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Researchers supported by the National Institutes of Health have discovered that black and white patients with advanced glaucoma respond differently to two surgical treatments for the disease. A paper detailing these findings is published in the July 1998 issue of Ophthalmology.
Scientists found that blacks with advanced glaucoma benefit more from a regimen that begins with laser surgery, and whites benefit more from one that begins with an operation called a trabeculectomy.
“This is the first evidence that members of two racial groups benefit from different treatments for glaucoma,” said Carl Kupfer, MD, director of the National Eye Institute (NEI), one of the Federal government’s National Institutes of Health and the sponsor of the study. “Doctors now have better information to recommend treatment programs, depending on the patient’s race. This will give people with advanced glaucoma a better chance to preserve and prolong their vision.”
A leading cause of irreversible vision loss in the United States, glaucoma affects about three million Americans, about half of whom maybe unaware they have the disease because of its lack of earlysymptoms. The disease is three to four times as common in blacks as inwhites, and blindness from glaucoma is six times as common in blacksthan in whites.
Glaucoma is a group of diseases that damages the eye’s opticnerve and can lead to blindness. It tends to worsen over time.Open-angle glaucoma, the most common form and the one examined in thisstudy, usually occurs when the normal fluid pressure inside the eyeprogressively increases. This increased pressure can lead to opticnerve damage and reduced peripheral (side) vision. As the diseaseworsens, the field of vision gradually narrows and blindness mayresult.
Treatment aimed at lowering the pressure within the eye is believedto slow progression of the disease. In its early stages, glaucoma isusually treated with daily eye drops. In some patients, the beneficialeffect of the eye drops wears off with time, and “advancedglaucoma” develops. At this point, doctors usually recommendlaser surgery, irrespective of race, and supplement it with eye dropsas needed. If the beneficial effect of the laser surgery wears off,doctors usually recommend a trabeculectomy, and, if its effect wearsoff, a second trabeculectomy.
The major purpose of the study, called the Advanced GlaucomaIntervention Study (AGIS), was to find out which of two advancedglaucoma treatment regimens better preserves vision. Over a four-yearperiod, researchers enrolled 332 black patients (451 eyes), and 249white patients (325 eyes). All eyes involved in the AGIS had advancedglaucoma. The patients’ eyes were assigned randomly to one of twotreatment regimens: one beginning with laser surgery, the otherbeginning with the trabeculectomy surgery.
After seven years of follow-up on these patients, the study resultsrevealed that blacks and whites differed in the way they benefitedfrom the two treatment programs. More specifically:
- The vision in eyes of black patients with advanced glaucomatended to be better preserved in the program that started with thelaser surgery. From initial treatment through seven years offollow-up, the average percent of eyes in black patients withdecrease of vision was 28 percent in the program starting with lasersurgery, as compared with 37 percent in the program starting with atrabeculectomy.
- Through the first four years, the vision in eyes of whitepatients with advanced glaucoma tended to be better preserved in theprogram starting with laser surgery. Thereafter, however, thereverse was true; seven years after the initial treatment, theaverage percent of eyes in white patients with decrease of visionwas 31 percent in the program starting with a trabeculectomy, ascompared with 35 percent in the program starting with laser surgery.
“Based on the study results, it is recommended thatblack patients with advanced glaucoma begin a treatment program thatstarts with laser surgery, which is consistent with current medicalpractice,” said study co-chairman Douglas E. Gaasterland, MD, ofGeorgetown University. “In contrast, white patients with advancedglaucoma who have no life-threatening health problems should begin atreatment program that starts with trabeculectomy. This recommendationis inconsistent with current medical practice.”
Dr. Gaasterland also said that it is “important to note thatnot all patients responded to the treatments in the same way. Thevision of most, but not all, black patients was better preserved iftheir program started with laser surgery. Four years after the firstsurgical treatment of white patients, the vision of most, but not all,was preserved better if their program started with trabeculectomy.”
Because glaucoma is a life-long disease, long-term information isimportant. The AGIS patients will continue to be followed for up tofour more years.
The Advanced Glaucoma Intervention Study is being conducted in 12medical centers and affiliated doctors’ offices in the UnitedStates. A list of the study centers is attached.
The National Eye Institute, part of the National Institutes ofHealth, is the Federal government’s lead agency for vision research,and supports between 70 to 80 percent of basic and applied visionresearch in the United States.
The Advanced Glaucoma Intervention Study (AGIS)
Glaucoma, called the “thief of vision” because of its lackof early symptoms, is a leading cause of irreversible vision loss inthe United States and affects an estimated three million Americans. Itis estimated that as many as 120,000 Americans are now blind from thedisease.
In normal vision, a clear fluid flows continuously in and out of aspace in the front of the eye called the anterior chamber. This fluidnourishes nearby tissues. The fluid leaves the anterior chamber at theangle where the iris and cornea meet. When the fluid reaches this openangle, it flows through a spongy meshwork, like a drain, and leavesthe eye. Open-angle glaucoma gets its name because for unknownreasons, the fluid passes too slowly through the meshwork drain. Asthe fluid builds up, the pressure inside the eye rises. Unless thepressure at the front of the eye is controlled, it can damage theoptic nerve and cause vision loss.
Groups at high risk of developing the disease are everyone over theage of 60, blacks over the age of 40, and people who have a familyhistory of glaucoma. The Baltimore Eye Survey, supported by theNational Eye Institute, shows that by age 70, about one in 50 whiteshas the disease. In blacks, the problem is more severe by age70, one in eight has the disease. Open-angle glaucoma tends to developearlier in blacks than in whites, and progresses more rapidly.
It is believed that early treatment can substantially reduce thelikelihood of severe vision loss or blindness. However, many people athigh risk for blindness from glaucoma are unaware of the importance ofearly detection, or are not having their eyes examined on a regularbasis for the disease. Increased public awareness of the potentialbenefits of a regular, comprehensive eye examination with dilatedpupils may serve to reduce the enormous social and personal costs ofopen-angle glaucoma.
About the Advanced Glaucoma Intervention Study
The Advanced Glaucoma Intervention Study (AGIS) is a randomizedclinical trial designed to determine which of two advanced glaucomasurgical treatment programs one beginning with laser surgery,the other beginning with an operation called trabeculectomy (seefigure) better preserves vision. The study is being conductedin 12 medical centers and affiliated doctors’ offices in theUnited States.
Laser surgery for glaucoma involves using a high energy beam of light to make 50-100 evenly-spaced burns in the meshwork inside theeye. These tiny burns open up the drainage area, allowing for betteroutflow of the fluid. This procedure, often done in the doctor’soffice, requires only local anesthesia. In a trabeculectomy procedure,a small opening is made in the front chamber of the eye, providing anew drainage pathway for the fluid inside the eye. This procedure,done in an operating room, requires local or general anesthesia.
Researchers followed patients for seven years after their initialsurgery for advanced glaucoma. In 28 percent of the cases, thebeneficial effect of the initial surgical treatment (either the lasersurgery or the trabeculectomy) wore off. When this happened, eyes weretreated according to their study protocol assignment, as follows:
- If the treatment beginning with the trabeculectomy lost itseffect, patients’ eyes would then receive the laser surgery.If, in these eyes, the laser surgery lost its effect, the eyes wouldreceive a second trabeculectomy.
- If the treatment beginning with the laser surgery lost itseffect, patients’ eyes would then receive the trabeculectomysurgery. If, in these eyes, the trabeculectomy lost its effect, theeyes would receive a second trabeculectomy.
After seven years of follow-up on these patients, the study results revealed that blacks and whites differed in the way they benefited from the two treatment programs.
Study investigators also observed that cataract operations were performed in a somewhat larger fraction of eyes that initially received trabeculectomy than in those that initially received laser surgery. Further, on the average, more supplemental medications were needed to control glaucoma in eyes that initially received laser surgery than in those that initially received trabeculectomy.
About the National Eye Health Education Program
As part of its mission to address glaucoma as a public health problem, the National Eye Institute has established the National Eye Health Education Program (NEHEP). The NEHEP is coordinated by the NEI in partnership with more than 50 public and private organizations whoplan and implement eye health education programs targeted to a varietyof high-risk audiences. The focus of the NEHEP is on public andprofessional education programs that encourage early detection andtimely treatment of glaucoma and diabetic eye disease.
As part of the NEHEP, the National Eye Institute, along with 25 other eye care organizations, annually promotes Glaucoma Awareness Month in January. This public service campaign highlights the importance of eye care and good vision, and urges those people at high risk for glaucoma to have a dilated eye exam at least every two years.
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- The Advanced Glaucoma Intervention Study (AGIS): 3. Baseline Characteristics of Black and White Patients. Ophthalmology. 1998 Jul. PubMed
- The Advanced Glaucoma Intervention Study (AGIS): 4. Comparison of Treatment Outcomes Within Race. Seven-Year Results. Ophthalomology. 1998 Jul. PubMed