A drug to tackle two of the leading causes of blindness is a step closer after successful experiments in mice. Activating a specific protein in the eyes prevented blood vessel damage which can cause sight loss. The research has implications for macular degeneration and diabetic retinopathy - two common conditions associated with blood vessel problems. The University of Utah study, published in Nature Medicine, could also provide clues for treating other diseases. Both of the types of eye problems are common in older people, and involve both leakage of blood vessels within the eye, and the formation of abnormal new blood vessels. Researchers had already identified a protein called Robo4, which appeared to play an important role in the development of stable, working blood vessels. The proteins were activated in mice bred to mimic the effects of age-related macular degeneration (AMD) and diabetic retinopathy. The scientists saw that the blood vessel damage was prevented, or in some cases, reversed. While this does not prove that the same principle works in humans, or that a drug could be developed to harness this without side-effects, the researchers described the work as a "major breakthrough". Professor Randall Olson, director of Utah's John A Moran Eye Center, said: "We are excited about taking this opening and moving the frontier forward with real hope for patients who have but few, often disappointing options." The scientists believe that it will still take some years before a working drug can be provided for patients. Dr Hemin Chin, from the US National Eye Institute, said: "Given that vascular eye diseases, such as age-related macular degeneration and diabetic retinopathy, are the number one cause of vision loss in the US, the identification of new signalling pathways that prevent abnormal vessel growth and leakage in the eye represents a major scientific advancement." However, researchers in other fields are excited by the possibilities offered by Robo4. The damage caused by many other conditions, including serious infections such as SARS, are the result of damage to blood vessels. Cancer scientists are already investigating ways to use the protein presence on the surface of tumours to help target drugs. Among those is Professor Roy Bicknell, from the University of Birmingham, who was one of those who discovered the Robo4 gene in humans in the 1990s, originally naming it the "Magic Roundabout" gene. He said he was "very excited" by the research: "If this can really fix these eye conditions, then it is a big achievement. "I thought when I found this that this was going to be really big, and that appears to be the case." Source: BBC