Ultra Widefield
Imaging with Angiography Enhances Disease Detection
Digital panoramic ophthalmoscopy complements
fundus photography.
ROCHELLE NATALONI, CONTRIBUTING EDITOR
The
ability to capture a comprehensive image of the retina is not new, but the ability
to capture a comprehensive image of the retina quickly and easily is. A digital
scanning ophthalmoscope that enables clinicians to view and digitally record up
to a 200°, internal scan of the retina, at one time and in correct orientation
in less than 1 second, compensates for the shortcomings of indirect ophthalmoscope.
The Panoramic200 scanning laser ophthalmoscope (Optos, Marlborough, MA) is becoming
a "must have" according to early adopters who have already incorporated the technology
into their practices.
The P200 scanning laser ophthalmoscope
works with Virtual Point technology and proprietary software to provide what its
manufacturer, Optos, has termed the Optomap Retinal Exam.
"One of the benefits of the P200
is that it can document an entire retina with no fuss. Depending on how complex
the patient's pathology is, this sometimes significantly decreases the amount of
drawing that we need to do in the patient's chart, as well as the amount of time
required to do it," said retina specialist Thomas Friberg, MD, chief of the retinal
service at the University of Pittsburgh Medical School. "With conventional equipment
we would have to take multiple photographs to get the same field of view that we
can with 1 scan from the P200," Dr. Friberg said. "We've always done very complete
exams all the way out to the retinal periphery, unfortunately performing those exams
and then documenting the findings took considerable time. With the P200 we get a
good, high-quality image that goes out a lot further than a normal photograph would,"
he added.
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Figure
1. Optomap console and monitor.
IMAGES
COURTESY OF OPTOS
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PANORAMIC VS. TRADITIONAL
FUNDUSCOPIC IMAGING
Joseph I.
Markoff, MD, of Philadelphia
Eye Associates, says while there is no substitute for binocular indirect viewing
of the retina, the P200 often enables visualization of pathology that occasionally
goes unnoticed with indirect ophthalmoscopy. "We're all human and we do occasionally
miss something. I've seen things on the Optomap (Figure 1) that I've missed
with the indirect," he said.
Others are finding that, as well.
For example, in a study that aimed to see if the P200 is additive or duplicative
to a dilated fundus exam, clinicians from The Eye Institute & Laser Center in
Manhattan and from SUNY, State College of Optometry, New York, found that in addition
to getting duplicative info with the Optomap, it also provides additive information
that was being missed with the other technology.1 In this study, panoramic
images were obtained as part of a comprehensive exam of 50 consecutive patients
with known or suspected disorders of the
retina and/or choroid. A traditional ophthalmoscopic exam, including fundus drawings,
was then performed, and the treating clinician reviewed the P200 images with another
clinician experienced in panoramic analysis. The result was that 13 of the fundus
drawings failed to document lesions that were found by the clinician who reviewed
the panoramic images.
Choroidal nevi, intraretinal hemorrhages,
sub-RPE hemorrhage, retinoschisis, peripheral neovascularization, peripheral retinal
horseshoe tear, and a midperipheral toxo scar were among the lesions that were missed.
The study coordinators concluded that although the P200 was originally designed
as a screening device for routine, undilated exams, the P200 appears to expose some
retinal and choroidal lesions missed during dilated fundus exams, and that it appears
to be additive, as well as duplicative, to the dilated fundus photography exam.
Jerome Sherman, OD,
FAAO, distinguished
teaching professor, SUNY, State College of Optometry, and a member of the study
team, says, "A lot of technologies that save us time give us duplicative information—essentially
providing the same information in a different or faster way. In our study we found
that in addition to confirming information found with fundus photography, the Optomap
provides additional findings. "In the best of all worlds, you want a lot of different
types of equipment because, for instance, fundus photography gives us the best possible
resolution of the posterior pole, but nothing gives us a comprehensive view like
the P200. Fundus photography is certainly better in resolution of the disc and macula,
but it is limited in terms of the amount of the fundus that it allows us to see,"
he added.
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Figure
2. A 532 nm green laser scans the sensory retina through the pigment epithelium
layers of the retina.
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LASER TECHNOLOGY
The P200 uses 2 lasers: 1 red and
1 green, which work simultaneously to image the choroid and retina. A 532 nm green
laser scans the sensory retina through the pigment epithelium layers of the retina,
and the 633 nm red laser scans the deeper structures of the retina from the pigment
epithelium through the choroid. Because the red and green lasers separate the inner
and outer retinal layers, the green laser visualizes small microaneurysms confined
to the inner retina in diabetic patients (Figure 2). The red laser visualizes the
choroidal circulation and the depth of the lesions (Figure 3). "This technology
helps us pick up lesions at a deeper level of the choroid that are often missed
with standard ophthalmoscopy," said Dr. Sherman. A strong suit of the P200 is documenting
peripheral pathology. "This is excellent for documenting peripheral issues such
as tumors, uveitis, and retinal detachment," said University of California at Los
Angeles (UCLA) retinal specialist, Steven Schwartz, MD, "and it works well in terms
of postoperative documentation, as well," he added. Dr. Friberg added that in the
case of a peripheral tumor, for instance, "this technology makes it easy to see
the progression of the tumor, and to decide if intervention needs to be rethought."
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Figure
3. A 633 nm red laser scans the deeper structures of the retina from the pigment
epithelium through the choroidal.
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Patients need not be dilated to
undergo Optomap retinal screening. While this is not always a benefit in a retinal
practice where patients are routinely dilated it can be helpful in certain clinical
entities.
"This capability has its role,"
said Dr. Markoff. "If you have a patient whose pupil is bound down because of inflammatory
disease you often cannot get a good look at the retina with an indirect ophthalmoscope.
The P200 is very effective in a situation like that. Patients who have pseudoexfoliation
syndrome, or narrow angles also benefit from this capability," he added. Performing
retinal exams on children is also much easier because of the system's ability to
forgo mydriasis, Dr. Markoff pointed out.
A recent study of the P200 used
its ability to image without dilation to its advantage by randomly imaging volunteers
at various conventions at which the equipment was exhibited.2 The volunteers
were primarily eye-care professionals. Dr. Friberg's group from UPMC Eye Center
in Pittsburg facilitated the study. "We thought it would be interesting to have
patients imaged on (a series of) exhibit hall floors to determine the prevalence
of disease in attendees who otherwise had no knowledge of having any eye problems,"
Dr. Friberg said. After informed consent and prior to imaging, subjects indicated
whether or not they had any known pre-existing eye disease or abnormalities. A total
of 512 eyes of 269 subjects were imaged. "Surprisingly, the majority of eyes had
some sort of abnormality with only 26% of eyes considered to be completely within
normal limits," he said.
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Figure
4. Shows a choroidal retinal nevus superiornasal to the optic disc.
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Drusen were found in 19.1% of eyes
and macular drusen were found in 11.3%. Suspicious optic nerves with apparent thinning
of the neural rim were found in 9.2%. Retinal hemorrhages were found in 1.6% of
eyes, and in 0.4% of eyes retinal emboli were found along a branch of the central
retinal artery. Choroidal nevi (Figure 4) were found in 6.9% of eyes and peripheral
pigmentary changes were found in 16.1%. Lattice degeneration was identified in 1.8%
of the Optomaps and peripapillary pigment atrophy was detected in 43.8% of eyes.
"We concluded that the P200 facilitates
an effective means of screening for retinal abnormalities in subjects who might
otherwise be reluctant or disinclined to present for dilated funduscopic examination,"
said Dr. Friberg.
ANGIOGRAPHIC CAPABILITIES
Fluorescein angiography with the
P200A will soon be an available component of the Optomap system. The Optos P200A
contains 3 lasers that provide red, green, and blue wavelengths. The instrument
is capable of producing the current red/green color and monochromatic Optomap image,
but with the addition of a blue laser and enhanced software, the instrument is also
capable of angiography. The angiographic mode will allow capturing a sequence of
ultra-wide field retinal images as fluorescein dye flows through the retinal vessels.
Currently in testing at Miami Veteran
Affairs Medical Center, Bascom Palmer Eye Institute; Jules Stein Eye Institute/UCLA;
and University of Pittsburgh Medical Center Eye and Ear Institute, the P200A, brought
to light rarely appreciated peripheral angiographic features and clinically meaningful
data, in studies presented at the 2005 Association for Research in Vision and Ophthalmology
meeting.
Dr. Schwartz and colleagues used
the P200A to simultaneously image the posterior pole and retinal periphery angiographically
in patients who had conditions that affect the vitreous, retinal vasculature, retinal
pigment epithelium, and conditions such as asteroid hyalosis, Coat's disease, diabetic
retinopathy, central retinal vein occlusion, branch retinal vein occlusion, retinal
detachment, traumatic macular holes, retinoschisis, retinal vasculitis, and idiopathic
polypoidal choroidal vasculopathy among other things.3
"The Optos widefield angiography
system exceeded our expectations in terms of the utility of the software, and clinical
applicability of the data obtained," Dr. Schwartz said. "We saw things that we suspected
we might find, but that we always had trouble photographing with conventional cameras.
This is rapidly becoming the angiograph of choice in patients with diffuse diabetic
macular edema and retinal vasculopathies involving the periphery, such as vein occlusions,"
said Dr. Schwartz. "In cases of garden variety, clinically significant macular edema
or diabetic macular edema, the pathology is relatively easy to treat and it is relatively
posterior. However, in cases of diffuse macular edema that are not responding to
conventional treatments, when we look at the angiogram of the periphery, we're uniformly
finding wide spread areas of peripheral nonperfusion.
"We're beginning to study applying
angiographically guided panretinal photocoagulation (PRP) peripheral lasers to these
lesions and we're hoping that we're going to be able to reverse this difficult to
treat condition," he said.
REAL-TIME IMAGING
Dr. Friberg pointed out that a
major benefit of angiography analysis with the P200A
in comparison to conventional equipment is that the entire image is captured in
the same moment with the P200A. "With the Optos system, you inject [the dye] once
and you've got the entire retina in the proper sequence," said Dr. Friberg. "To
try to get the entire retina imaged with the conventional approach is highly impractical.
It requires multiple injections, and frankly nobody does it because it's so difficult,"
he added. Another benefit, he pointed out, is that patients prefer this type of
angiogram. "All they need to do is look straight ahead. The photographer has an
easier time, and so does the patient," he added. This, he suspects, probably lends
itself to improved patient compliance.
"As retinal physicians, we're generally
savvy about using fluorescein angiography and fundus photography, but one of the
things that the P200A gives is a picture of the blood vessels and areas of the retina
that wouldn't normally be approached. In comparison, conventional fundus cameras
have about a 45°field of view," says Dr. Friberg. "When we want to see out
in the periphery in cases of diabetic retinopathy, retinal vascular diseases,
uveitis,
or vein occlusion, the P200A allows us to essentially see the entirety of the retinal
vasculature and the diseases that affect the retinal vasculature.
"Frankly, there are some things
that we're finding that weren't really well noted before because nobody could really
identify them in a practical fashion. Before we had this equipment we couldn't get
out far enough to the peripheral vasculature to make any difference on our treatment,"
he added.
For example, Dr. Friberg pointed
out, in another study presented at ARVO, he and UPMC Eye Center colleagues found
that clinically significant diabetic macular edema (CSME) appears to be associated
with measurable retinal capillary drop out located outside of the arcades in a high
percentage of patients.4
"Our findings indicate that the
subjects' vasculature in the periphery is sort of shutting down and possibly releasing
factors that have an effect on macular edema," said Dr. Friberg.
Of 17 eyes of 11 patients, the
percent of extramacular sectors showing ischemia ranged from 36%–88%, with
a mean of 71%, +/- 12%; when only 1 eye of each patient was used in the calculations,
the mean percent of sectors showing ischemia was 75%, +/-7%. After excluding 4 patients
who had undergone PRP in either eye, the neovascularization was 74%, +/-7%. No peripheral
ischemia was found in only 2 of the 17 eyes with CSME. The mean radius of each image
field across all eligible eyes was 8.9+/-1.3 disc diameters, Dr. Friberg noted.
Dr. Schwartz pointed out that acquiring
photographs as extensive as those imaged with the P200A isn't completely new. "If
you had a great photographer and a really cooperative, well-dilated patient it was
possible," Dr. Schartz said, "but with the new Optos system it's gone from being
really difficult to really easy."
TANGENTIAL PERKS
Optomap users say the technology
is an excellent patient education tool. For instance, Dr. Markoff says the Optomap
Retinal Exam has changed the way he teaches patients about the importance of retinal
health. "This technology helps me explain different retinal conditions to my patients,"
Dr. Markoff said. "For most of my patients, an Optomap Exam is a baseline against
which I can compare future exams," he added.
Beyond that, users say the panoramic
system is also an effective practice building, marketing tool.
"Patients tell their friends how
simple the exam is, and that's a real draw," said Dr. Sherman. Another benefit is
the ease with which the comprehensive images and their updates can be shared among
primary care physicians, general ophthalmologists, and retinologists. "Ultimately,
the facet of the Optomap system that I most appreciate is that after it images essentially
the entire retina, I can go back and study it extremely carefully," said Dr.
Friberg.
"When we're examining our patients, we try to be as careful as possible but we can't
go back, so being able to study the eye really carefully after we've obtained an
image enables us to detect things that we might otherwise not document."
REFERENCES
1. Nath S, Sherman J, Battaglia
M. Is OPTOS imaging additive or duplicative to a dilated fundus exam? Invest
Ophthalmol Vis Sci. 2005. 46: E-Abstract 1554.
2. King J, Friberg TR. Screening
for retinal disease in an exhibit hall environment using the non–mydriatic
Optos Panoramic 200 imaging device. Invest Ophthalmol Vis Sci. 2005. 46:
E-Abstract 1549.
3. Gonzales CR, Gupa A, Young TA,
et al. Peripheral angiographic evaluation of vitreoretinal diseases using the Optos
Panoramic200A imaging system. Invest Ophthalmol Vis Sci. 2005. 46: E-Abstract
2576.
4. Reznick
LG, Friberg TR. Detection
of capillary drop out in ultra wide angle (Optos P200A) fluorescein angiograms in
patients with clinically significant diabetic macular edema. Invest Ophthalmol
Vis Sci. 2005. 46: E-Abstract 1555.
Retinal Physician, Issue: July 2005