Scientests have been able to produce a condition similar to the end stage of dry macular degeneration. Using genetically engineered mice that contain a retinal pigment epithelium, they showed these mice do not secrete vascular endothelial growth factor (VEGF).
Macular Degeneration is thought to result from the breakdown in the relationship between retinal pigment epithelium (RPE) and the vascular layer that nourishes the retina. It is thought that as the RPE degenerates it will not produce VEGF and that this results in damage to the vascular layer. As a result, dry macular degeneration will occur.
Conversely, if the vascular layer degenerations there is an over-production of of VEGF as the eye attempts to grow new blood vessels. This may result in the onset of wet macular degeneration.
VEGF molecules produces by the RPE must travel across the Bruch’s membrane to the vascular layer in the retina. In the research, the mice were only able to produce a type of VEGF that could not travel across this membrane, thus depriving the vascular layer of VEGF. In the genetically engineered mice however, the progressive degeneration resulted in a decline in visual acuity.
The researchers were quick to caution that continued blocking of VEGF through use of anti-VEGF drugs such as Lucentis may contribute to the development of late state dry macular degeneration.