feature
State-of-the-Art
Imaging Technology
A
review of new advances in diagnostic retinal imaging.
COMPILED BY THE RETINAL
PHYSICIAN EDITORIAL STAFF
Recent
advances in the field of retinal imaging have furthered ophthalmologists' understanding
of retinal anatomy. With today's various technologies, a comprehensive view of the
posterior segment can be realized. This capability is invaluable in diagnosing and
monitoring retinal disorders.
Here are several of the contemporary retinal diagnostic imaging
products on the market.
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The
Stratus has been used in vital clinical studies.
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►Stratus OCT (Carl Zeiss Meditec, Dublin,
Calif). The Stratus OCT provides quantitative and qualitative assessment of the
retina. With the Stratus OCT Review Software, physicians can now import, view, analyze,
and manage the Stratus OCT exam data on a personal computer.
Dana Deupree, MD, Palm Harbor, Fla, uses the OCT for determining
whether a patient needs a procedure as well as planning surgical approaches. For
example, he uses the Stratus in diabetics to find tight hyaloid membranes to gauge
if they are creating macular edema, which might be an indication for surgery. "You
can see the actual anatomy and how it is oriented to various membranes, and how
they are affecting the central macula," he notes. Dr. Deupree also uses the OCT
as a barometer to judge whether a treatment is efficacious. "It gives you an objective
measurement as to the effectiveness of the current treatment regimen; seeing the
actual histology and being able to apply an objective measurement to that as a baseline
or benchmark allows me to monitor changes," explains Dr. Deupree.
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Escalon's
product has single or dual cameras. |
►High-Resolution Imaging System (Escalon
Digital Solutions, Wayne, Pa). This system has 6 Mega-Pixel, contains full-frame
sensors, maximum sensitivity,
optimalcolor imaging, and fluorescein angiography
(FA). Image processing algorithms specifically designed for fundus imaging optimize
image quality and provide instantaneous image capture. System software includes
patient database, calibrated measurement functions, an auto montage imaging feature,
and networking and connectivity options.
Thomas
N. Fleming, MD, Belleville, Ill, uses the system primarily for age-related macular
degeneration (AMD) and diabetic retinopathy (DR) patients. He says the system is
good at picking up capillaries in and around the fovea for DR. "I like the resolution
of the pictures," says Dr. Fleming. In addition to those indications, he uses
it for branch retinal vein occlusion patients and to screen for cystoid macular
edema in post-cataract eyes.
Dennis Zukosky, ophthalmic photographer in Dr. Fleming's practice,
says, "It's a complete system; it gives the doctor what he needs and it is flexible."
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The HRA 2 is a confocal laser imaging system.
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►HRA2 (Heidelberg, Vista Calif). The Heidelberg
Retina Angiograph 2 system can change a series of optical sections into a layered,
3-D image of the retina and enables standard high-resolution, high-contract FA and indocyanine green angiography (ICGA). It also performs autofluorescense (488 nm)
imaging using the normal FA settings, but without the injection of fluorescein.
Scott Cousins, MD, Durham, NC, uses the HRA2 as a diagnostic adjunct for identifying
choroidal neovascularization (CNV) in pigment epithelial detachments; distinguishing
between CNV and retinal angiomatous proliferation (RAP); and finding what he deems
are "mature vascular complexes" in CNV. This term refers to a mature new vessel
complex that has been in the posterior segment for sometime and has a well-defined
feeder vessel and arterioles perfusing the lesion.
Dr.
Cousins finds the scanning laser system useful as it avoids the "artifacts of scattering,"
which allows a much better signal. Another important feature he utilizes is the
HRA2's dynamic, high-speed movies, which can capture up to 16 frames per second
during FAs and/or ICGAs.
Dr. Cousins says the beginning of imaging scans is
paramount and is where the most useful diagnostic information is located —
like blood-flow characteristics, for example.
"You can only get that information if you have a movie or a video,"
explains Dr. Cousins. "Whereas with a standard ICG, you are capturing 1 frame every
2 or 3 seconds, and physicians have a tendency to focus on the late frames."
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The
optomap FA images over 80% of the retina.
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►Optomap FA Digital Ultra-widefield Angiography
(Optos, Marlborough, Mass). This product produces real-time, high-resolution angiographic
images, and allows simultaneous evaluation of the peripheral and central retina.
It offers information to help monitor and diagnose eye conditions and to assist
in treatment determinations. Visualization of the periphery may help early identification
of patients at higher risk of disease progression.
Steven Schwartz, MD, Los Angeles, has had the benefit of experience
with the optomap FA as his practice has been working with the prototype. "We have
found it useful for all retinal vascular disease," says Dr. Schwartz. He also credits
its ease of use.
Within his practice, he and fellow surgeons have preferred using
it to conventional angiography. Dr. Schwartz also credits the widefield view, and
says it allows physicians to get a more comprehensive view of the retina. He points
specifically to its ability to detect retinal non-anterior perfusion early.
While
he points out this is a new technology, he is optimistic about the optomap FA in
the long view. "It has the potential to have a big impact [in diagnosing retinal
disease,"] says Dr. Schwartz.
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The OCT/SLO has a single
super-luminescent diode.
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►OCT/SLO (OTI, Toronto, Ontario). OCT and SLO images of the fundus are produced simultaneously through the same optics. The
OCT and SLO images correspond pixel to pixel. OCT images can be acquired either
as B-Scan of the retina and/or as a parallel sectional stack of C-Scan images at
variable depths.
Richard Rosen, MD, New York, utilizes the OCT/SLO primarily for
AMD and DR screenings. He finds it to be effective with its ability to combine B-
and C-scans, and it allows him to obtain a comprehensive view of the posterior segment
from front to back."You can correlate the surface of the eye, with what is going
on inside," says Dr. Rosen.
Dr. Rosen also likes how the OCT/SLO images are scanned compared
to other diagnostic products. "When you scan parallel to the surface, you have better
continuity." This allows him to locate more "subtle pathologies."
►Retinal Thickness Analysis (RTA 5) (Talia/Marco,
Jacksonville, Fla). Outputs include thickness and topography analysis, interactive
3-D imaging, retinal nerve fiber layer measurement, optical cross sections, digital fundus imaging, and an overlay of a 2-D thickness map onto a patient's digital fundus
image. The RTA 5 offers its "Vision Wellness" report for baseline exams. A new 'Dynamic
3-D Anatomy Imager' program allows continuous visualization and quantitative analysis
through each cross-sectional slit image, across any scanned field.
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The
RTA 5 is made by Talia and sold by Marco. |
Sara Krupsky, MD, Rehovot, Israel, uses the RTA 5 to detect and
monitor a variety of ailments. "The RTA 5's high-quality fundus photography with
thickness mapping makes it an excellent tool to detect DR and follow these patients
after treatment." She also uses it identify conversion of dry to wet AMD and to
monitor CNV resolution following treatment. As Dr. Krupsky has the RTA in her practice,
she uses it as an indicator for pathological changes (subretinal fluid, pigment
epithelial detachment, macular edema) thus avoiding repeated and invasive FA testing.
►TRC-NW6S
(Topcon, Paramus, NJ). This non-mydriatic fundus camera's 9 internal fixation
LEDs help document a wide-aspect view of retina. Angle data and OS/OD information
transfers automatically to IMAGEnet software. IMAGEnet provides a myriad of software
features to make the images useful in managing patient compliance and monitoring
disease progression.
Douglas Kaplan, MD, Chicago, uses the TRC-NW6S to monitor progression
of dry AMD, document and treat DR, and establish baseline imaging in retinal/choroidal
lesions. Dr. Kaplan also shows his AMD and DR patients their images from the TRC-NW6S.
He believes it is a beneficial tool in helping these patients understand their diseases
and participate in their own care.
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Topcon's TRC-NW6S offers 45Þand 30Þ
fields.
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"When they can see what is happening to their eyes, it really
boosts their knowledge and compliance," he says.
CONTINUOUS INNOVATION
Today's systems provide a more comprehensive
view of the posterior segment. As the technology continuously improves, it will
further aid physicians with diagnostic challenges in helping to identify hidden
pathologies.
Retinal Physician, Issue: July 2006