WordWeb Online

1. Having very keen vision
   "quick-sighted as a cat";
   - argus-eyed, hawk-eyed, keen-sighted, lynx-eyed, sharp-eyed, sharp-sighted
    
2. Keenly perceptive or alert
   "quick-sighted into the faults of the time";
   - sharp-sighted, sharp-eyed

See also: perceptive, sighted