DIAGNOSTICS

Managing AMD

How technology impacts risk assessment, prevention and patient education.

Pamela Lowe, O.D., F.A.A.O.

As primary eyecare practitioners, we are on the frontline for educating the public on conditions that can rob them of a lifetime of healthy vision. Of the ocular diseases we address, the one that can be most debilitating and aggressive is age-related macular degeneration (AMD). Through quality patient education, we can effectively manage patient expectations and help calm the fears associated with AMD.

As the name of the disease suggests, the greatest risk factor for AMD is age. Studies have shown that middle-age patients have a 2% risk of acquiring AMD, but the risk increases to nearly 30% in those older than age 75.¹ AMD causes 54% of all cases of blindness in patients older than age 40.² With the American population of baby boomers aging (those born 1946 to 1964) and their life expectancy increasing, we potentially face an epidemic number of patients who could suffer from this condition. As a result, it's imperative we educate the majority of our adult patients about this condition.

Risk factors and education

Our AMD educational process begins the moment we identify a patient as being at a high risk for AMD. The earlier we can identify risk factors in patients, the better we can educate them on how to prevent or reduce the severity of this disease.

Risk factors include race (Caucasians being at greatest risk); family history; gender (females at greatest risk); ultraviolet exposure; smoking and obesity.

Also, studies have shown that a low amount of macular pigment can put patients at high risk for vision loss from AMD. To identify this risk, our practice uses heterochromatic flicker photometry (HFP), which measures macular pigment optical density (MPOD).³

As Caucasian females are at greatest risk, we recommend HFP testing routinely for all Caucasian females age 21 and older, as well as other high risk patients — that is, those with two or more AMD risk factors.

I educate my patients that while they cannot change their gender, ethnicity or family history, they can reduce their risk of developing AMD by:

► stopping cigarette use

► limiting exposure to the sun

► losing weight

► exercising

► maintaining normal blood pressure

► altering diet

Through dietary alterations, patients can improve a low MPOD score. Diets consisting of foods rich in antioxidants (fish and green, leafy vegetables) and/or consumption of nutritional supplements have been shown to be beneficial in reducing the severity of AMD. We have found that HFP not only identifies patients who can benefit from vitamin supplementation, but as importantly, it tracks those patients on high dose supplements to monitor improvements to their level of macular pigment, which reduces their risk for AMD. In my practice, patients increased their pigment levels as high as 43%; the majority of my patients increase, on average, from 10% to 20% during the first six months of using high-dose supplements.

Preventing CNV progression

Once we detect dry AMD, we educate the patient and all caregivers on what the disease entails. It's important to discuss methods to monitor and prevent the progression of choroidal neovascularization (CNV). We tell patients that the closer we monitor possible conversion, the more likely we are to prevent vision loss at earlier stages.

It has been well documented that patients with clinical signs of dry AMD can, at any time, convert to the more aggressive wet AMD. In fact, 80% of advanced AMD cases are due to CNV. Development of CNV can happen very quickly with lesions growing 20 microns per day.⁴ As clinicians, we aren't diagnosing these lesions soon enough, and by the time a patient detects functional changes, vision loss has already occurred.

Our practice uses the preferential hyperacuity perimeter (PHP) to manage patients who have known, visible macular changes. PHP, the only FDA-cleared device to monitor conversion of dry to wet AMD, is a functional test using hyperacuity — the ability to perceive minute differences in the relative spatial localization of two or more visual stimuli.

PHP eliminates the inherent flaws of the Amsler grid (completion, fixation and crowding) and detects changes in the eye with 82% sensitivity and 88% specificity before the functional activity deteriorates.

Most practices pick up CNV conversion five and a half months after progression when the lesions are about 3,300 microns.⁵ We know from studies of anti-vascular endothelial growth factor (VEGF) treatments that early detection of conversion from dry to wet AMD leads to better therapeutic outcomes. PHP tracks changes in a patient's visual field resulting from AMD progression.

Continuing education

While in-office testing is essential, it's also important to educate patients at each visit. Web sites, such as the National Eye Institute, provide resources for patients and their caregivers (see www.nei.nih.gov/health/maculardegen/armd_facts.asp).

We explain that although no form of treatment can prevent vision loss when dry AMD reaches the advanced stage, treatment can delay and possibly prevent intermediate AMD from progressing to the advanced stage, in which vision loss occurs.

One such treatment is vitamin supplements. The initial Age-Related Eye Disease Study (AREDS) showed that high-dosed antioxidant vitamins and minerals can reduce the rate of advanced AMD by 25% and the risk of moderate vision loss by 19% through six years. The AREDS II study, currently underway, has added lutein and zeax-anthin (plant derived yellow pigments) along with omega-3 fatty acids (derived from fish oil) to the vitamin supplement.

Educating patients to manage risk factors gives them tools to take an active role in their own health, rather than relying solely on in-office procedures.

Expectations and fears

Because losing sight is one of the greatest fears of AMD patients, we must take the time to discuss all aspects of the disease and what to expect as their condition progresses. By detecting risk and progression, we can discuss appropriate expectations.

HFP helps us to present the possibility of the disease early, leading to a discussion of risk factors. By testing regularly to determine whether dry AMD is converting to wet AMD, patients know that we are proactively monitoring so as to catch progression and implement treatment before these patients experience significant vision loss.

We keep an open dialogue with patients and their caregivers regarding AMD. This dialogue allows us to provide patients with realistic expectations about their condition and, hopefully, alleviate fears. In our role as one of the leading primary eyecare practitioners, it's our responsibility to educate, diagnose and initiate prevention/treatment plans that ultimately lead to better visual outcomes for our AMD patients. OM

1. National Eye Institute. Age-Related Macular Degeneration. www.nei.nih.gov/health/maculardegen/armd_facts.asp. Accessed March 20, 2009.

2. Kempen JH, Mitchell P, Lee KE, et al. The prevealence of refractive errors among adults in the United States, Western Europe, and Australia. The Eye Diseases Prevalence Research Group. Arch Ophthalmol. 2004 Apr;122(4):495-505.

3. Nolan JM, Stack J, O' Donovan 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.

4. Vander JF, Morgan CM, Schatz H. Growth rate of subretinal neovascularization in age-related macular degeneration. Ophthalmology. 1989 Sep;96(9):1422-6; discussion 1426-9.

5. Olsen TW, Feng X, Kasper TJ, et al. Fluorescein angiographic lesion type frequency in neovascular age-related macular degeneration. Ophthalmology. Ophthalmology. 2004 Feb;111(2):250-5.

Dr. Lowe is currently director and president of Professional Eye Care Center, a private practice she founded in 1992 on Chicago's Northwest Side. She is an active member of the American Optometric Association, the American Academy of Optometry and the American Public Health Association.