Article Date: 9/1/2007

Early Glimpse Into AMD
instrumental strategies

Early Glimpse Into AMD

Uncover AMD risk years or even decades before disease onset.

LLOYD SNIDER, O.D.

Age-related macular degeneration (AMD) affects approximately 25 to 30 million people in the Western world, according to AMD Alliance International data.

Further, in the United States alone, this sight-threatening disease affects more than 1.75 million people, and this number will increase to almost three million by the year 2020, as a result of the rapid aging of the U.S. population, according to the National Eye Institute.

We, as eyecare practitioners, can help prevent this looming epidemic, however, by assessing the macular protective pigment density (MPPD) in our healthy patients and educating these patients about supplements that could help prevent disease onset. This is where the MacuScope, from MacuCheck, comes in.

A glimpse of the future

The MacuScope can uncover risk for the disease years or even decades before any signs (drusen) or symptoms (blurred vision) may appear. Specifically, the device measures and monitors a patient's macular protective pigment density (MPPD), also known as macular pigment optical density (MPOD).

Numerous studies on patients with and without AMD have revealed that a low MPPD is a major risk factor for the development of the disease.1,2,3

The macular protective pigment (MPP) resides in the macula, anterior to photoreceptors and the retinal pigment epithelium (RPE). It's made up exclusively of three carotenoids; lutein, meso-zeaxanthin and zeaxanthin, which give the macula lutea its yellow coloring. This unique collection of carotenoids is only found in the center of the macula and nowhere else in the body. They protect the delicate macular tissue beneath the MPP by filtering harmful wavelengths of high-energy blue light, participating in active transport across cell membranes and via their extremely highly antioxidative properties.

MacuScope
HEIGHT: 16"
WIDTH: 11"
LENGTH: 20.5"
WEIGHT: 40 lbs.
FOOTPRINT: 11" X 20"
COST: $19,500.

Determining risk

The MacuScope test involves measurements in two areas of the macula: foveal, where the MPP is present and parafoveal, where there is no MPP (a reference point). For the foveal test, the patient looks through the device's eyepiece (dilation is unnecessary) and fixates at a central crosshair target that overlays a small circular area. Here, heterochromatic flicker photometry occurs (blue light [460nm] alternating with a green light [540nm] that causes the circular area to pulsate or flicker). The patient informs the operator when the pulsation stops or minimizes (null point), revealing a match in luminance of the alternating blue and green stimuli. The measurement is recorded in units of absorption. For the parafoveal test, the patient fixates on a peripheral fixation target located 8° to the right or left (depending on the eye being tested), from the center fixation target and uses his peripheral awareness to determine the null point.

Many patients note a darkening of the blue light at the null point. Since the 460nm light is only absorbed by the centrally located MPP, the difference between the foveal and parafoveal measurements is due exclusively to the MPP's blue-light absorption.

A printout shows the two measurements and the calculated difference, which is the patient's MPPD. The instrument also grades the calculated MPPD against a normative database to determine the patient's AMD-development risk.

Preventative care

If the patient has a low MPPD or a low-average MPPD coupled with other AMD risk factors, such as family history, smoking, hypertension and/or cardiovascular disease, hyperopia, obesity, light-colored eyes and skin or female sex, we prescribe a supplement that contains all three carotenoids (lutein, meso-zeaxanthin and zeaxanthin). We explain to these patients how the supplement is necessary to increase their MPP and may reduce their risk for developing AMD.4

Thus far, our patients have been very compliant with these supplements. As a result, we've measured increases in MPPD at six-month follow-up evaluations. OM

  1. Beatty S, Murray IJ, Henson DB, et al. Macular pigment and risk for age-related macular degeneration in subjects from a Northern European population. Invest Ophthalmol Vis Sci. 2001 Feb;42(2):439-46.
  2. Bone RA, Landrum JT, Mayne ST, et al. Macular pigment in donor eyes with and without AMD: a case-controlled study. Invest Ophthalmol Vis Sci. 2001 Jan;42(1): 235-40.
  3. Delacourt C, Carriere I, Delage M, et al. Plasma lutein and zeaxanthin and other carotenoids as modifiable risk factors for age-related maculopathy and cataract: the POLA Study. Invest Ophthalmol Vis Sci. 2006 Jun;47(6):2329-35.
  4. Bone RA, Landrum JT, Cao Y, et al. Macular pigment response to a xanthophylls supplement of lutein, zeaxanthin and meso-zeaxanthin. Nutrition and Metabolism on-line journal. 2007 May 11;4:12.

LLOYD SNIDER, O.D., IS IN PRIVATE GROUP PRACTICE AT BIRMINGHAM VISION CARE IN BLOOMFIELD TWP., MICH. HE IS THE DIRECTOR OF OPTOMETRIC SERVICES AT MACUCHEK. E-MAIL HIM AT LLOYD@MACUCHEK.COM.



Optometric Management, Issue: September 2007