MEDICAL DEVICE INNOVATION - Medical Device Daily

MEDICAL DEVICE INNOVATION 2010
Close accounting of the best
kind aids intraocular pressure
117
By K. JOHN MORROW Jr.
Medical Device Daily Contributing Writer
Glaucoma, a leading cause of blindness, is estimated by
the World Health Organization (Geneva, Switzerland) to
affect 70 million people worldwide. Although increased
intraocular pressure has long been recognized as its leading
cause, this pressure has proven elusive to measure
accurately. Indeed, it can vary widely over the course of the
day, and may escape detection.
There is growing consensus among students of the
phenomenon that intraocular pressure rises at night, where
it could wreak maximum havoc. A body of evidence from
circadian studies on animal models supports this belief;
pressures measured in the light phase were significantly
lower than those in the dark phase. However, the situation
in humans is complex, and both higher and lower nocturnal
pressures have been observed.
A Swiss start-up company, Sensimed (Lausanne), has
developed a novel technology for addressing this problem,
according to Dr. Matteo Leonardi, founder/chief technical
officer. The device consists of a soft disposable contact
lens with a micro electromechanical sensor embedded in it,
which allows the measurement of corneal deformation due
to intraocular pressure. The placement is non-invasive, the
lens is simply inserted over the eye as would be a standard
contact lens. A telemetry microprocessor and an antenna
are also embedded into the contact lens sensor for wireless
power and data transfer.
The other innovative component of the system is the
means of collecting and storing data. This is handled by the
contact lens sensor system, which consists of a pair of
glasses and a pocket reader. Signals from the sensor are
detected by the glasses and data are retrieved wirelessly
and stored in the pocket unit. The system allows 24-hour
continuous intraocular pressure monitoring, during which
time the patient’s movements are unrestricted.
Screening for glaucoma is currently performed by
measurements of the intraocular pressure via tonometry, a
procedure by which the amount of pressure required to
flatten a certain portion of the eye is measured, using a
tonometer. This standard procedure may be augmented
with a pachymetry to measure the cornea thickness, as this
can influence the accuracy of the pressure measurements.
Another feature of the pathogenesis of glaucoma is the role
of ocular blood flow. There is increasing evidence that ocular
blood flow is involved in glaucomatous optic neuropathy
and that unstable blood pressure and dips are linked to
optic nerve head damage. These facts further support the
utility of the Sensimed technology.
While the device was developed with its clinical applications
the foremost goal, there is a wealth of anecdotal information
as well as examples from the literature that indicate
strong interest on the part of the research community. Eye
researchers interviewed for this story waxed euphoric concerning
its possibilities for studies on both clinical and animal
models. According to ophthalmologist Dr. Douglas
Gregory, “I would also guess that researchers would drool
over the prospect of getting hold of these devices.”
Frank Liang, MD, PhD, an ophthalmologist and associate
director for in vivo studies at Advanced Vision Therapies
(Gaithersburg, Maryland), said, “Given the fact of circadian
changes in intraocular pressure, continuous monitoring by
this noninvasive device would greatly facilitate the diagnosis
and treatment of glaucoma disease by providing a comprehensive
data set throughout day and night.”
A number of published studies demonstrate the potential
applications of the Sensimed technology. These include
investigations of the effects of the drugs brinzolamide and
timolol during the diurnal period.
Clearly a convenient method of measuring intraocular
pressure during this time frame would be of great value,
allowing a range of the different conditions and combinations
to be evaluated. A related study investigated the performance
of currently available ocular hypotensive medicines
over a 24-hour time frame in patients with primary
open-angle glaucoma. Because these studies are usually
performed during the daytime for reasons of convenience
and economy, the information gathered may be inadequate
for making optimal clinical decisions.
Separate studies revealed that pressure measurements
taken outside the normal office hours change the peak
pressure assessment in 69% to 75% of cases. Finally, it has
been shown that mean peak pressure rose when measured
when measured outside normal office hours. The combination
of its promise as a research tool combined with applications
in the clinic make the Sensimed technology doubly
appealing. The contact lens could be easily modified to fit a
rabbit, a common candidate for these experimental
designs. This would open the possibility of the sort of studies
that Liang suggests, without the necessity of 3 a.m. visits
to the laboratory on the part of exhausted researchers
(or more likely their technicians).
The only drawback to the development of a research
application of the monitoring system is the availability of
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