GLAUCOMA RESEARCH FOUNDATION
From
1997 to 1998, I was the Managing Editor of the Glaucoma Research
Foundation’s quarterly newsletter, “Gleams”.
This work involved extensive online research and consulting with top
members of the ophthalmic research community.
TABLE OF CONTENTS
To Treat or Not to Treat
The Ocular Hypertension Treatment Study
A New Look At
Normal Pressure Glaucoma
Glaucoma Surgical Outcomes Study
Two New Glaucoma Medications
The Wick Procedure
Facts About: Glaucoma and Cataracts
Facts About: Filtering Microsurgery
Facts About: Laser Surgery
Many people believe that high intraocular pressure (IOP) always leads
to the development of glaucoma. Actually, there are many people who have higher
than normal IOP and don't show any evidence of optic nerve or visual field
damage, the hallmark of glaucoma. This is a condition called 'ocular
hypertension' which is the subject of a major research study supported by the National
Eye Institute.
The relationship between ocular hypertension and glaucoma is still
uncertain. It is estimated that between 3 and 8% of Americans have ocular
hypertension and are considered to be at increased risk for glaucoma. In
addition, ocular hypertension is eight to ten times more common than primary
open-angle glaucoma. In 1969, Dr. Mansour Armaly reported that those who had
ocular hypertension, but did not show any signs of glaucoma, outnumbered
glaucoma patients about 10 to 1. Of those who are ocular hypertensive, between
0.5 to 1% will develop glaucoma each year. After 20 years, roughly 34% of those
who started with ocular hypertension will go on to develop glaucoma. The
question remains, should doctors treat ocular hypertensive people as if they
had glaucoma?
In order to answer this question, the National Eye Institute organized
the Ocular Hypertension Treatment Study (OHTS) in 1994. This study hopes to
determine whether using medicine to lower the intraocular pressure of those
with ocular hypertension will prevent or delay optic nerve damage due to
glaucoma.
Since the OHTS started, over 1,600 people at 21 clinical centers
nationwide have volunteered to participate in this ten year study. Only those who have ocular hypertension and
were diagnosed as having a moderate risk of developing open-angle glaucoma were
enrolled in the study. The study will compare those who received medication for
their elevated IOP to those receiving careful follow-up without medication
treatment.
Once concluded, the OHTS promises to be an important study that will
either support the treatment of ocular hypertensive people with medication or
allow physicians to feel more comfortable not treating these patients unless
they show early evidence of pressure-related glaucoma damage.
Until research finds the most effective way to treat ocular
hypertension, it is important to establish a working dialogue with your doctor
to determine the best strategy for you.
A New Look At Normal Pressure Glaucoma
It is estimated that normal pressure glaucoma (NPG) affects
about 20% of people who have glaucoma. NPG, also called normal tension glaucoma
or low tension glaucoma, can cause visual loss and damage to the optic nerve
even though pressure levels in the eye stay in the "normal" range.
Dr. Martin Wax and his colleagues at Washington University in
St. Louis, Missouri, are taking an interesting approach in their study of NPG.
They are investigating the idea that in some patients, NPG may be an autoimmune
disease. An autoimmune disease occurs when the antibodies of the immune
system-- which usually protect the body-- turn against it. The production of
antibodies to the body's own proteins is often normal. However, when an
individual's antibodies turn and react abnormally with the body's own proteins,
in many cases, the system goes awry and disease results. Other examples in which abnormal antibody
production has been shown to cause disease include myasthenia gravis, juvenile
diabetes and rheumatoid arthritis.
The study found that some NPG patients have higher blood levels
of certain specific antibodies, in comparison to non-glaucoma or high-pressure
glaucoma patients of the same age. The researchers are now focused at trying to
identify which proteins in the eye's retina are targeted by these abnormal
antibodies. More importantly, they hope to understand how these antibodies
interfere with the visual function of the retina and/or the optic nerve
proteins to which they bind. Dr. Wax believes that antibody disruption of the
optic nerve function may cause vision loss in-patients who have an autoimmune
form of NPG.
By identifying the specific antibodies that play a role in NPG,
then different immuno-suppressive drugs, which target individual antibodies,
might be used to combat the disease. Dr. Wax and his team are currently testing
such drugs on NPG patients. In the future, these antibodies may also act as a
signal to doctors, allowing them to prescribe preventive treatment, before
vision loss has a chance to begin.
Glaucoma filtration surgery (trabeculectomy) has prevented
vision loss in tens of thousands of glaucoma patients over the years. However, like all surgery, it may have
complications. The most serious complication of glaucoma filtration surgery is
the development of an infection within the eyeball itself. These infections are rare. It is estimated
that 0.2% of those who have filtering surgery per year go on to develop surgery
related eye infections.
Filtration surgery allows fluid to flow out of the eye, helping
to lower the intraocular pressure. This also reduces the eye’s defenses against
infection. In a normal, unoperated eye,
"pink eye" or conjunctivitis is nothing more than an uncomfortable
nuisance. In an eye that has undergone glaucoma surgery, "pink eye"
can produce a serious infection.
Many glaucoma specialists believe that infection after glaucoma
surgery is becoming more and more common. The Glaucoma Surgical Outcomes Study
(SOS), was designed to determine what factors may cause the development of
serious infections after filtration surgery. Upon completion, this study,
funded entirely by the Glaucoma Research Foundation, will help doctors and
patients take steps to further reduce the risk of an infection after surgery.
Drs. Henry Jampel and Harry Quigley and their associates visited
10 busy glaucoma practices and reviewed records of patients who developed
infections after surgery. They also reviewed records of patients operated on by
the same surgeon at about the same time who did not develop an infection.
Comparing the characteristics of patients with and without infections
identified risk factors for the development of an infection.
It was discovered that age, gender and race were not important
factors in determining whether or not a person would develop an infection. How
the operation and the post-surgery procedures were performed seemed
significant. Risk factors for infection included the use of drugs that reduc e
scarring and the location of the incision.
After surgery, leakage was a risk factor. One unique finding was that
the use of antibiotics for prolonged periods after surgery appeared to
increase, rather than decrease, the risk of infection.
Armed with these results, glaucoma surgeons for the first time
will be able to rationally consider the risk of infection when recommending
glaucoma surgery and when determining how to perform the operation.
Post-surgery monitoring of the surgical site by both doctor and patient can
help prevent infection. Although not directly addressed in the glaucoma SOS, it
is clear that the sooner an early infection is detected, the easier it is to
treat, and the better the outcome. For this reason, patients who have had
glaucoma filtration surgery need to treat the development of a red, irritated
eye (particularly if there is a discharge or a decrease in vision) as a
possible emergency.
The FDA has recently approved two new glaucoma medications,
Cosopt, developed by Merck & Co., Inc. and Azopt, from Alcon Laboratories,
Inc.
Glaucoma is a chronic condition and many people use multiple
medications to control their disease. It is estimated that more than half of
all those being treated for glaucoma currently take more than one topical
medication to control their eye pressure. Simplifying multiple drug regimens
can increase the success of the overall treatment.
Cosopt is the first eye drop that combines a topical carbonic
anhydrase inhibitor (Trusopt) and a topical beta-blocker (Timoptic), both
designed to decrease the production of intraocular fluid. By combining both
Trusopt and Timoptic, Cosopt offers an effective and hopefully simpler use of
topical medication. Cosopt reduces intraocular pressure (IOP) in those with
open-angle glaucoma by reducing the secretion of fluids inside the eye. In
clinical studies, Cosopt administered twice a day was more successful in
reducing IOP than treatments using only Trusopt or Timoptic. However, a daily
regimen of both Trusopt (3 times a day) and Timoptic (2 times a day) was shown
to have lowered IOP slightly more than just Cosopt.
Cosopt’s most frequently reported side effects are burning
and/or stinging of the eyes, and changes in taste, in up to 30% of those
studied. Five percent discontinued using Cosopt as a result of adverse effects.
Cosopt will not be prescribed to those with a history of bronchial asthma,
severe chronic obstructive pulmonary disorders, certain heart conditions or if
a person demonstrates hypersensitivity to any component of the product.
A new carbonic anhydrase inhibitor (CAI) called Azopt, from
Alcon Laboratories, Inc., has just been approved. Topical CAI’s lower
intraocular pressure (IOP) by reducing the production of aqueous humor, the
clear fluid that flows through the eye.
Currently, the two other topical CAI’s on the market are Trusopt
and Cosopt. However, Azopt has a pH similar to human tears, which may make it
more comfortable to use. In two clinical studies, four times the number of
glaucoma patients experienced burning and stinging with another CAI than with
Azopt. It can lso be prescribed with other eye drops used to control glaucoma.
Azopt's listed side effects are eye irritation, burning,
conjunctivitis, inflammation and itching. Some people experienced a bitter
taste right after using Azopt. These effects may diminish with time. Azopt is
related to the sulfa drugs so those with sulfa allergies will be allergic to it
as well.
Please consult with your doctor to determine if Cosopt or Azopt
are appropriate for your glaucoma treatment.
Can implanting a strip of collagen called a wick be a safer form
of glaucoma surgery? Wick manufacturer STAAR Surgical believes that the
collagen strip offers an effective alternative to standard glaucoma surgery.
In standard glaucoma filtration surgery, surgeons create a flap
in the sclera, which is reflected back towards the cornea. A hole is made
directly in the anterior chamber of the eye, the space between the cornea and
the iris. The scleral flap is then placed back in position and covered by the
conjunctiva, the skin covering the white part of the eye. This provides for a
fluid flow out of the eye.
One of the difficulties with standard filtration surgery is that
the pressure in the eye may drop very low for a few days after surgery.
Complications and side effects can occur because of this low pressure. These
may include bleeding within the eye, damage to the cornea, and sometimes
scarring and loss of the anterior chambers (the front of the eye).
Instead of making a complete hole in the anterior chamber, the
wick surgery involves making a small incision to the trabecular meshwork (the
spongy area of tissue by the iris and sclera). Once the fluid flow appears to
be sufficient, the wick is placed.
The wick is about ¾ of an inch long and the width of a pencil
lead. Once it is implanted, it is believed to expand, then dissolve over
several months, providing a channel for fluid flow.
Currently, the wick procedure is in clinical trials at ten
centers in the U.S. Gleams will keep readers updated with significant findings
as they become available. If you would like more information, contact STAAR at:
STAAR Surgical Company, 1911 Walker Ave., Monrovia, CA 91016
Facts About: GLAUCOMA & CATARACTS
What is glaucoma? What is cataract?
Glaucoma
is a group of eye diseases that involve damage to the optic nerve. Common
features of glaucoma can include too much fluid pressure in the eye, damage in
the optic nerve area and visual field (sight) loss. A cataract is an eye
condition where cloudiness, or opacity in the lens, blocks or changes the entry
of light, affecting vision.
Are those with glaucoma at higher risk to develop
cataracts?
Those
with glaucoma are usually not at higher risk to develop cataracts. There are
exceptions, and they include those who have glaucoma due to secondary causes
such as eye inflammation, eye trauma, or steroids. Also at higher risk are
those with developmental conditions, such as congenital rubella, which can
cause glaucoma, cataracts, or sometimes both. Both eye conditions are also more
common with age, which is why many who have one disease may develop the other.
Can surgery restore vision loss from a cataract?
Unlike
vision loss from glaucoma, cataract vision loss can often be regained. In most
cases of cataract surgery, the cloudy lens of the eyes is removed and replaced
with a clear plastic lens (called intraocular lens implant). The process of
removing a cataract is called extracapsular lens extraction. After this
process, an outer membrane lens capsule often remains. This membrane can slowly
thicken and cloud vision. A laser procedure (called a capsulotomy) can open
this membrane, restoring clear vision without the standard cutting procedure.
When is cataract surgery needed?
Cataract
surgery is suggested when a person's vision has declined to the point where it
interferes with their usual daily tasks. If a cataract develops in a part of
the eye lens where it does not affect vision, cataract surgery may never be
needed.
How will cataract surgery affect the glaucoma?
Cataract
surgery can cause a change in the eye's pressure. This change may be short-term
or permanent. In general, it is not possible to predict whether the IOP will
rise, fall or stay the same after cataract surgery. Sharp increases in eye
pressure are called "pressure spikes" and sometimes occur in patients
after cataract surgery. Often these pressure spikes are short-term and can be
treated with medicines.
If both glaucoma surgery and cataract surgery are
needed, can the two procedures be combined?
The
first priority is to control the person's glaucoma. A person may have a
glaucoma procedure followed by cataract surgery, or have both surgeries done at
the same time. The specific approach
will depend on the medical needs of the person with glaucoma.
How do cataracts and glaucoma medicines interact?
Those
who have glaucoma and use adrenergic agonist medicines, such as epinephrine or
Propine may notice an increase in glare, if they have a cataract. This is
because these eye drops may make the pupil larger and can expose the cataract
to more light. Others who use miotic eye drops, such as pilocarpine or
carbachol, for intraocular ressure (IOP) control may find their vision lowered
by the glaucoma medicines. These medicines tend to shrink the pupil, which
lowers the amount of light entering the eyes.
Since cataracts may already be clouding vision, this may make vision
worse. Those who have either of these problems may wish to talk to their doctor
about possible treatment options, such as other medicines, laser treatment, or
surgery.
Can medicine treat cataracts?
There
are no current medicines that have been proven to be helpful in the treatment
of cataracts.
Facts About: FILTERING MICROSURGERY
What is filtering microsurgery?
In
glaucoma, the eye's inner fluid pressure can build up and damage the optic
nerve, the nerve that carries visual pictures to the brain. Damage to the optic
nerve can lead to vision loss. When medicines and laser surgeries do not lower
pressure enough, eye doctors may recommend a procedure called filtering
microsurgery (sometimes called conventional or cutting surgery). In filtering
microsurgery, a tiny drainage hole is made in the sclera (the white part of the
eye) in a procedure called a trabeculectomy or a sclerostomy. The new drainage hole
allows fluid to flow out of the eye and helps lower the eye pressure. This
prevents or reduces damage to the optic nerve.
Is there pain during the microsurgery?
In
most cases, there is no pain involved. The surgery is usually done with local
anesthetics and relaxing medications. Often a limited type of anesthesia,
called intravenous (I.V.) sedation, is used. In addition, an injection is given
around or behind the eye to prevent eye movement. This injection is not painful
when I.V. sedation is used first. The patient will be relaxed and drowsy and
will not experience any pain during surgery.
How does the eye doctor determine if filtering
surgery is needed?
Often,
laser surgery is recommended before filtering microsurgery, unless the eye
pressure is very high or the optic nerve is badly damaged. During laser
surgery, a tiny but powerful beam of light, is used to make severeal small
scars in the eye's trabecular meshwork (the eye's drainage system). The scars
will help increase the flow of fluid out of the eye. In contrast, filtering
microsurgery involves creating a drainage hole with the use of a small surgical
tool. When laser surgery does not successfully lower eye pressure or the
pressure lowering effects wear off, the doctor may recommend filtering microsurgery.
What is the success rate?
Most
of the related studies document follow-up for a one year period. In those
reports, it shows that in older patients, glaucoma filtering surgery is
successful in about 70-90% of cases, for at least one year. Occasionally, the
surgically created drainage hole begins to close and the pressure rises again.
This happens because the body tries to heal the new opening in the eye, as if
the opening were an injury. This rapid healing occurs most often in younger
people, because they have a stronger healing system. Anti-wound healing drugs,
such as mitomycin-C and 5-FU help slow down the healing of the opening. If
needed, glaucoma filtering surgery can be done a number of times in the same
eye.
Is this an outpatient procedure or is an overnight
stay in the hospital needed?
Usually,
filtering surgery is an outpatient procedure, requiring no overnight hospital
stay. Within a few days after surgery, the eye doctor will need to check on the
eye pressure. The doctor will also look for any signs of infection or increase
in inflammation.
How long is the recovery time?
For
at least one week after surgery, patients are advised to keep water out of the
eye. Most daily activities can be done, however, it is important to avoid
driving, reading, bending, and doing any heavy lifting. Since each case is
different, patients should check with their doctor for specific advice.
How
will the eye look after surgery? Is there a noticeable scar or redness?
The
eye will be red and irritated shortly after surgery, and there may be increased
eye tearing or watering. The inner eye fluid flows through the
surgically-created hole and forms a small blister-like bump called a bleb. The
bleb, usually located on the upper surface of the eye, is covered by the
eyelid, and is usually not visible.
Will vision be changed? Will glaucoma medications
still need to be taken?
There
may be some vision changes, such as blurred vision, for about six weeks after
the surgery. After that time, vision will usually return to the same level it
was before surgery. Vision can sometimes improve after surgery in people who
were previously using pilocarpine. When pilocarpine drops are no longer taken,
the pupil returns to normal size, allowing more light to enter the eye. In a few
cases, the vision may be worse due to very low pressure. Cataracts or wrinkle
in the macula area of the eye may develop. In terms of vision correction, a
patient's glasses or contact lenses may need to be changed after surgery. Both
gas permeable and soft contact lenses may be worn after glaucoma filtering
surgery. There may be fitting problems due to the bleb. Special care is needed
to avoid infection of the bleb. Contact lens users should discuss these
problems with their eye doctor following surgery.
What is laser surgery?
Laser
surgeries have become important in the treatment of different eye problems and
diseases. In laser surgery, a laser is a small but powerful beam of light that
can make a small burn or opening in the eye's tissue. During the laser surgery,
the eye is numbed so that there will be little or no pain. The eye doctor will
then hold a special lens to the eye. The laser beam will be aimed into the eye,
and a bright light- like a camera flash- will be seen.
Are
there risks associated with glaucoma laser surgeries?
Laser
surgery is still surgery, and can carry some risks. Some people experience a
short-term increase in their intraocular pressure (IOP) soon after surgery. In
others who require YAG CP (Cyclophoto-Coagulation) surgery, there is a risk of
the IOP dropping too low to maintain the eye's normal metabolism and shape. But
the use of anti-glaucoma medication before and after surgery can help to reduce
this risk.
What
are the different laser surgeries used in glaucoma?
The
type of laser surgery used will depend on the type of glaucoma and the general
health of the eye. The most common glaucoma laser surgeries are:
Laser Peripheral Iridotomy (LPI):
Often used in people with narrow-angle glaucoma.
Narrow-angle glaucoma occurs when the angle between the iris and the cornea in
the eye is too small. This causes the iris to block the fluid drains, which
makes the inner eye pressure increase. The LPI makes a small hole in the iris,
so the iris falls back from the fluid channel, helping the fluid drain.
Argon Laser Trabeculoplasty (ALT)
Used in people with primary open angle glaucoma (POAG). The
laser beam opens the fluid channels of the eye, helping the drainage system to
work better. In many cases, medication
will still be needed. It has successfully lowered the eye pressure in up to 75%
of patients treated.
Nd:YAG Laser Cyclophoto-coagulation
(YAG CP)
Used in people with severe glaucoma damage that is not being
managed by standard glaucoma surgery.
Is there pain or discomfort with glaucoma laser
surgery?
There
is a slight stinging sensation associated with LPI and ALT. In YAG CP laser
surgery, a local anesthetic is used to numb the eye. Once the eye has been
numbed, there should be little or no pain and discomfort. What are the
long-term benefits of having glaucoma laser surgery? Will a repeat procedure be needed? Glaucoma laser surgeries help
to lower the IOP in the eye. The length of time the IOP is lowered will depend
on the type of laser surgery, the type of glaucoma, age, race, and many other
factors. Some people may need the surgery repeated to get better control of the
IOP, depending on the type of laser surgery done.
Is it common to have laser surgery over two
sessions?
For
people requiring ALT surgery, half of the fluid channels are usually treated
first. Depending on the person's eye, the other fluid channels can be treated
at a different time. This method prevents over-correction and lowers the risk
of an increased IOP after the surgery.
Will laser surgery eliminate the need for
medications?
In
most cases, medications will still be necessary to control and maintain eye
pressure. However, surgery may lessen the amount of medication needed.
How much recovery time is needed after laser
surgery?
Laser
surgery is usually performed in an eye doctor's office or eye clinic. Before
the surgery, the eye will be numbed by medicine. The eye may be a bit irritated
and vision may be slightly blurry after laser surgery. A ride home on the day
of the surgery should be arranged. In general, patients can resume their normal
daily activities the day after the surgery. But it is important to discuss any
questions or concerns about laser surgery with the eye doctor.
Does glaucoma laser surgery increase the risk for
developing cataracts?
There
is a small risk of developing cataracts after some types of laser surgery for
glaucoma. However, the potential benefits of the surgery usually outweigh any
risks. There is a common myth that lasers can be used to remove cataracts; this
is not the case except in experimental studies. After a cataract has been taken
out with conventional cutting surgery, there often remains an outer membrane
lens capsule. This membrane can slowly thicken and cloud vision, just as the
cataract did. Laser surgery can open this membrane, helping to clear vision
without an operation. This laser procedure is called a capsulotomy.
