That might not make sense... unless you own a pair. Shields would be a better term. Basically, they are like sunglasses (usually non-prescription) with clear lenses. In the mountain biking world, I've often found them very useful. I've used them most on night rides in mud. If you've ever caught a glob of mud in the eye on a fast singletrack descent, you'll know just how useful they can be. Other obstacles that can ruin a ride include, but are not limited to: branches, dirt, dust, and bugs.
Ah bugs. It is of this that I want to particularly make mention of today. This morning, the ride was on the road (another great ride on the Synapse). The ride started out early--about 15 minutes before the sun came out. Wisely, I decided to grab a pair of clear shields (Rudy Project Maskerynas) on my way out the door. As we left my neighborhood, we headed west down to the lake to follow a road around its shores. It was beautiful. The sun was just beginning to light up the sky above the mountains to the east when it happened.
Bugs. BUGS! Tiny bugs, impossible to see in the early light of dawn, swarming around us. I could hear them hitting my helmet and glasses. I could feel them pelting my arms and face. I could--shudder--taste them. Then I glanced over at my friend riding next to me, trying to contort his face in such a way as to keep the bugs out of his eyes, while still being able to watch where he was going. A slow, bug strewn smile worked its way across my face. Yes, clear shields are important to road cycling as well. I don't think I'll ever ride at dawn or dusk without them.