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Retinal analyzers: well worthwhile in glaucoma practices
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In glaucoma screening, there is not yet one all-encompassing test that provides a conclusive “yes or no” answer. A definitive diagnosis is often culled through several different methods, including visual field testing, tonometry and analysis of the optic nerve and nerve fiber loss.
“I keep an open mind about glaucoma, because I don’t believe we know nearly as much about it as we think we do,” said Joe Wesley DeLoach, OD, in private practice at Plano Eye Associates in Plano, Texas. “I believe glaucoma is much more prevalent than we think it is. If we have better tools to find those early glaucoma patients, as opposed to finding the 80-year-old grandmother with half of her visual field gone, we’re doing a much better job of taking care of our patients.”
Among these tools are optic nerve analyzers and nerve fiber analyzers, both of which have begun to play an increased role in the armamentarium of primary care optometrists. Although this instrumentation represents a sizable expenditure for any practice, many optometrists maintain that it is money well spent.
“Initially, I thought that my practice couldn’t afford such an instrument,” said John A. McCall Jr., OD, private practitioner in Crockett, Texas. “But when I saw what it did, and I looked at my practice, I realized I couldn’t afford not to have it.”
For many practitioners with a high volume of glaucoma patients or suspects, a retinal analyzer has proved to be a worthwhile investment.
“I think this is almost invaluable if you’re managing early glaucoma,” said Dr. DeLoach. “We don’t usually see optometric practices investing in high-tech equipment, but I think this is the tool for optometry. It does so many things that will allow us to make better diagnostic decisions, and that’s what optometry is all about.”
The Heidelberg Retina Tomograph
One retinal and optic nerve topographer currently available to practitioners is the Heidelberg Retina Tomograph (HRT) from Heidelberg Engineering (Carlsbad, Calif.). The HRT is a confocal scanning laser microscope that enables the quantitative assessment of the optic nerve and retinal topography and follow-up of topographic changes.
The HRT images and measures the surface topography of the optic nerve and retina. With this test, the practitioner is interested in topographic measurements of the optic nerve and surrounding retina. Measurements are available for the area and volume of the optic nerve, cup, rim tissue, slope of the cup walls and height of the retina adjacent to the optic nerve.
Christopher Quinn, OD, in practice in Iselin, N.J., has worked with the HRT for 7 years and currently owns two units. Dr. Quinn said the HRT is especially effective in following a patient’s progress over time.
“We recognized early on that the more objective data you could collect on patients with glaucoma, the better that would serve you in the long run, as far as being able to use that data for comparison in the future. That’s what the Heidelberg really is best at.”
Murray Fingeret, OD, of St. Albans VA Hospital, St. Albans, N.Y., first purchased an HRT 4 years ago and continues to use this instrumentation in his practice today. “I have found it to be a very effective instrument,” Dr. Fingeret said. “The main idea behind this instrument is the ability to pick up and detect changes over time. I wanted a tool that, in particular, would allow me to detect change as early as possible.”
Robert Wooldridge, OD, clinical director of the Eye Foundation in Salt Lake City, did significant research before choosing the HRT.
“I would recommend that practitioners research the literature out there for good clinical studies on the instrumentation,” Dr. Wooldridge said. “I also talked to everyone I knew who owned one of the instruments.”
Additionally, Dr. Wooldridge sampled two different units at his practice for a brief “trial period.”
“I strongly advise doctors to put one of these in their office for a day or so and schedule as many glaucoma patients and glaucoma suspects as they can beforehand,” Dr. Wooldridge said. “I did that with two instruments, one of which I, frankly, did not get satisfactory information from.”
Dr. Wooldridge said practitioners should purchase a retinal analyzer with realistic expectations about the instruments’ capabilities.
“We should be careful when we look at marketing information from these companies claiming incredibly high degrees of sensitivity and specificity,” Dr. Wooldridge said. “To Heidelberg’s credit, that company has not done that. We need to look at multiple studies and determine if these numbers are repeatable.”
Dr. Quinn said he would recommend the HRT to any optometrist who wishes to build on his or her glaucoma practice.
“I would say that any optometric practice that is serious about developing and managing glaucoma patients should consider having this as a tool,” Dr. Quinn said. “It may not show an immediate benefit to the practice, but, as time goes by, it will. The most utility from the instrument will be not a year later, or 2 years later, but 5 or 10 years later, when you’re really faced with the dilemma of deciding whether or not the patient is getting worse.”
The LDT GDx
The GDx Nerve Fiber Analysis System by Laser Diagnostic Technologies Inc. (LDT, San Diego, Calif.) is a confocal scanning ophthalmoscope with an integrated polarimeter. The GDx measures the thickness of the retinal nerve fiber layer and then analyzes the results, comparing them to a database of normative values. The company also provides a portable, per-use lease version of the GDx, the GDx Access.
Andrew Goodfriend, MD, assistant clinical professor of ophthalmology at the University of Rochester, opted to purchase a GDx for his nine-doctor practice. Dr. Goodfriend said his practice has owned the unit for about a year.
“I have found it to be quite effective,” Dr. Goodfriend said. “It has actually provided me with information that has led me to begin treatment, and so I have found it to be very helpful.”
Dr. Goodfriend said a key distinction of the GDx is its measurement of the nerve fiber layer, as opposed to nerve contour. “It actually looks at nerve fiber layer, whereas some of the other instruments look at the contour of the optic nerve,” he said. “That’s also good information — don’t get me wrong. But we’ve never really taken a good look at the nerve fiber layer itself.”
Dr. Goodfriend said he uses the GDx primarily on patients with early to moderate glaucoma, as well as glaucoma suspects. “We’re establishing a baseline with this unit,” Dr. Goodfriend said. “And just like with visual field, you’re allowing for changes over time.”
Dr. Goodfriend said he has now owned the unit long enough to notice small changes in his glaucoma patients.
“As I repeat the test over time, I’m finding changes,” Dr. Goodfriend said. “It is really helping me find some subtle changes on the order of about 10 to 12 µm of nerve tissue and some very specific changes that have indicated that certain patients have advanced in their glaucoma. And that was a lot sooner than I would have noted before.”
Richard C. Edlow, OD, a practitioner based in Baltimore, owns two GDx units. He said the instrumentation is especially valuable in preventing erroneous or premature treatment. “It helps us keep patients off of needless treatment,” he said. “For the most part, once you institute treatment for glaucoma, patients are on it for life.”
Dr. Edlow said he has seen patients with pressures of 25 or 26 mm Hg, but a normal visual field. He said that although in the past this may have precipitated treatment, his practice now makes a final determination for such a patient after running the GDx.
“Now, if we have a patient with a pressure of 25 mm Hg, a normal field and a normal nerve fiber, we will just follow him or her,” Dr. Edlow said. “If we can keep 2% of our patients from being needlessly treated, this instrument is great.”
The LDT TopSS
The Topographic Scanning System (TopSS) is a scanning laser tomograph that was introduced by Laser Diagnostic Technologies in 1993. Like the HRT, the TopSS provides the topography and volumetric analysis of the optic nerve.
“It enables the clinician or practitioner to diagnose glaucoma before advanced damage to the optic nerve occurs,” Dr. McCall said. “Without this type of equipment, the only way you can identify glaucoma with 100% certainty is increased visual field loss. And we have always known that you have to lose more than 50% of the optic nerve before you develop visual field loss.”
Dr. McCall purchased a TopSS in 1996 and said he has been pleased with the performance of the unit. “Because of the information I get from it, I have not regretted for one moment purchasing the instrument,” he said. “You can compare the data with future information, to determine if the nerve is eroding.”
Craig Andrews, OD, a private practitioner in Illinois, said the TopSS unit has been very useful in several applications.
“It gives us a 3-D image of the optic nerve, and it is very useful to compare from one visit to the next,” he said. “Also, it is an objective way to keep track of changes due to glaucoma. Visual field tests are subjective.”
Dr. Andrews said he has also used the TopSS to look at macular problems. “We can measure the depth of a macular hole,” he said. “It doesn’t help with macular degeneration, but it does help with macular holes.”
Any cup size of 0.5 or larger or any difference in cupping of 0.2 between the two eyes would necessitate a scan with the TopSS, Dr. Andrews said.
“I feel that there are two groups of patients with glaucoma,” he said. “There are those with normal-looking cups but with fields showing glaucomatous damage. And then there are those whose fields look really good, but whose cups look terrible and are changing. Those are really the patients I am watching most closely with the TopSS unit.”
Dr. Andrews added that the TopSS unit facilitates patient awareness of glaucoma. “The patients love it, because I can show them on a wall chart what a normal optic nerve looks like and what theirs looks like,” he said. “And they can see where they’re different, and they have no doubt as to why you’re working with them. It’s great for patient education.”
Talia’s Retinal Thickness Analyzer
The Retina Thickness Analyzer (RTA) is an instrument introduced by Talia Technology, Ltd. (Tel Aviv, Israel). Retinal thickness analysis is a quantitative and qualitative way to assess abnormalities in the posterior pole, especially in the macula.
The RTA process is similar to slit-lamp biomicroscopy in that the separation between the reflections from the vitreoretinal interface and the chorioretinal interface is a measure of the retinal thickness.
“Historically, many of the instruments have measured nerve fiber layer thickness at the superior and inferior poles of the optic nerve,” said Dr. DeLoach. “That has always been thought to be the site of early damage in glaucoma. With my 15 years of working with glaucoma patients, I strongly believe that in many cases, early damage from glaucoma occurs in the papillomacular bundle, as opposed to the arcuate bundle of the retina. This is the only instrument that measures nerve fiber layer thickness throughout the entire posterior pole as well as the superior and inferior arcuate bundles.”
Dr. DeLoach, who has worked with an HRT for about 10 years, decided that his practice needed additional tools for its glaucoma patient base. “The RTA was in line with a lot of what I had been doing over the past 10 to 15 years with the posterior pole,” Dr. DeLoach said. “Also, the RTA is a good tool to use outside of glaucoma.”
Dr. DeLoach said the RTA measures not only optic nerve topography, but nerve fiber layer thickness throughout the posterior pole. “We can use this as a diagnostic tool in any retinal conditions that affect the posterior pole, whether it be hypertensive retinopathy, diabetic retinopathy or macular holes,” Dr. DeLoach said. “So I found that the diversity of the instrument’s diagnostic capability was far above anything else that was available.”
Dr. DeLoach said he believes that the RTA is definitely a wise investment for practices dealing with glaucoma patients. “The additional information the RTA gives us is invaluable to our patients,” Dr. DeLoach said. “It’s an expensive instrument, but because of the diversity with which you can use it, it more than pays for itself.”
Humphrey’s OCT
Optical Coherence Tomography (OCT) from Zeiss Humphrey (Dublin, Calif.) features a non-contact, non-invasive method of obtaining cross-sectional retinal images.
“We found that it could give us everything we really wanted in one unit — it would analyze nerve fiber thickness for glaucoma and macular thickness for diabetic macular edema,” said Terry Schultz, OD, clinic director of Eye Specialists in Ohio.
Dr. Schultz and his colleagues learned about the instrument at the American Academy of Cataract and Refractive Surgery meeting in San Diego. “That’s a good place to compare different instruments, because the manufacturers are all there,” Dr. Schultz said. “So we compared the OCT to others, and we found that the OCT will map out a specific cup-to-disc ratio and measure macular thickness for retinal problems. The retinal thickness measurement was really valuable to us.”
Dr. Schultz said he uses the OCT every day and has found it to be extremely useful. “We’re even considering doing baseline scans on everyone who is diabetic, because they could have minimal amounts of diabetic macular edema, and it doesn’t really affect their vision that much,” he said. “And we can use that information later on, because, typically, someone diagnosed with diabetes will usually have changes in his or her retina about 10 years after the diagnosis.”
Some insurance companies consider this technology experimental, said Dr. Schultz. His practice would definitely scan any glaucoma suspect as well as those with diabetic eye problems that are visible to the naked eye. “These patients and the doctors want the test, regardless of insurance issues,” he said.
“If we look inside someone’s eye and see that he or she has diabetic macular edema or other conditions of the retina, such as a choroidal neovascular membrane, we’ll scan the patient for that, too,” he continued. “For my practice, this instrument was worth the money.”
Insurance companies: help or not?
Many practitioners maintain that they have had few problems gaining insurance reimbursement for patients who are scanned with a retinal analyzer. Under the American Medical Association’s Current Procedural Terminology (CPT) codes, the instruments qualify as “confocal scanning lasers.”
“Generally, once the AMA has developed a CPT code for a piece of diagnostic equipment, as they have done for this,” Dr. McCall said, “you have an arguable reason for the insurance company to pay, under the right diagnosis.”
Nevertheless, this is not always the case, according to some practitioners. While Medicare and Medicaid currently cover the test, some smaller insurance companies have failed to acknowledge its clinical utility.
“Unfortunately, that’s still the case,” said Lee Peplinski, OD, in practice in Louisville, Ky. “We were probably among the earlier people on the curve for this, and we fought a lot of those battles. Certainly Medicare and Medicaid acknowledge this, and most of our private pay insurers do, too.”
Dr. Peplinski said that at least one company continues to deny coverage. “They deny it on the basis that it is still investigational, despite industry’s attempts, my attempts and the other practitioners’ attempts to show otherwise,” Dr. Peplinski said. “We have even enlisted the patients now to write and call the medical director for this carrier.”
Dr. Peplinski began giving every patient with this particular insurance a tear sheet encouraging him or her to write or call the company. “The sheet provides the name, address and phone number of the insurance company that is denying the benefit,” he said. “It urges patients to ask the company why they refuse to authorize payment.”
A piece of the puzzle
Although retinal analysis is playing a more pivotal role in diagnosing glaucoma, practitioners agree that it needs to be done in conjunction with other screening tools.
“I don’t think we can throw our visual field instruments away,” Dr. DeLoach said. “I think from a standard of care viewpoint, it is still important to obtain visual field information.”
Dr. Quinn agreed that retinal analysis cannot stand alone. “There is no doubt that none of these instruments have reached the point where they’ve replaced any of the other tools we use to manage glaucoma,” he said. “They provide more information in addition to what we currently have about the management and diagnosis of glaucoma.”
Dr. Goodfriend maintained that, in glaucoma testing, there still is no all-encompassing method. “It’s a good tool, but, just like visual field testing, there is no ideal tool,” he said. “The way I look at it is that it’s a piece of the whole puzzle in the diagnosis and treatment of glaucoma.”
For Your Information:
- Joe Wesley DeLoach, OD, can be reached at 5900 Colt Rd., Plano, TX 75023-5248; (972) 985-1412; fax: (972) 964-5758. Dr. DeLoach has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- John A. McCall Jr., OD, is a member of the Primary Care Optometry News Editorial Board. He can be reached at 711 East Goliad Ave., Crockett, TX 75835; (936) 544-3763; fax: (936) 544-7894. Dr. McCall has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Christopher Quinn, OD, can be reached at 485 Rte. 1, Iselin, NJ 08830; (908) 750-0400; fax: (732) 750-1507. Dr. Quinn has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Murray Fingeret, OD, is a member of the Primary Care Optometry News Editorial Board and practices at St. Albans VA Hospital in St. Albans, N.Y. He can be reached at Linden Blvd. and 179th St., St. Albans, NY 11425; (718) 526-1000 ext. 2435; fax: (516) 569-3566. Dr. Fingeret has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned. He has lectured on behalf of Heidelberg.
- Robert Wooldridge, OD, can be reached at 201 E. 5900 S., Ste. 201, Salt Lake City, UT 84107-5431; (801) 268-6408; fax: (801) 262-9216. Dr. Wooldridge has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned. He is occasionally sponsored as a speaker by Heidelberg.
- Andrew Goodfriend, MD, can be reached at 1580 Elmwood Ave., Rochester, NY 14620; (716) 244-2580; fax: (716) 244-3741. Dr. Goodfriend has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Richard C. Edlow, OD, is chief operating officer for Katzen Eye Group in Baltimore. He can be reached at 901 Dulaney Valley Road, Towson, MD 21204; (410) 821-9490; fax: (410) 821-0104. Dr. Edlow has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Craig Andrews, OD, can be reached at 400 N. Broadway, Salem, IL 62881-1514; (618) 548-3506; fax: (618) 548-2555. Dr. Andrews has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Terry Schultz, OD, is clinic director of Eye Specialists. He can be reached at 784 E. Main St., Lancaster, OH 43130-1010; (740) 477-7200; fax: (740) 654-7109. Dr. Schultz has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
- Lee Peplinski, OD, practices at the Bennett & Bloom Eye Centers in Louisville, Ky. He can be reached at 4500 Churchman Ave., Louisville, KY 40215-1110; (502) 364-0033; fax: (502) 361-4488. Dr. Peplinski has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.