Bacterium present in eyes with ‘wet’ age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of blindness in Americans over the age of 55. The majority of vision loss is due to neovascular AMD, the advanced form of the disease characterized by the formation of blood vessels in the macula, the center part of the eye’s retina. These blood vessels often leak, thus giving neovascular AMD the name of “wet” AMD.

Researchers at the Massachusetts Eye and Ear Infirmary (MEEI) have found that chlamydia pneumoniae, a bacterium linked to heart disease and capable of causing chronic inflammation, was present in the diseased eye tissue of five out of nine people with “wet” AMD. However, it was not found in the eyes of more than 20 individuals without AMD, providing more evidence that this disease may be caused by inflammation. The study is described in the November 2005 issue of Graefe’s Archive for Clinical and Experimental Ophthalmology.

“The paper showed that C. pneumoniae is capable of modifying the function of important cell types involved in regulating normal eye function,” said lead author Murat Kalayoglu, MD, PhD. “We found that C. pneumoniae infection led to increased production of vascular endothelial growth factor (VEGF), the key protein involved in wet AMD. That C. pneumoniae infection of human eye cell types increases VEGF production is therefore significant and could explain in part why VEGF levels are increased in many people with wet AMD.” Kalayoglu is a Harvard Medical School research fellow in ophthalmology at MEEI.