Results of five-year, multi-site study prove safety
and efficacy of topical medication
(Philadelphia,
PA) -- Open-angle glaucoma -- the most common form of
glaucoma -- is a leading cause of blindness in the United
States and the number one cause of blindness in African
Americans, affecting more than 2.2 million Americans
age 40 and over. It occurs when the optic nerve is damaged;
damage which, in most cases, is caused by elevated pressure
in the eye.
However, not everyone with elevated pressure develops
glaucoma and there are some who develop the disease
despite having normal eye pressure.
Now, researchers at Scheie Eye Institute at the
University of Pennsylvania School of Medicine,
led by Jody Piltz-Seymour, MD, have determined
that eye drops used to treat elevated pressure inside
the eye can be effective in delaying -- and possibly
preventing -- the onset of glaucoma. The results of
the five-year, 22-site nationwide Ocular Hypertension
Treatment Study (OHTS) appear in the June issue of the
Archives of Ophthalmology.
The randomized study, which enrolled 1636 patients --
25% of whom were African Americans -- was designed to
determine the safety and effectiveness of eye drops
that lower eye pressure in preventing or delaying the
onset of primary open-angle glaucoma in people with
elevated pressure but no evidence of glaucoma damage.
The participants were divided into two groups -- one
group received the eye drops, the second group received
no medication but was observed throughout the duration
of the study.
According to Dr. Piltz-Seymour, principal investigator
of the study at the Penn site, the rate of developing
glaucoma in OHTS was reduced by more than 50% in participants
who were administered the eye drops.
Overall, 4.4% of the study participants who received
the eye drops developed glaucoma within five years,
compared to 9.5% of the study participants who did not
receive the eye drops. "It is estimated that between
three and six million people in the United States have
elevated eye pressure, which increases their risk for
developing this common form of glaucoma," explains
Dr. Piltz-Seymour. "Until now, we did not know
if treating elevated eye pressure -- before glaucoma
developed -- could delay the onset of the disease. The
results of the OHTS show us that, for some of the affected
population, pressure-lowering drops are beneficial."
Dr. Piltz-Seymour cautioned, however, that not all people
with elevated eye pressure require treatment.
"While OHTS clearly showed a protective effect
of treatment, it is important to remember that 90% of
the participants in the observation (no eye drop) group
did not develop glaucoma within the five-year study
period.
When deciding when to treat, doctors and patients need
to work together to evaluate the person's risk of developing
glaucoma, their overall health and life expectancy,
as well as the cost, inconvenience, and possible side
effects of this treatment."
The study also showed that treatment of elevated eye
pressure with eye drops had a very low incidence of
side effects.
A third item that the study emphasized was the importance
of corneal thickness measurement -- a procedure only
recently recognized as important in evaluating a person
for glaucoma. Researchers have identified that the accuracy
of eye pressure readings can be influenced by the thickness
of the cornea -- the front window of the eye. Thick
corneas cause eye pressure readings to be higher than
true pressure, while thin corneas cause pressure under-estimations.
In the OHTS, eye with thinner corneas were found to
be more at risk for the development of glaucoma, most
likely because this group had higher eye pressures than
were actually measured.
In addition to thin corneas, several other risk factors
were found to be associated with the development of
glaucoma in study participants. These included personal
risk factors, such as older age and African descent,
as well as ocular risk factors, such as higher eye pressure
and certain characteristics in the anatomy of the optic
nerve.
The Ocular Hypertension Treatment Study was sponsored
by the National Eye Institute (NEI), one of the federal
government's National Institutes of Health, the National
Center on Minority Health and Health Disparities, Research
to Prevent Blindness and Merck Research Laboratories.
# # #
Editor's note:
Dr Piltz-Seymour does not have any financial interest
in Merck Research Laboratories. Researchers were permitted
to use an FDA-approved eye medication manufactured by
any company. All eye drops were supplied by the study
to the patient. Merck makes three medicated eye drops
-- Timoptic, Trusopt; and Cosopt.
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