What is Glaucoma?

Glaucoma is a general term for a family of eye diseases, which, in most cases, lead to increased pressure within the eye and, as a result, damage the optic nerve.  The most common form, primary open angle glaucoma, initially causes painless loss of peripheral vision and may lead to blindness if untreated over many years.  Symptoms of a less common form, acute angle-closure glaucoma, may develop suddenly, accompanied by intense pain, and blindness may occur with a day or two if left untreated.

In general, glaucoma is more common in African-Americans and Hispanics, and the risk of developing glaucoma increases with age.  It is the second leading cause of blindness in all Americans and is generally accepted as an inherited disorder.

While glaucoma cannot be prevented, regular, complete eye examinations by an eye specialist can lead to early detection – and treatment often prevents loss of sight.

What Causes Glaucoma?

The underlying cause (or causes) of glaucoma remains unknown, although it is often accompanied by an increase of fluid pressure within the eye (called intraocular pressure).

The fluid within the eye, called the aqueous humor, nourishes the eye’s lens and cornea.  In healthy eyes, a pressure balance is maintained between the fluid that is produced by the ciliary body and the fluid that drains through specialized cells and tissue, called the trabecular meshwork.  If an injury or other factors affect this drainage area, disrupting the inflow/outflow balance, pressure can rise in the eye, which may eventually damage the optic nerce (the bundled nerve cells that transmit signals from the eye to the brain).

Not everyone with high intraocular pressure develops the disease and about one in five cases occurs in people with eye pressure that is within the normal range.  In every case, however, the result is optic nerve damage.  Research is steadily uncovering factors that contribute to optic nerve damage.

Types of Glaucoma

Primary open-angle glaucoma, the most common form of the disease, develops over time as the drainage angle tissue becomes clogged, causing the aqueous humor to drain too slowly and a gradual rise in intraocular pressure.  The risk of developing open-angle glaucoma increases with age.

Glaucoma in people with normal intraocular pressure is called normal tension, normal pressure or low-tension glaucoma.  It is not yet understood why glaucoma develops in people with normal intraocular pressure.

In angle-closure glaucoma, the outlet between the iris and cornea is not as wide and open as it should be and ultimately closes due to interference from the lens, which tends to grow larger as we age.  The resulting reduced flow of aqueous humor builds up pressure behind the iris and further reduces drainage through the trabecular meshwork, damaging the optic nerve.

If enough pressure builds behind the iris to force it against the trabecular meshwork, the fluid flow is suddenly blocked, causing a rapid and painful rise in eye pressure and an acute angle-closure glaucoma attack.  Acute-angle attacks can be triggered by darkened environments or stress, both of which cause the eye’s pupil to dilate, creating maximum contact between the lens and the iris.  Some medication can also cause acute angle-closure attacks.  Acute angle-closure glaucoma requires immediate medical attention.  If not corrected quickly, the elevated pressure can lead to permanent damage of the optic nerve.

Secondary glaucomas can appear as a complication of eye surgery or advance cataracts, or can result from eye injuries, certain eye tumors, or eye inflammation, Pigmentary glaucoma occurs when pigment from the iris flakes off and clogs the trabecular meshwork, Neovascular glaucoma is linked to diabetes.  Other, less common, types of glaucoma include juvenile open-angle glaucoma, congenital glaucoma, developmental glaucomas and pseudoexfoliation glaucoma.  Long-term use of certain steroid drugs can trigger glaucoma in genetically predisposed individuals. 

Symptoms

Open-angle glaucoma – The early stages of open-angle glaucoma are painless and vision is not affected.  As pressure continues to build within the eye over time, and the cells and nerve fibers that create the optic nerve die, “blind spots” form in the outer sides of the field of vision.  This loss of side vision may also go unnoticed unless detected by a detailed visual field examination.  As the disease progresses, the field of vision narrows.

Acute angle-closure glaucoma – Severe pain, reddened eyes, blurred vision, haloes around lights, headaches, nausea and vomiting can accompany acute angle-closure glaucoma.  A minor attack may involve painless blurred vision and haloes around lights.

Chronic angle-closure glaucoma – Symptoms of chronic angle-closure glaucoma may develop in a manner that is a combination of the two forms described above.  Symptoms may often be painless like open-angle glaucoma, but usually patients have brief episodes of blurry vision and discomfort that accompany intermittent attacks of angle closure.  Eventually, when the entire angle is closed from repeated brief attacks, high pressure may cause constant pain and visual blurring.  As in any form of glaucoma, long-term pressure elevation can ultimately lead to blindness.

How is Glaucoma Treated?

The goal in the treatment of glaucoma is to reduce the pressure in your eyes.  In acute glaucoma, immediate medical attention is needed.  Laser treatment is performed in the office to make an opening in the iris.  This will usually immediately lower the pressure.  However, if the pressure has been elevated too long, additional surgery or medications may be needed.

In primary open-angle glaucoma, the most common type, medications are used.  This involves taking eye drops daily to control the eye pressure.  Primary open angle glaucoma is a chronic disease and needs long-term treatment.  If medications are stopped or not used as directed, more damage will occur and visual loss will occur.  Selective Laser Trabeculoplasty (SLT) can also be used to lower the eye pressure.  This treatment acts as a medication to lower eye pressure.  It does not cure glaucoma and can be repeated.  (See section on SLT)

What types of medications are used to treat chronic open-angle glaucoma?

The first line treatment involves use of medication which are prostaglandin analogues:  Xalatan, Travatan or Lumigan.  These medications are similar and if your insurance coverage is better for one or the other, let us know and we can switch medication.  These medications are used once daily in the evening and increase outflow of aquous from the eye.  Side effects are rare and include redness, eye irritation and increased iris pigmentation.

Brimondine tartrate – Alphaghan and Alphagen P.  These medications are similar and can be interchanged.  They work by increasing outflow of aqueous humor from the eye and decreasing production of aqueous.  They are used twice per day and can be used with prostaglandin analogues.  Side effects can be common and include red eye, dry mouth, headaches, burning eyes and fatigue. 

Trusopt and Azopt are similar drops and act to reduce aqueous production.  They are used twice daily.  Both drops should not be used is there is a sulfa allergy.  Most common side effects are red eyes, dryness and tearing.

Beta blockers, Timolol and Betimolol are less expensive medications because they are generic; and they can be used once per day.  They do have serious side effects.  They lower cardiac output and also increase air pathway resistance.  They should not be used if you have asthma or COPD or heart disease.  If you do not have these conditions, these drugs are effective and can be used.

Cosopt is a combination of Trusopt and Timoptic.  This is a very effective medication.  It needs to be taken twice per day and you need to be able to take a beta-blocker.  

How do I know if my glaucoma is under control?
Sometimes it can be very difficult to know if glaucoma is under control.  There are usually no warning signs such as pain or blurred vision if the pressure is not low enough.  Vision loss occurs so gradually it can’t easily be detected by one’s self.  Once vision is lost, it cannot be recovered.

We rely on eye pressure measurement, corneal thickness measurement, visual field and optic nerve tomogram.  We check eye pressure at the office.  The eye pressure fluctuates daily, but we expect to see a normal range of pressure in the office.  We need to also measure your corneal thickness because, for example, a very thin cornea will give a false normal pressure reading.

We perform side vision testing at least once per year.     Glaucoma damages side vision before central vision.

We take a high resolution image of the optic nerve and can tell if more damage is occurring.  This is also done once per year.