Article Date: 2/1/2011

Addressing AMD Early

Addressing AMD Early

A more aggressive approach to diagnosing and monitoring AMD can afford better outcomes for patients.

Kirk Smick, OD: Like other primary care optometrists, I've been asked to assume a more active role in the management of age-related macular degeneration (AMD). We need to digest a great deal of new information, including how to incorporate new tests and concepts into private practice. More than ever, we've become partners with specialists in diagnosing, treating and following these patients. Gone are the days when we could detect and refer.

For this roundtable discussion, we've assembled other optometrists with experience in this emerging area of care. They will share their practice-based advice on a variety of issues. Our first topic will be the importance of making an early diagnosis.

Why an early diagnosis?

Dr. Smick: In my one-location practice in Atlanta, 11 eyecare practitioners see about 250 patients each day. A retinal surgeon comes in 2 days a week. Ten years ago, we could refer a patient without consequence long after a choroidal neovascularization (CNV) had formed. Why is it so important to make the diagnosis earlier now?

Jeffrey Gerson, OD: I receive many referrals from colleagues. I find that more patients are at risk for developing AMD and many are experiencing early, intermediate or advanced stages of the disease. It's crucial to identify patients with early AMD so we can try to prevent the formation of choroidal neovascular membranes (CNM). We also need to detect wet macular degeneration as soon as possible.1 Once a patient develops CNM, we know the outcome will be better if we begin treatment early.2,3

Steven Ferrucci, OD: Today our patients can benefit from many treatments, including bevacizumab (Avastin, Genentech), ranibizumab (Lucentis, Genentech), photodynamic therapy (PDT) and combination treatments, such as ranibizumab and PDT or ranibizumab with intravitreal steroids.4-7

But we also have new and improved diagnostic technologies, such as optical coherence tomography (OCT), scanning laser polarimetry (GDx, Carl Zeiss Meditec), the Heidelberg III retinal tomograph (HRT) and the Foresee preferential hyperacuity perimeter (PHP) from Reichert, which has been shown to help make an early diagnosis.8

When I was a resident, we didn't have treatment options for AMD. An Amsler grid was fine for diagnosis because it didn't matter if the diagnosis was late or early. There was nothing we could do. Now, there is plenty we can do. As the chief of optometry at the Sepulveda VA Medical Center, I serve a geriatric population that benefits significantly from early diagnosis and treatment.

Diana Shechtman, OD: At Nova Southeastern University, where I'm an associate professor, we have access to all of the latest technology. With the advent of anti-VEGF treatment and potential of visual improvement, we've raised the bar, creating an expectation of good outcomes. A CNV of 3000 microns is unquestionably associated with extensive destruction and noticeable vision loss or visual disturbances but at this time, it may not carry a good prognosis following treatment. We need to identify earlier conversion from dry to wet AMD, when the patient still has good visual acuity. Early diagnosis leads to prompt treatment and better visual prognosis.

Dr. Smick: How many patients with dry macular degeneration eventually develop CNV or wet macular degeneration?

Dr. Ferrucci: Studies indicate that 10% to 20% of patients with dry AMD eventually progress to the wet form, which is responsible for most of the estimated 1.75 million cases of advanced AMD in the United States.9,10

Dr. Smick: Does everyone on this panel agree that we can't always see when changes have begun simply by looking at the macula clinically when these patients have 20/25 vision?

Dr. Gerson: I agree. The clinical examination is a crucial first step, but advanced technologies are often needed to detect very subtle findings that can aid in diagnosis.

When dry AMD converts to wet

Dr. Smick: When do AMD patients convert from dry to wet AMD? How can we recognize this change in a timely manner?

Dr. Shechtman: If a CNM grows 20 microns a day, that means it increases by 600 microns per month. If you follow up every 3 months, you increase the potential to identify a conversion much earlier on. Such a patient should be treated with urgency.

Dr. Smick: So 6 months is too long to wait?

Dr. Ferrucci: I believe it is too long. Studies have shown that lesion size is the number one prognostic factor for patients who will respond well to treatment.11-14 As we've discussed, the sooner we refer these patients for treatment, the better off they'll be. We need to check for changes in both structural and functional vision.

Dr. Gerson: I always try to identify these patients before their vision changes. It is critical.

Dr. Shechtman: We should also be aware of the potential to identify functional vision loss. The Foresee PHP can aid in detecting functional vision loss associated with the conversion of intermediate AMD to wet AMD. It has been clinically validated to be both sensitive and specific.

Dr. Smick: Based on what the panel is saying, early detection means within 3 months of CNV formation, when changes are difficult to see during a clinical exam. The patient may still have excellent vision. What changes in a patient with dry macular degeneration indicate that it's time to increase the frequency of monitoring?

Dr. Shechtman: Once I see structural changes, such as those associated with retinal thinning, pigmentary changes, drusen (in particular soft drusen), which is beginning to coalesce, then I believe the patient needs to be seen more often. Metamorphopsia, visual complaints or any functional change, such as decreased contrast sensitivity, also indicate a need for increased monitoring.

Testing contrast sensitivity

Dr. Smick: Is it realistic for the busy primary care practitioner to do contrast sensitivity testing on these patients?

Dr. Shectman: I think we should consider performing contrast sensitivity testing for patients with AMD. I've seen patients with 20/20 visual acuity and severe retinal thinning, as visualized through an OCT. If you assess contrast sensitivity, you may get a better sense of visual function, which can affect their everyday lives, even if they have no complaints of vision loss.

Dr. Smick: The Amsler grid has long been the gold standard for testing. What role does it play today in this disease process?

Dr. Ferrucci: I frankly don't like using the Amsler grid. Patients don't even use it. Or, if they do, they don't report changes until it's too late, which has been confirmed in studies.15 The grid is also not sensitive enough to pick up the early retinal changes of AMD or other conditions.

Finally, it's important to note that PHP has already been shown to have greater sensitivity than the Amsler grid in the detection of CNV among patients over 50 years of age.16 I give patients an Amsler grid but I don't expect much from the test. We are fortunate to have newer technologies to help recognize potential problems.

When I was a resident, we didn't have any treatment options for AMD. An Amsler grid was fine for diagnosis because it didn't matter if the diagnosis was late or early. There was nothing we could do. Now, there is plenty we can do.

—Steven Ferrucci, OD


References
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Optometric Management, Issue: February 2011