On the Web - This is an excellent article by Dr. Gregory Mertz DVM discussing how to identify and treat this eye problem in leopard geckos.
Winking Geckos: The Eyelid Geckos of the World
The Reptile Report - Where do they come from? How many kinds of eyelid geckos are there? Why can they blink when other geckos can’t? As their name implies, eyelid geckos are the only geckos in the world that retain movable eyelids. Mostly ground dwelling in nature, these lizards lack the specialized toe pads found in other geckos. The combination of movable eyelids, terrestrial habits, unspecialized feet, and a variety of other skeletal characteristics mark eyelid geckos as among the most primitive geckos in the world. In addition, although eyelid geckos are found around the globe, species remain remarkably similar to one another in form and habit, further suggesting that they are an old group and that remaining species are but twigs of a very ancient and highly branched family tree. Scientists are still struggling with eyelid gecko taxonomy.@ the online source