Original equipment material (OEM) suppliers started to add ultra violet resistant (UV) coating to the surface of the lens in an attempt to reduce this condition and prolong the usable life of the lens. This protective coating is very thin (25 µ (microns or 1 Mil)

Removing oxidation or scratches from vehicle headlights or brake lights (also polycarbonate) also removes the OEM ultra violet protection, which prematurely decreases the durability of the lens. Surfaces that have yellowed are a sign that the ultra violet (UV) sacrificial coating has failed and must be resurfaced and recoated.

"Headlight Restoration" - http://www.autopia.org/forum/autopia-detailing-wiki/141706-headlight-restoration.html#post1506615

Yes as stated above there is a coating and yours is starting to peel. My suggestion is to have a pro detailer wet sand and polish them back to clear. It's certainly something that you can do on your own if you are comfortable with it, but requires a buffer to do it correctly.
Then to keep them that way you should have a chemical based polish on hand like a paint cleaner and every few months polish them lightly and they will stay clear and clean. My 96 Camry lens are perfect.

Thanks all. I did some reading last night and I gave it a try this morning. Amazing what a wet sand and polish does!

Good job, not many are comfortable with wet sanding