Article Date: 7/1/2005

Ultra Widefield Imaging with Angiography Enhances Disease Detection
Digital panoramic ophthalmoscopy complements fundus photography.

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.

Figure 1. Optomap console and monitor.
IMAGES COURTESY OF OPTOS

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.


Figure 2. A 532 nm green laser scans the sensory retina through the pigment epithelium layers of the retina.

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."


Figure 3. A 633 nm red laser scans the deeper structures of the retina from the pigment epithelium through the choroidal.

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.


Figure 4. Shows a choroidal retinal nevus superiornasal to the optic disc.

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