Glasses for eyes that are sensitive to light: the options.

If you notice any change in your sight, see an eye doctor. The options below change how much light reaches your eyes.

A tinted lens lets through a set share of light. Sunglass lenses are sorted into five categories. Category 0 lets through over 80 percent. Category 4 lets through 3 to 8 percent.

The limit: the tint never changes. At night, or when it is hard to see, it also makes everything around you darker. Category 4 is not for driving. Lenses that let through less than 75 percent are not for driving in twilight or at night.

These are photochromic lenses. Most darken in the ultraviolet light of the sun, and not under lights indoors. The light sets the level, not you.

The limits: they take time. Most of the darkening takes about half a minute, and clearing takes about five minutes. Heat makes them less dark. A windscreen blocks much of the light that darkens them, so they do not go as dark in a car.

Electronic tint uses a layer that gets darker or lighter when an electric signal changes. Layers like this are used to control how much light passes through.

The limits: the layer needs electric power to change. And a whole pair is worn in place of the glasses you already own.