Tools for AMD detection, management going high-tech

As the number of people at risk for developing age-related macular degeneration (AMD) advances, so do the high-tech devices able to predict, diagnose and monitor the potentially blinding disease.

Five such technologies are the Foresee PHP, Heidelberg Engineering’s HRT, MacuScope, optical coherence tomography (OCT) and QuantifEye, testing systems that range from reportedly determining a patient’s risk factor to detecting subtle changes in the macula, sometimes before AMD converts from the atrophic to the more critical exudative phase.

“By using imaging technologies such as OCT and HRT, we are provided with additional diagnostic information that may help to elucidate that conversion,” Boston-based practitioner Anthony Cavallerano, OD, FAAO, a Primary Care Optometry News Editorial Board member, said in an interview.

For many optometrists, the reasons for having the devices are clear.

“For every glaucoma patient in our office, there are three macular degeneration patients,” Richard Noyes, OD, who practices in Marion, Iowa, told PCON. “Macular degeneration is not a disease you can ‘back the truck up’ for. That means we need to be interacting as early as we can in the course of the disease, particularly in those patients who are going to have a negative outcome.”

Foresee PHP analyzes central visual field

The first generation device known as the Preview PHP (Carl Zeiss Meditec, Dublin, Calif.) has been updated and introduced as the second generation PHP — Foresee PHP (Notal Vision/MSS, Bloomington, Minn.)

The PHP, or Preferential Hyperacuity Perimeter, is designed for early detection of the conversion to CNV. The device is approved by the Food and Drug Administration to analyze the 14 degrees of a patient’s central visual field.

The PHP exam helps practitioners identify elevations in a patient’s retinal pigment epithelium (RPE) and “the bowing of the photoreceptor layer,” both consistent with conversion to choroidal neovascularization (CNV), according to company literature.

The technician-assisted test is used to monitor dry AMD. Patient test results are compared to a normative database so the disease can be tracked over the long term. It has been clinically shown to detect conversion to wet AMD at an early stage.

Thomas R. Cheezum, OD, of Chesapeake, Va., uses the PHP as a monitoring device.

“The PHP presents targets to patients at different levels of acuity that will help detect if they are seeing bends in the lines presented,” Dr. Cheezum told PCON. “The computer will note that and coordinate all the information and tell me if there is something that we need to be concerned about or not concerned about.”

During the test, a patient rests his or her head on a chin rest and looks directly at the screen. Line targets come in and out of focus in various positions, and the patient, using a stylus, points to any bends he or she sees in the lines on the screen.

Historically, practitioners, using the typical diagnostic metrics including the Amsler grid, slit lamp microscope and fundus lens, would be able to detect a CNV lesion at about 3,300 µm and, often, after the lesion has become subfoveal.

“The PHP will pick up these lesions at 1,100 µm extrafoveally,” Dr. Noyes said. “Now we can catch them when they are smaller and outside the fovea, and that gives us a better way to treat them, either with an intravitreal injection or thermal laser, whichever is in the patient’s best interest.”

Dr. Cheezum said vision can be saved by using the PHP because the device accurately picks up early conversion, allowing him to refer patients to a retinal specialist for an OCT test.

“Two patients we had who were converting noticed no difference in their vision,” Dr. Cheezum said. “When we checked them on the PHP we noticed that they were beginning to convert. We referred them to the retinal folks and were able to stabilize their vision and get them treated right away at 20/40. It’s a very useful instrument.

“The results the retinal specialists are sending back to me with the OCT are fairly consistent with what we are finding with the PHP,” he added.

All visual field technology, including this one, have some degree of learning curve for the patient being tested, Dr. Noyes said. “If the result does not make sense to me based on the clinical picture, I may repeat in 2 weeks and look for repeatability of the anomolous result or progression,” he said. “If the instrument reports ‘reliable results’ on its auto check, if I believe the patient results to be credible and the patient has intermediate to advanced dry AMD, I’ll typically repeat at 3 months. At this level of testing, we hit a specificity and, more importantly, a sensitivity of about 80%. That is a big deal.”

For patients with less advanced disease, Dr. Noyes said he may order the test at 4- or 6-month intervals. However, he always considers that choroidal neovascular membrane growth is in the range of 20 microns per day, so longer periods between evaluations increases the risk of undetected growth. “Larger lesions have statistically poorer outcomes because of the danger of subfoveal extension,” he added.

“Therefore, it comes down to the cost/benefit ratio for the patient,” Dr. Noyes said. “That is where optometrists shine. We are a group that is careful as clinicians and yet we have an eye toward cost.”

HRT provides edema, thickness measurements

The Heidelberg Retina Tomograph (HRT), from Heidelberg Engineering (Vista, Calif.), uses a confocal scanning laser ophthalmoscope and TruTrack image alignment technology to detect subtle progression and create 3-D retinal thickness maps.

Stuart P. Richer

“Retinal thickness measurements enable the identification and tracking of structural changes due to retinal pathologies,” according to company literature.

“The newest version of the software produces 2-D (15° x 15°) retinal edema images of the macula and composite 3-D images that display both an edema map and retinal thickness,” Stuart P. Richer, OD, PhD, FAAO, who uses the HRT in his Chicago practice, told PCON. “With respect to exudative AMD suspects and actual cases under medical treatment, the edema and thickness information is useful, as an adjunct to fluorescein angiography, in identifying retinal thickening secondary to subretinal neovascularization, and less often intraretinal neovascularization.”

MacuScope determines risk

The MacuScope (MacuChek, West Bloomfield, Mich.), is showing promise in helping practitioners determine a patient’s risk for developing AMD.

Using heterochromatic flicker photometry (HFP), the MacuScope measures the density, or absorbance, of a patient’s macular protective pigment, which is composed of lutein, meso-zeaxanthin and zeaxanthin, carotenoids that researchers believe protect the macula. They do so by absorbing harmful high energy blue light that causes photochemical damage and containing extremely high anti-oxidative properties. Of particular importance is the fact they they are only found in the center of the macula and reside anterior to the RPE and photoreceptors below.

The patient places his or her head against the viewfinder and observes a small, flickering blue/green light. He or she is then asked to tell the tester when the flicker is slowing down and, finally, when the flickering stops altogether.

“A person with a dense macular pigment will require more blue light to achieve the no-flicker or minimum flicker condition compared with a person having little macular protective pigment,” according to company literature written in 2004 by John Landrum, PhD, and Richard Bone, PhD, the inventors of the device and the researchers who dicovered lutein and meso-zeaxanthin.

The instrument determines whether the patient’s pigment is low, average or high and then gives the tester gives a number between 0 and 1 that places the patient into a risk category based on a normative database. An average person has a 0.42 measurement, which decreases over time. Damage caused from low macular pigment is permanent and cumulative over a lifetime.

David W. Nelson

“The research shows that macular pigment optical density (MPOD) decreases with age, starting around age 30, and that those who develop macular degeneration statistically have much lower MPOD than others,” David W. Nelson, OD, MBA, who practices in Madison, Wis., told PCON in an interview. “We actually can have an instrument in the primary eye care office that allows us to detect changes that we now know may result in macular degeneration in several decades.”

Dr. Nelson screens all of his patients 30 and older with the MacuScope.

“Those younger individuals who have 0.3 or less are targeted as patients who may develop macular degeneration over the next three or four decades, if they are in their 30s,” Dr. Nelson said. “We are correlating the people who have a low reading, a family history and other risk factors, asking them to come back every 6 months after taking a supplement containing lutein, meso-zeaxanthin and zeaxanthin.”

The supplement, Dr. Nelson said, helps build the macular pigment back up over a 6-month period. After that, he asks the patients to come in and be tested on the MacuScope yearly.

Elaine Happ, OD, uses the Macu-Scope in her practice in Monticello, Minn., as well, and suggests supplements to her at-risk patients.

“The goal is to identify the people at risk, get them on the supplements and prevent them from developing macular degeneration in the first place,” Dr. Happ said in an interview.

OCT indicates retinal thickness

OCT uses near infrared frequency light to obtain an image and measures retinal optical reflectivity to generate a map indicating retinal thickness. OCT technology is available through Stratus OCT and Cirrus HD-OCT/Carl Zeiss Meditec, Spectralis OCT/Heidelberg Engineering, Bioptigen (Research Triangle Park, N.C.) and RTVue-100/Optovue (Fremont, Calif.).

Dr. Cavallerano uses the Stratus OCT (Carl Zeiss Meditec, Dublin, Calif.), to achieve a high-resolution, cross-section and color-coded structural view of the macula and layers of the retina, including the vitreomacular interface.

“OCT is an excellent technology because it provides us a virtual biopsy of the structures of the macula,” Dr. Cavallerano told PCON. “Based on ultrasound principles but relying instead on a light-based (820 nm) source, a beam of light is directed into ocular tissue layers, and reflections coming from different layers of the tissue are processed, reconstructed and color-coded, depending on the amount of reflectance from those structures. Areas of the macula that are highly reflective will show up as red on the external band with OCT. Black, on the other hand, indicates very low reflectance, and yellow-green anything that’s in between.”

Dr. Cavallerano uses the device on his AMD patients to look for “qualitative and quantitative changes in the deeper layers of the neurosensory retina in the macula along with the outer retina complex: the retinal pigment epithelium, Bruch’s membrane and the choriocapillaris.”

OCT also allows him to look carefully for changes over time and for the development of CNV over time.

QuantifEye determines risk factor

Like the MacuScope, the QuantifEye (ZeaVision Inc., St. Louis) uses HFP to determine a patient’s MPOD.

During the exam, a patient places an eye on the device and watches until he or she sees a light, blue flickering light. When that happens, the patient presses a response button, and the responses appear on a screen to help validate the accuracy of the test. A score between 0 and 1 is generated.

Dr. Richer uses the device when examining at-risk patients and explained how it works.

“The testing process results in central and peripheral sensitivity curves presented in an elegant computer software display, as the patient presses a button 15 to 25 times per eye to generate the flicker response to varying ratios of the blue/green mixture of light,” he said. “HFP is based on the principal that macular pigment is highest in the fovea, where the blue wavelength is retarded compared to the green wavelength.”

ZeaVision also promotes a professional-only nutritional supplement called EyePromise Restore with the QuantifEye. The supplement contains high doses of dietary zeaxanthin, lutein and omega-3, along with other antioxidants.

“If a patient is at high risk with low MPOD, he or she can be advised to consume spinach and yellow peppers, for lutein and zeaxanthin, respectfully, and omega-3 containing fatty fish (i.e., sardines, salmon, tuna and herring), which appear to have a synergistic effect,” Dr. Richer said. “Nutritional supplements are also quite effective in raising macular pigment optical density.”

Doctors who give patients the supplements usually ask them to come in for a follow-up visit in 6 months, he said.

One can also obtain “low-tech” complementary visual function data by performing what Dr. Richer calls a “2-minute CSF test.” In this simple contrast sensitivity test, the doctor varies the contrast of monocularly viewed 20/70 (low spatial frequency), 20/50 (medium spatial frequency) and 20/30 (high spatial frequency) letters on the flat screen visual acuity projector chart. See the accompanying table that indicates an improvement in CSF after 6 months use of Ocuvite with lutein (Bausch & Lomb, Rochester, N.Y.)

For more information:

• Anthony Cavallerano, OD, FAAO, is a Primary Care Optometry News Editorial Board member who practices at VA Boston Health Care System, Jamaica Plain Campus. He can be reached at 150 S. Huntington Ave., Boston, MA 02130; (857) 364-2281; fax: (857) 364-6538; e-mail: tonycav@earthlink.net. Dr. Cavallerano has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Richard Noyes, OD, can be reached at Iowa Eye Care, 1065 E. Post Rd., Marion, IA 52302-5214; (319) 377-2222; (319) 377-2967; e-mail: rnoyes@iowaeyecare.com. Dr. Noyes has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Thomas R. Cheezum, OD, can be reached at 801 Volvo Pkwy., Ste. 133, Chesapeake, VA. 23320; (757) 549-2225; fax: (757) 549-0380; e-mail: tcheezum@cox.net. Dr. Cheezum has no direct financial interest in the products mentioned in this article, nor is he a paid consultant for any companies mentioned.
• Stuart P. Richer, OD, PhD, FAAO, is chief of optometry at Department of Veterans Affairs North Chicago and associate professor of Family & Preventive Medicine at Rosiland Franklin University of Medicine and Science/Chicago Medical School. He can be reached at 3001 Green Bay Rd., North Chicago, IL 60064-3095; (224) 610-5440; fax: (224) 610-2924; e-mail: stuart.richer1@med.va.gov. Dr. Richer is also an associate professor of optometry at University of Missouri-St. Louis and Illinois College of Optometry. He has no direct financial interest in the products mentioned in this article, but is a paid consultant for Bausch & Lomb.
• David W. Nelson, OD, MBA, can be reached at 7428 Mineral Point Rd., Madison, WI 53717-1710; (608) 833-4242; fax: (608) 833-4248; e-mail: AmOptBdDWN@aol.com. Dr. Nelson has no direct financial interest in the products mentioned in this article, but he is a paid consultant for MacuChek.
• Elaine Happ, OD, is the owner of Uptown Eye Care and member of Vision Source, Minnesota. She can be reached at 560 Cedar Street, Monticello, MN 55362; (763) 271-2020; fax (763) 271-2030; e-mail: ehapp@uptowneyecare.com.

• MSS can be reached at 5775 W. Old Shakopee Rd., Ste. 80, Bloomington, MN 55437; (952) 881-2500; (800) 728-9615; fax: (952) 881-1700; e-mail: info@ms-services.com; www.ms-services.com.
• Heidelberg Engineering can be reached at 1499 Poinsettia Ave., Ste. 160, Vista, CA 92081; (800) 931-2230; fax: (760) 598-3060; e-mail: ContactUSA@HeidelbergEngineering.com; www.heidelbergengineering.com.
• MacuChek can be reached at 5640 W. Maple Rd., Ste. 112, West Bloomfield, MI 48322; (800) 404-4170; fax: (248) 538-7720; e-mail: info@macuscope.com; www.macuscope.com.
• Carl Zeiss Meditec can be reached at 5160 Hacienda Dr., Dublin, CA 94568; (877) 486-7473; fax: (925) 557-4778; www.meditec.zeiss.com.
• ZeaVision can be reached at 424 South Woods Mill Rd., Ste. 330, St. Louis, MO 63017; (866) 833-2800; e-mail: info@zeavision.com; www.zeavision.com.

References:

• Nolan JM, Stack J, O’Donovan O, et al. Risk factors for age-related maculopathy are associated with a relative lack of macular pigment.Experimental Eye Research (2006), doi: 10.1016/j.exer.2006.08.016.
• Olsen TW, Feng X, Kasper TJ., et al. Fluorescein angiographic lesion type frequency in neovascular age-related macular degeneration. Ophthalmology. 2004;111(2):250-255.
• Prevent Blindness America and National Eye Institute. Vision Problems in the U.S.: Prevalence of adult vision impairment and age-related eye disease in America. 2002. Available at http://catalog.nei.nih.gov/productcart/pc/viewPrd.asp?idcategory=2&idproduct=47#. Accessed July 16, 2007.
• Richer SP, Stiles W, Statkute L, et al. A placebo-controlled, double-blind, randomized trial of lutein and antioxidant supplementation for the treatment of age-related macular degeneration: The Lutein Antioxidant Supplementation Trial. Optometry. 2004;75:216-30.

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