Some two million people around the world suffer from a serious degenerative eye disease that literally has no treatment at all beyond "cross your fingers and hope for the best."

But if you're suffering from the gradual -- and ultimately total -- loss of vision that marks retinitis pigmentosa, you don't have to cross your fingers anymore.

New research led by Harvard University shows an easy way to stop this frightening condition in its tracks -- and it's not a new drug with side effects or an operation with risks.

It's an ordinary vitamin mixed with a little bit of fish.

Three clinical trials show that megadoses of vitamin A -- 15,000 IU a day -- combined with 0.2 grams a day of omega-3 fatty acids can slow the loss of vision by between 40 percent and 50 percent.

In real numbers, that could add up to an extra 18 years of vision.

The researchers don't know for sure why roughly two servings of fatty fish a week can have such a powerful impact on all that vitamin A, but they've got their eyes on one omega-3 fatty acid in particular: DHA.

Your retina is already loaded with DHA (which is why fatty fish -- not carrots -- is what you should be eating for good vision even if you're healthy). And in the case of retinitis pigmentosa, the researchers believe extra DHA is needed to help carry the vitamin A from the photoreceptor cells that have it to those that don't.

The result isn't a cure for retinitis pigmentosa, but it could dramatically change the prognosis.

Right now, someone with this condition can expect to go blind by the age of 60. With vitamin A and fish oil, that might be delayed until they're almost 80 -- or right around our actual life expectancy these days.

Since too much vitamin A can interfere with vitamin D and may even increase your risk of osteoporosis, don't try treating yourself on this one -- talk to your doctor about the best and safest way to raise your A levels.

And don't forget to add the fish oil -- because along with helping to slow retinitis pigmentosa, omega-3 fatty acids can also slash your risk of both the "wet" and "dry" forms of macular degeneration.