Diabetes is the leading cause of blindness for people under 65. So far, physicians have only been able to use surgery to slow the damage. However, at Pennsylvania State University, biologist Theodore Hollis and ophthalmologist Thomas Gardner have discovered how diabetes causes blindness--and how it might be prevented. The researchers found that blood vessels in diabetics' eyes produce histamines, substances that make the blood vessels leaky and that are involved in allergic reactions. Damage to the retina, the researchers suspect, is a long-term effect of the histamines and of the fluids that leak out of the blood vessels.
The discovery suggests that prescribing antihistamines, commonly used to fight allergies, may prevent diabetic blindness. The Penn State researchers first showed that such drugs prevent blood-vessel leaks and eye damage in rats. And preliminary results of a six-month trial using antihistamines on 14 patients look promising. "If it is conclusive, then we can proceed with a larger clinical trial," says Gardner.