You guys calling the original guy an idiot are all wrong. I'm a huge horse racing fan, and racehorses wear blinkers. A carriage-pulling horse, or a jumper, wears blinders, but the hoods that some racehorses wear are indeed blinkers, which is where the term comes from.
Horses wear blinkers. It stops them getting startled by movement in the peripheral vision. So to be described as blinkered means you are not open to other ideas, Single minded. Blinkered!