

Eye drops for glaucoma. These either reduce the formation of fluid in the front of the eye or increase its outflow. Side effects of glaucoma drops may include allergy, redness of the eyes, brief stinging, blurred vision, and irritated eyes. Some glaucoma drugs may have systemic side effects. Be sure to tell your doctor about any glaucoma medication you are currently taking or are allergic to.

 

Laser surgery for glaucoma. Laser surgery for glaucoma can increases the outflow of the fluid from the eye in open-angle glaucoma or eliminates fluid blockage in angle-closure glaucoma. Types of laser surgery for glaucoma include trabeculoplasty (SLT or ALT), in which a laser is used to create openings in the trabecular meshwork drainage area; iridotomy, in which a tiny hole is made in the iris, allowing the iris to move away from the drainage angle and for the fluid to flow more freely; and cyclophotocoagulation, in which a laser beam treats areas of the ciliary body, reducing its production of fluid.

Microsurgery for glaucoma. In an operation called a trabeculectomy, a new channel is created to drain or filter the fluid, thereby reducing intraocular pressure that causes glaucoma. Sometimes this form of glaucoma surgery fails and must be redone. For some patients, a glaucoma tube implant is the best option. Finally, newer procedures like canaloplasty are less invasive and carry less risk than traditional surgeries like trabeculectomy. In this procedure, Schlem’s canal is dilated witha viscoelastic gel and a stent is placed for 360 degrees into teh canal. Other complications of microsurgery for glaucoma include some temporary or permanent loss of vision, as well as bleeding or infection.