Study: Is AMD underdiagnosed in primary care?

Primary eye care providers are often the first line of defense against sight-threatening disease; however, a new study suggests America's leading cause of vision impairment in older adults might be going underdiagnosed.

Published in May's JAMA Ophthalmology, the study found that 25% of eyes deemed normal by primary care ophthalmologists and doctors of optometry after a dilated eye examination had characteristics of age-related macular degeneration (AMD) upon closer look. Such results reveal just how underdiagnosed AMD may be, further underscoring the challenges of early detection and the necessity for routine eye care.

To examine this prevalence, researchers conducted a cross-sectional study of primary eye care practices in Birmingham, Alabama, and collected data on 644 people (1,288 eyes) over 60 years of age with normal macular health recorded on their most recent dilated eye examination. Upon review using the Clinical Age-Related Maculopathy Staging system based on color fundus photography and masked grader, 968 eyes were confirmed to have no AMD. However, among eyes with AMD that went undetected:

• 249 had small drusen.
• 250 had intermediate drusen.
• 96 had large drusen.
• 43 had hypopigmentation.
• 32 had hyperpigmentation.

These subjects with undiagnosed AMD were more likely to be older and male with less than a high-school education, study authors note, and older eyes were more likely to present with drusen of all sizes. In particular, large drusen made up 30% of undiagnosed eyes, "indicating these patients would have been candidates for therapeutic intervention with nutritional supplements; however, only 3 of 99 eyes with intermediate AMD were from persons taking AREDS formulation nutritional supplements," the study notes.  

Although researchers write that ophthalmologists and doctors of optometry were equally likely to miss an AMD diagnosis, advances in retinal imaging technologies could eventually help stem the prevalence of undiagnosed AMD as equipment becomes more affordable for the primary care setting.

AMD in retrospect  

Estimated to affect 1.8 million Americans with another 7.3 million at substantial risk for vision loss, AMD is the leading cause of severe vision loss in adults over 50, according to the Centers for Disease Control and Prevention. AMD takes two forms: atrophic (dry) and exudative (wet), the former occurring more commonly but having no known cure. Although any central vision lost to dry AMD cannot be restored, there is a link between nutrition and AMD progression. Such dietary changes and nutritional supplements, such as AREDS, can slow vision loss.  

Elizabeth Wyles, O.D., primary care educational coordinator at the Illinois College of Optometry, says this study is particularly interesting in that it quantifies exactly how underdiagnosed dry AMD is in a sample population.  

"I think like any early disease process, there are many patients that are probably underdiagnosed by clinicians," Dr. Wyles notes. "I think most optometrists would agree that there are likely early cases of glaucoma, corneal degeneration, amblyopia or other problems that go undetected daily until they produce more signs and symptoms. Technology has made it easier to diagnose some of these problems earlier."  

Access the AOA's clinical practice guideline, Care of the Patient with Age-Related Macular Degeneration.