Glaucoma

Glaucoma is a family of more than 30 diseases that affects pressure within the eye, damaging the optic nerve. When pressure inside the eye increases, blind spots in peripheral areas of vision may occur. Of all conditions and diseases of the eye, glaucoma is one of the leading causes of blindness in the United States. Often called the "sneak thief" of sight, most forms of glaucoma do not produce symptoms until vision is already severely damaged. But if diagnosed early, the disease can be controlled and permanent vision loss can be prevented.

Bascom Palmer Eye Institute is fully committed to research, diagnosis, and treatment of glaucoma. With seven glaucoma specialists in the Department of Ophthalmology at the University of Miami Miller School of Medicine, Bascom Palmer is a leader in research, as well as the clinical care of patients with glaucoma.

What are the common types of glaucoma?

• Acute Angle Closure Glaucoma: acute closure of the peripheral drainage angle, characterized by a sudden increase in intraocular pressure.
• Chronic Angle Closure Glaucoma: the iris obstructs the eye's drainage angle in a slow, progressive fashion.
• Primary Open Angle Glaucoma: the drainage angle is open but does not allow fluid to drain adequately for unknown reasons.
• Pseudoexfoliation Glaucoma: deposits of a fibrillary material obstruct drainage of fluid from the eye.
• Pigmentary Glaucoma: pigment dislodged from the iris obstructs the eye's drainage structures.
• Angle Recession Glaucoma: scar tissue from previous trauma obstructs the outflow of fluid.
• Neovascular Glaucoma: various disorders cause blood vessels to proliferate on the iris and in the eye's drainage structures.
• Congenital Glaucoma: the eye's drainage channels form abnormally during gestation.

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What are the risk factors for glaucoma?

Although glaucoma is most common in adults over the age of 40, susceptibility is not determined by age alone. There is a genetic component, and those with a family history of the disease, as well as African-Americans, are at increased risk. Those with hypertension, diabetes and other systemic diseases are also at risk. Studies have shown individuals at greater risk for glaucoma may fit one or more of the following criteria:

• are over the age of 60
• have a family history of the disease, elevated intraocular pressure
• are African-American over the age of 40
• have diabetes or hypertension
• are nearsighted

Since early detection is critical to avoiding permanent loss of vision, individuals who possess any of the non-age-related risk factors should have regular examinations by an ophthalmologist every one or two years.

Individuals in the general population should have a glaucoma evaluation every two or three years after the age of 40, and every one or two years after the age of 60.

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What is involved in a glaucoma evaluation at Bascom Palmer Eye Institute?

Bascom Palmer Eye Institute's specialists continuously fight the severe consequences of not detecting the disease in its early stages --- each year we treat nearly 40,000 patients who have advanced glaucoma. To achieve an accurate assessment, experienced ophthalmologists or optometrists perform a comprehensive glaucoma screening that consists of three non-invasive, pain-free procedures:

• Measurement of intraocular eye pressure (IOP). Elevated IOP is considered a major risk factor for the development of glaucoma. Studies have shown that optic nerve damage becomes more likely as the IOP increases.
  
  
• Assessment of the optic nerve. A non-invasive slit lamp biomicroscope is used to determine whether or not there are changes in the optic nerve in the diagnosis for glaucoma.
  

• Evaluation of a patient's visual field. Glaucomatous
  damage produces characteristic defects in the visual field.

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What is the treatment for glaucoma?

Glaucoma treatment seeks to decrease intraocular pressure and prevent damage to the optic nerve. Different types of glaucoma require different therapies to prevent further damage to the eye's structures. At the beginning of treatment, the doctor will generally recommend medication or a combination of medications for the specific condition. Therapies may include:

• Eye drops (or a combination of eye drops and pills) to reduce intraocular pressure. Several different classes of glaucoma medications are available to provide pressure reduction including beta blockers, prosaglandin analogues, alpha adrenergic agaonists, miotic, epinephrine compounds, and oral and topical carbonic anhydrase inhibitors. These medications work by either reducing the rate at which fluid in the eye is produced or increase the outflow of fluid from the eye.
• Laser treatment to open the drainage angle and reduce intraocular pressure.
• Surgery to create a new passage for fluid drainage. Surgery is usually reserved for cases that cannot be controlled by medication and following appropriate laser treatment.

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Frequently Asked Questions About Glaucoma

Is blindness due to glaucoma preventable?

Regular diagnostic examinations by an ophthalmologist are the key to preventing loss of vision due to glaucoma. Ophthalmologists are medical doctors, specialists in eye care and trained to examine and treat eye diseases. Although there is no way to reverse damage, if glaucoma is diagnosed and treated early, blindness almost always is preventable.

What are the symptoms of glaucoma?

Although the blindness associated with this disease is preventable, more than one million people in the United States have some glaucoma-related vision loss. In most cases, glaucoma is asymptomatic (has no symptoms). By the time an individual experiences decreased vision, the disease is frequently in its latter stages. Since early warning signs of glaucoma are rare, it is important --- especially for those at risk --- to have medical eye examinations at appropriate intervals, as described in this section.

Symptoms depend on the type of glaucoma the individual has.

• Those who have chronic glaucoma may not be aware of any symptoms because the disease develops slowly and patients rarely notice loss of peripheral vision.
  
  
• Those who have an acute form of glaucoma may develop severe symptoms because ocular pressure rises quickly and they may experience:
  • Blurred vision, especially at night
  • Halos or rainbows around lights
  • Severe headaches or eye pain
  • Nausea

How does glaucoma affect the eye?

The eye has an internal pressure created by production of a clear fluid called aqueous humor. This fluid circulates through the eye and exits through the anterior chamber angle and ultimately drains into the blood stream. In glaucoma, the aqueous humor outflow is obstructed, resulting in increased eye pressure and, eventually, optic nerve damage.

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Who are the glaucoma specialists at Bascom Palmer Eye Institute?

Douglas A. Anderson, M.D.
Donald Budenz, M.D., M.P.H.
Francisco Fantes, M.D.
Steven J. Gedde, M.D.
Alana Grajewski, M.D.
David S. Greenfield, M.D.
Elizabeth Hodapp, M.D.
Anna K. Junk, M.D.
Richard K. Lee, M.D., Ph.D.
Paul Palmberg, M.D., Ph.D.
Richard K. Parrish, II, M.D.
Carolyn Quinn, M.D.
Sarah Wellik, M.D.

What research is being conducted at Bascom Palmer for the management of glaucoma?

Tube Versus Trabeculectomy Study (TVT)
Bascom Palmer Eye Institute is one of the leading institutions (of fifteen participating centers) and is home to the Statistical Coordinating Center for the Tube Versus Trabeculectomy (TVT) Study. This study aims to improve our ability to care for glaucoma patients, and the results will guide us in recommending the best surgical procedures for our patients.

At present, two types of non-experimental glaucoma operations have been shown to be safe and effective surgical treatments. These procedures are known as tube shunt surgery and trabeculectomy.

Both tube shunt surgery and trabeculectomy lower the intraocular pressure by creating a route for aqueous fluid to drain out of the eye.

Tube shunts (such as the Baerveldt glaucoma implant) --- A tube inserted into the eye shunts aqueous fluid to a silicone plate that is attached to the sclera (the white portion of the eye).

Trabeculectomy --- A hole, surgically created under a trap-door incision in the sclera, allows aqueous fluid to drain. Mitomycin, an anti-scarring medicine, is commonly applied at the operation site to reduce scarring that could close the trap door.

Similar success and complication rates have been reported for both tube shunt surgery and trabeculectomy when each has been studied separately. It is unclear if one operation is superior to the other in safety and efficacy.

The TVT Study will examine the outcomes of a Baerveldt implant and trabeculectomy with Mitomycin C in patients who have had previous cataract surgery, glaucoma surgery, or a combination of both.

Ocular Hypertension Study
The Ocular Hypertension Study (OHTS) is a major clinical investigation now underway at medical centers nationwide, including Bascom Palmer Eye Institute. This study aims to determine whether it is better to treat patients as soon as they are diagnosed with elevated intraocular eye pressure (thought to be the leading risk factor for the development of glaucoma) who have no optic nerve damage or to delay treatment until ocular nerve damage begins.

The premise of OHTS is that high pressures may not lead to glaucoma. Researchers want to determine the risk factor for patients who have moderately elevated pressure, but normal optic nerves and visual fields.

Since only about one percent of patients per year who have elevated pressure and normal optic nerves and visual fields actually develop glaucoma, the critical issue is the identification of this small percentage. The National Eye Institute and the National Institutes of Health sponsor the significant work of the OHTS study.

In addition to evaluating the role of high intraocular pressure in the development of glaucoma, the OHTS study will address the following issues:

What factors affect drainage of the eye and subsequently cause increased pressure?

Is slightly elevated pressure normal in some patients?

What else may be involved in the optic nerve's response to increased pressure?

Are African-Americans at greater risk for glaucoma damage?

Retinal Nerve Fiber Layer
Physicians and scientists at Bascom Palmer are focusing on developing advanced technologies to diagnose glaucoma. For the past twelve years, we have studied the optical properties of the retinal nerve fiber layer (RNFL) to aid doctors who are using RNFL as a diagnostic method. While visual field tests have long been the primary method for detecting glaucoma, recent studies show that examinations applying new optical technologies reveal more definitive diagnostic RNFL information.

Since nerve fiber loss may be the earliest sign of glaucoma, it is important to obtain precise, quantitative information on the condition of the RNFL. Researchers are evaluating two new technologies --- scanning laser polarimetry and optical coherence tomography --- to enhance the quality and reproducibility of the diagnostic information obtained.

What research is being conducted in the United States for glaucoma patients?
Medical and surgical treatments are being researched in the United States. Multiple national clinical trials are ongoing examining the efficacy of different existing surgical and medical treatment modalities for glaucoma, including the Ocular Hypertension Study (OHTS), the Advanced Glaucoma Intervention Study (AGIS), the Collaborative Normal Tension Glaucoma Study (CNTGS), the Collaborative Initial Glaucoma Treatment Study (CIGTS) and the Tube Versus Trabeculectomy Study (TVT).

New medical treatments for glaucoma that affect blood flow to the optic nerve head, intraocular pressure, and survival of retinal ganglion cells are being investigated. Although decreasing intraocular pressure is the only treatment demonstrated to delay progression of most forms of glaucoma, neuroprotection to promote survival of the retinal ganglion cells either by preventing cell death (apoptosis) directly using apoptosis inhibitors or improving the cellular environment in the eye such as through blood flow regulation or addition of nerve cell growth factors are actively being tested. Combinations of different pre-existing glaucoma medications are in clinical trials examining their efficacy in studies sponsored mostly by the pharmaceutical industry.

Multiple technologies are being compared for the early detection of glaucoma including retinal nerve fiber and other structural analysis through scanning laser polarimetry, optical coherence tomography, scanning confocal microscopy, and ocular blood flow Doppler analysis. Different functional tests of retinal ganglion cell function including short wavelength automated perimetry (SWAP), frequency doubling time (FDT), and the pattern electroretinogram (PERG) are also actively being studied for early detection of visual field loss.

Surgical techniques such as selective laser trabeculoplasty (SLT) and non-penetrating types of filtering surgeries are being compared to conventional treatments such as argon laser trabeculoplasty, trabeculectomy and drainage implants. New glaucoma drainage implants that are possibly easier to implant or provide better pressure control are in the design and clinical trial phases of development.

Probably one of the most exciting areas of glaucoma research is in the area of genetics. Studies of families with glaucoma have identified several genes involved in glaucoma and the function of these genes and the search for more genes are ongoing. These studies will hopefully provide scientists with new targets to treat glaucoma in addition to intraocular pressure and possibly allow for genetic screening for patients at risk of developing glaucoma.

Pattern electroretinogram (PERG). The electroretinogram (ERG) for the eye can be thought of as being analogous to the electrocardiogram (EKG) for the heart. By studying the electrical activity pattern of the eye under different visual stimuli, scientists and clinicians at Bascom Palmer are designing new methods of diagnosing early glaucoma and for studying the progression of glaucoma.

Other Glaucoma Resources

American Academy of Ophthalmology
Eye Resources on the Internet
The Glaucoma Foundation
The Glaucoma Research Foundation
National Eye Institute
Research to Prevent Blindness

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