they don't hurt light output...matter of fact they also help block out some of the glare from the hid cuz i noticed after i took out the eyelids there's some light shooting up on the wall that wasn't there before haha
When u say output u mean the beam pattern right? Actually on mine they do, but not to the point where its a major problem. I can still see at nite when I drive. Im going to install some fog lights pretty soon tho which I think should fix it. But again, its nothing big.
ditto to what everyone says..... ever since i put HIDs on, the glare was reduced a bit... oncoming traffic flashed their headlights less when they encounter me and my HIDs ..... however, lighoutput is not at all noticeably reduced when your driving since only the glare is reduced