instrumental strategies

Assess AMD Risk

Device enables assessment of key AMD risk factor.

N. REX GHORMLEY, O.D., F.A.A.O., AND JACK J. YAGER, O.D., F.A.A.O.

Age-related macular degeneration (AMD) is the leading cause of blindness for Americans age 55 and older, with more than 10 million Americans currently grappling with the sight-stealing disease, according to the AMD Foundation. As a result, to prevent vision loss and preserve your patients' quality of life, you must accurately determine AMD risk.

QuantifEye, from ZeaVision LLC, helps you to do this. How so? It measures the density of the Macular Pigment — a key AMD risk factor — via heterochromatic flicker photometry.

Here, we explain why this is important and how, specifically, the device works.

Measuring MPOD

Macular pigment is a natural barrier, which protects the central retina from oxidative damage.^1,2 It's comprised of lutein and zeaxanthin — carotenoids — which demonstrate antioxidant activity and therefore keep the retina safe by filtering and absorbing high-energy, short-wavelength visible light. Researchers have discovered that oxidative damage plays a role in the pathogenesis of AMD.^3,4

In addition, researchers have linked many putative AMD risk factors, such as tobacco use, female gender, lens density, reduced visual sensitivity and light iris color, to a lack of MPOD.⁵ Further, research has revealed that a diet poor in antioxidant micronutrients (vitamin C, E, carotenoids, zinc) and low plasma levels of antioxidants may favor the development of AMD.¹

The good news: Data from clinical, epidemiological and experimental studies suggest that lutein and zeaxanthin may protect against the development of AMD. In addition, supplementation of these antioxidants appears to generate an increase of the density of the macular pigment.^3,6

QuantifEye's role

The QuantifEYE device uses heterochromatic flicker photometry to provide an MPOD (Macular Pigment Optical Density) value.

QuantifEye HEIGHT: 12 inches WIDTH: 9 inches LENGTH: 14 inches COST: Please contact ZeaVision for pricing information. QuantifEye utilizes a laptop computer, provided with the device, to present a graphic display of the patient's MPOD, as well as to provide data storage.

To obtain an MPOD measurement of the macula, the test provides the patient with varied frequencies and brightness of alternating blue and green light emitting diodes (LED) in the center of a white background. The macular pigment absorbs the blue, but not the green light. The green light acts as a reference for the device to create a graph demonstrating the absorption capabilities of the patient's MPOD. Instruct the patient to press a button when he begins to see flickering.

A peripheral measurement at 6° factors in the presence of yellowing media, such as the lens. Since this yellowing would be additive to the MPOD, it's necessary to remove it to obtain an accurate MPOD. To obtain the peripheral measurement, the patient looks at a red fixation light at 6° and presses the button when he sees, out of the corner of his eye, the center blue light flicker. The software then calculates the accurate MPOD.

The software also allows you to estimate the media yellowing (rather than doing the peripheral measurement) based on the patient's age. You must enter the patient's birth date into the instrument to initiate testing. The software utilizes the value obtained in the peripheral test or the value programmed into the software for the estimate and eliminates that additive yellowing from the media, leaving only the true MPOD value.

QuantifEYE provides MPOD measurements that enable you to categorize the patient as "Low," "Medium," or "High" in terms of AMD risk. You can use this data in conjunction with the patient's fundus exam results and other risk factors, such as family history, to determine the patient's overall risk of disease development.

Based on this information, you can decide whether supplementation or lifestyle changes, such as cessation of smoking, may benefit the patient.

You can then employ the device to track the progress, if any, from the patient's baseline MPOD.

Because QuantifEYE offers early risk assessment, it enables you to determine appropriate management to preclude vision loss and preserve your patients' quality of life. We've found that once we educate our patients on the importance of MPOD measurement in relation to AMD risk, they become compliant to our prescribed treatments. OM

1. Drobek-Slowik M, Karczewicz D, Safranow K. The potential role of oxidative stress in the pathogenesis of the agerelated macular degeneration (AMD). Postepy Hig Med Dosw (online). 2007;61:28-37.
2. Pauleikhoff D, Van Kuijk FJ, Bird AC. Macular pigment and age-related macular degeneration. Ophthalmologe. 2001 Jun;98(6):511-9.
3. Haddad WM, Souied E, Coscas G, Soubrane G. Macular pigment and age-related macular degeneration. Clinical Implications. Bull Soc Belge Ophthalmol. 2006;(301):15-22.
4. Nolan JM, Stack J, O'Donnovan O, et al. Risk factors for age-related maculopathy are associated with a relative lack of macular pigment. Exp Eye Res. 2007 Jan;84(1):61-74.
5. Beatty S, Koh H, Phil M, et al. The role of oxidative stress in the pathogenesis of age-related macular degeneration. Surv Ophthalmol. 2000 Sep-Oct;45(2):115-34.
6. Richer S, Devenport J, Lang. Last II: Differential temporal responses of macular pigment optical density in patients with atrophic age-related macular degeneration to dietary supplementation with xanthophylls. Optomety 2007 May;78(5):213-9.