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AMD in Asians requires different diagnostic tools, treatments
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HONG KONG — Age-related macular degeneration in the Asian population requires different diagnostic tools and treatments than those used in Caucasians, likely because the disease develops on different genetic levels in the two ethnicities, a presenter said here.
 Wai-Man Chan |
"AMD in Asians may have different phenotypic or genotypic patterns," Wai-Man Chan, FRCS, explained during the AMD Alliance International session at the World Ophthalmology Congress. "We may postulate that there may be two genetic pathways."
Caucasians, Dr. Chan said, develop drusen from complement factor H, then express HTRA1. Asians are less likely to have complement factor H so their pathway bypasses the drusen and proceeds along the genetic pathway to HTRA1. This makes it difficult to diagnose early or categorize them as high risk and thus puts Asians at a 10 times greater risk of developing AMD.
"Drusen are less common in the Chinese or the Asian population. ... Even if they can be found, they're usually very small," Dr. Chan said. "If we can't identify the high-risk group, it seems that we may miss some patients with the high risk factors."
In addition, serosanguineous maculopathy affects Caucasians and Asians differently. Caucasians with this maculopathy have a 95% risk of developing AMD, making diagnosis easy with fluorescein angiography. Asians, though, have an 80% chance of the same progression, while 20% instead develop polypoidal choroidal vascularization (PCV), which requires indocyanine green angiography in order to visualize the polyps and make a diagnosis.
PCV not only responds differently to diagnosis methods, but also to treatments, Dr. Chan explained.
"AMD alone can be managed by anti-VEGF, with or without photodynamic therapy, but for PCV the baseline should be ... photodynamic therapy, but we can add on something, for example anti-VEGF or triamcinolone, to increase the visual outcome," he said.
While PDT causes a loss of visual acuity in traditional AMD, Dr. Chan showed that it improved visual acuity for PCV patients, although the underlying edema was not resolved and there were still problems with bleeding.
This resolution was found with the combination treatment of PDT with triamcinolone and ranibizumab, he said. But anti-VEGF monotherapy did not resolve the persistent polyps in PCV patients as well as photodynamic therapy did, Dr. Chan said.
He said he is looking forward to a more formal study in the future.