Download New risk calculator helps physicians assess risk for glaucoma

EuroTimes 11-7
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3/7/06
2:26 pm
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Special Focus
New risk calculator helps physicians
assess risk for glaucoma
Robert Weinreb
Dermot McGrath
in Sao Paulo
A NEW tool designed to help assess the
risk of glaucoma in patients with ocular
hypertension and assist physicians in
deciding the best treatment strategy for
such patients was unveiled at the World
Congress of Ophthalmology.
The electronic risk calculator, developed
by Robert Weinreb MD and Felipe A
Medeiros MD, glaucoma specialists at the
Hamilton Glaucoma Center at the
University of California, San Diego, US,
represents the latest advancement in an
ongoing effort to create and introduce
predictive tools in ophthalmic medicine.
“The risk calculator helps to identify
patients with ocular hypertension who are
at high risk of developing glaucoma and
who may benefit from treatment, as well
as those who are at low risk who may not
need treatment. It will allow doctors to
assess patient risk levels and, if needed,
recommend treatment options that can
help avert possible progression to
glaucoma,” said Dr Weinreb, director of
the Hamilton Glaucoma Center and
distinguished professor of ophthalmology
at the University of California, San Diego,
US.
“The risk calculator helps
to identify patients with
ocular hypertension who
are at high risk of
developing glaucoma and
who may benefit from
treatment, as well as those
who are at low risk who
may not need treatment”
Robert Weinreb MD
Patients with ocular hypertension may
have multiple risk factors – such as age,
elevated intraocular pressure, thinner
central cornea, and so forth – for
progression to glaucoma, said Dr Weinreb.
A collective assessment of these risk
factors can help clinicians identify those
patients with elevated eye pressure who
are more likely to progress to glaucoma
and may benefit from early treatment. It
can also identify those that are at low risk
for progression to glaucoma who may not
need treatment. He said that similar
predictive models have been developed for
other therapeutic areas, in particular the
Framingham Study initiated in the 1950s,
which provided the basis for cardiac risk
assessment.
“We asked ourselves how this type of
therapeutic model could be applied to
glaucoma. What we wanted to achieve was
to be able to identify patients who were at
moderate to high risk for conversion from
ocular hypertension to glaucoma, as well
as those who were at low risk,” said Dr
Weinreb.
He noted that hitherto there has been
no systematic approach for physicians to
decide whether or not to treat patients
with ocular hypertension.
“Some doctors treated all patients with
high IOP and others treated very few
patients. Risk assessment not only allows
us to treat those patients who are at
highest risk but also to observe those
patients who are at lowest risk. In other
words, it allows physicians to focus their
resources and allocate their care to those
patients who are most in need,” he said.
Incorporating OHTS findings
Dr Weinreb explained that the calculator
incorporates findings from the Ocular
Hypertension Treatment Study (OHTS)
conducted in the US by the National Eye
Institute, which identified key patient risk
factors predictive of disease progression
from ocular hypertension to glaucoma.
In that multicentre study, half of 1,636
patients with high IOP were randomly
selected for treatment to lower their IOP
and half were randomly selected for
observation alone. All patients had no
optic nerve damage or visual field defects
at the time of their enrolment into the
study. After five years’ follow-up, 9.5% of
patients who were not treated progressed
to glaucoma, while 4.4% of the treated
group progressed to glaucoma in the same
time period.
Dr Weinreb said that OHTS identified
the following factors as being associated
with an increased risk of developing
glaucoma: older age, elevated IOP, thinner
central corneal thickness, increased
vertical cup/disc ratio and greater pattern
standard deviation.
Using the risk calculator, physicians can
assess these six risk factors and insert
their findings at various points on the
calculator. When taken in combination,
these factors help determine the risk of
conversion from ocular hypertension to
glaucoma within the next five years by
using a simple points system.
Validated in population study
The steps in the development and
validation of the risk calculator have been
described in detail in an article by Dr
Medeiros, Dr Weinreb and colleagues
published in Archives of Ophthalmology
(Medeiros FA, Weinreb RN, et al. Arch
Ophthalmol 2005; 123:1351-60).
Dr Medeiros said that the risk calculator
was validated in an independent
population as part of the National Eye
Institute's sponsored Diagnostic
Innovations in Glaucoma Study (DIGS) at
the Hamilton Glaucoma Center of the
University of California, San Diego, which
included 252 eyes of 126 patients with
untreated ocular hypertension.
“We evaluated the risk for glaucoma
development for each patient at the
beginning of the study and we tried to
establish if the patients at higher risk at
baseline according to the risk calculator
were actually the ones who went on to
develop glaucoma. The results showed a
good correspondence between the risk
predicted by the model and what was
observed during the follow-up of these
patients,” said Dr Medeiros.
Dr Medeiros said that the next step was
to try to determine if an estimate of
moderate to high risk as defined by the
calculator was in fact sufficient to indicate
treatment for these patients.
“Although the OHTS study provides us
with good evidence regarding the rates of
conversion to glaucoma, we still lack
reliable studies about the rate of
progression from ocular hypertension to
functional deficit and blindness. Some
retrospective studies estimate that
between 1.5% and 11% of patients with
ocular hypertension will progress to
blindness,” he said.
“Although the OHTS study
provides us with good
evidence regarding the
rates of conversion to
glaucoma, we still lack
reliable studies about the
rate of progression from
ocular hypertension to
functional deficit and
blindness”
guidelines regarding the appropriate
thresholds for treatment. Patients deemed
to be low risk (ie with an estimate of
progression to glaucoma of less than 5%)
should be monitored; those considered at
moderate risk (5%-15%) may receive
treatment depending on the final
judgement of the physician; and those at
high risk should generally receive
treatment, he said.
“Along with the risk
assessment provided by
the calculator there are
several other factors that
need to be taken into
account when deciding the
treatment strategy, such
as the patient’s overall
health status, life
expectancy and
commitment to treatment”
Dr Medeiros emphasised that the risk
calculator should be used as an adjunct to,
and not as a substitute for, clinical
experience and judgment.
“Each physician is likely to have his or
her own threshold for treatment. Along
with the risk assessment provided by the
calculator there are several other factors
that need to be taken into account when
deciding the treatment strategy, such as
the patient’s overall health status, life
expectancy and commitment to treatment,
as well as side effects from medication and
costs. They all should be weighed to
provide effective management of these
patients,” he said.
The glaucoma risk calculator was
supported in part by an independent
research grant from Pfizer, Inc, and is
distributed free of charge to interested
ophthalmologists.
[email protected]
[email protected]
Felipe A Medeiros MD
Dr Medeiros said that while the benefits
of treatment have been well established by
the OHTS study, it is also important to
determine when the benefits of treatment
outweighed the risks. He noted that a
panel of experts recently proposed
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