Latanoprost is the first of a new class of drugs based on a natural chemical called prostaglandin, which helps the eye drain off its fluid. They also had significantly fewer side effects. And it is apparently not a reversible change even when patients stop taking the drug. The question is whether the change is cosmetic or dangerous. The company theorizes that Latanoprost increases the amount of melanin in people's eyes.
Melanin is a chemical that gives people skin color, and everybody's eyes have some.
But lighter-colored eyes don't produce as much of the pigment, allowing light to better diffuse through the eye and reflect back. The company gave high levels of Latanoprost to monkeys for a year and counted the number of melanin-producing cells, finding no increase. But these cells were producing more of the kind of melanin that causes a dark color than the kind that causes yellow colors. But critical panelists asked whether the melanin-producing cells would eventually get so full that they burst. Black glaucoma patients naturally have more eye pigment, and nobody knows how their eyes would be affected.