instrumental strategies
Diagnosis Made Easy
The Stratus OCT3 eliminates much of the
mystery in glaucoma detection.
WALTER
D. WEST, O.D., F.A.A.O.
For years I recognized, as many of you have, the
challenges in diagnosing and managing glaucoma patients. Early on, the primary
clinical indicators I used in diagnosing and managing glaucoma were patient
history, family history, ethnicity, IOP, cup-to-disk ratio and perimetry. I
recognized that IOP was a key indicator for glaucoma, but that it certainly
wasn't by itself diagnostic. In normal tension glaucoma, for instance, we
couldn't rely on tonometry alone for diagnosis, and in fact it was misleading in
many cases.
So I searched for every possible way to improve
the accuracy and reliability of the data that were available at the time. I also
evaluated new technologies as they became available to identify any other
variables for making earlier diagnoses and improved management decisions.
Looking for help
In my practice one of the first major
improvements in equipment relative to diagnosing and managing glaucoma came in
the form of the Humphrey Field Analyzer, which allowed me to automate and
thereby more consistently evaluate visual fields and monitor changes that
occurred. Although a great improvement, I recognized that perimetry wasn't an
early indicator for glaucoma as a result of the neurological makeup of the
retina. Regardless of how well any perimeter performs, before it can begin to
quantify or qualify field loss glaucoma has to have compromised or damaged 50%
of the retinal ganglion cells.
Nerve fiber layer is the key
In the late 1980s and early 1990s, much attention
was given to the relationship of the integrity of the nerve fiber layer and
glaucoma. Many of us began to incorporate a new variable in our clinical
evaluation for glaucoma: the identification and monitoring of dropout in the
nerve fiber layer, primarily in the superior and inferior papillomacular bundles
as they left the margin of the optic nerves. While those early evaluations were
crude and subjectively performed with a red-free filter on a binocular indirect
ophthalmoscope or by using a 90D pre-corneal lens and slit lamp, we began to
appreciate the diagnostic value of identifying dropout in the nerve fiber layer
in glaucoma patients and/or glaucoma suspects.
At this time, the assessments we made were purely
subjective; any appreciation of serial differential was subject to our memory,
the quality of drawings in the patients record or attempts to photo-document
with slit lamp photography. Yet even with these shortcomings -- plus the fact
that there was no way to quantify what we observed -- we recognized that changes
in the density of the nerve fiber layer within 2 to 3 disk diameters of the
optic nerve was an important variable in potentially providing an earlier
diagnosis. At the same time, it allowed us to be more proactive in our approach
to treatment.
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The OCT3 provides the
measure of nerve fiber density and the volumetric evaluation of the
optic nerve.
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Meeting the OCT3
Continuing my quest for additional diagnostic
capability, I purchased an OCT3, the most recent model of the Stratus OCT, in
the fall of 2002. I wanted to be able to assess more accurately the density of
the nerve fiber layer in evaluating my existing glaucoma patients as well as in
those patients who were glaucoma suspects. The OCT3, manufactured by Carl Zeiss
Meditec, is an optical coherence tomographer. It's similar in performance to
ultrasound but uses a light source of broadband super luminescent light instead
of sound. The result is an image with resolution that's 100 times greater than
that of ultrasound.
The OCT3 provides me with two important pieces of
information for my glaucoma and glaucoma suspect patients.
1. A volumetric representation of optic nerve
cupping. This representation of the optic nerve topography is more
meaningful to me than the typical cup-to-disk ratio because its representation
is three-dimensional. As a result, it enhances the appreciation of the
"bean pot" cupping with which some patients present. (The cupping of
the optic nerve visible at its surface isn't always the largest diameter
associated with the cupping.) Even a stereoscopic view of the optic nerve with a
binocular indirect ophthalmoscope or slit lamp doesn't reveal the full effect
that the cupping might present to the individual nerve head.
I find that the three-dimensional volumetric
representation gives me a better appreciation for the health of the rim of the
optic nerve. The serial appreciation of changes over time are more exacting as
well.
2. An objective measure of the density of the
retinal never fiber layer previously unavailable. The fact that the
assessment of the density of the nerve fiber layer using the OCT3 is objective
makes this in and of itself an advantage over the subjective format used in
gathering perimetry data. With the measure of nerve fiber density and the
volumetric evaluation of the optic nerve provided by the OCT3 as part of my
glaucoma evaluation, I can make an earlier and more confident diagnosis and
identify potentially sight-threatening clinical changes relative to glaucoma.
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CODING TIP
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Currently the CPT code for
providing service with the OCT3 is 92135. That's a unilateral code in
which you bill the procedure for the right and left eyes where
appropriate. |
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The OCT3 multitasks
As with any investment in capital equipment, the
improvement in patient care is my prime concern, but I must also know that the
use of the equipment justifies the cost of providing this service to my
patients. In my practice, using the OCT3 for glaucoma alone justifies the cost,
but this instrument isn't limited to diagnosing and managing glaucoma.
The OCT3 is also a valuable tool for evaluating
lesions and abnormalities in the macular area and throughout the posterior pole
of the retina. The imaging and improved qualification of macular irregularities
such as macular pucker, cystoid macular edema and macular degeneration provide
for even greater opportunities to employ the OCT3 to the patient's benefit.
It makes a difference
Providing patients with the most advanced
clinical diagnostics available is an integral part of my clinical practice as
well as my business plan. The OCT3 has been a valuable addition to my practice
and has enhanced the level and the consistency of my patient care.
DR. WEST IS A PARTNER IN THE PRIMARY EYECARE
GROUP OF BENTWOOD, TENN., AND A FELLOW OF THE AMERICAN ACADEMY OF OPTOMETRY. DR.
WEST IS ALSO THE CHIEF OPTOMETRIC EDITOR OF OPTOMETRIC MANAGEMENT MAGAZINE. YOU
CAN REACH HIM AT WWEST@PRIMARYEYECARE.COM.
Optometric Management, Issue: December 2003