Macular corneal dystrophy (MCD) is a hereditary disease that can affect middle-aged Labrador Retrievers. Affected dogs will develop cloudy eyes, due to an abnormal accumulation of glycosaminoglycans (carbohydrates) in their corneas (the equivalent to the windscreen of the eye). The disease is progressive, and although not painful, can cause marked visual impairment in affected dogs. The only treatment for the disease in people is surgical (corneal transplant), however this has not yet been performed successfully in the dog for the treatment of canine MCD.