Note this clinical scenario: A 70-year-old man presents for an eye exam. He is noted to have a few small macular drusen and best-corrected vision of 20/20 in each eye. He is followed annually by the same doctor for 20 years with a take-home Amsler grid. The only changes noted throughout the years are a slight increase in the number of drusen with no decrease in visual acuity; Amsler grid testing is always negative. A few months after his last annual exam, at age 90, he notices at home that the vision in his right eye is blurry” when watching TV, but he thinks he is developing a cataract like his friends. He thinks he will wait until his next annual exam; he has misplaced his Amsler grid; he hates being dilated.
Three months later, the vision decreases markedly and even though it wasn’t time for his annual exam, he thinks he ought to see his eye doctor because the “cataract” must have gotten a lot worse. To his surprise and dismay, his eye doctor tells him he has developed the wet form of macular degeneration and the amount of bleeding in the back of his eye is so great at this point that nothing can be done (Figure 1). He eventually develops a scar and finger-counting vision (Figure 2). This was especially frustrating because the patient was the eye doctor’s own father. Remarkably, he lives to over 100 years, complaining for the last decade of his life about the dark blind spot right in the center of his vision.
Years later, this eye doctor learns of a simple genetic test for patients with signs of age-related macular degeneration (AMD) that involves taking a sample from the inside of a patient’s cheek using a brush. The sample is analyzed within a few weeks to determine if a patient has certain high-risk alleles that will increase the risk of lifetime progression to a more advanced form of AMD and thereby, along with smoking history, is used to determine a risk category and frequency of follow-up.
The risk categories range from one to five. A risk category score of one or two means that the patient is at no greater risk than the general population to progress to a more advanced form of AMD and could be followed every six months to a year. A risk category score of three, four, or five means that the patient is at a higher risk than the general population to progress and should be followed more frequently, perhaps every three to four months. The eye doctor decides to test this now 90-year-old patient who was followed for the past 20 years. The results indicate a risk category score of four, which meant that this eye doctor would have followed this patient every three to four months (had this information been available at the time) and not just once a year. It is likely that the patient’s wet AMD would have been detected much earlier, and his vision might have been easier to save because by the time this patient developed choroidal neovascularization (CNV), effective clinical intervention was already available.
AMD is the leading cause of irreversible blindness in people over 55 in the developed world. Of the estimated 9.1 million people who have AMD in the U.S., approximately 1.75 million people have late-stage disease and another seven million are at high risk of developing advanced disease.1 About 90 percent of patients with AMD exhibit the dry, atrophic form of the disease, for which there is currently no clinical intervention, with the exception of the Age-Related Eye Disease Study (AREDS) formulation which reportedly reduces risk to advanced AMD by 25 percent in patients with intermediate AMD. About 10 percent of affected patients with AMD develop CNV, which is responsible for 90 percent of severe vision loss. The potential for vision loss from all forms of AMD increases if the disease is undetected, untreated, unsuccessfully treated, or inappropriately treated.2