1. Mary M. and Sash A. Spencer Center for Vision Research, Byers Eye Institute, Stanford University, Palo Alto, CA, USA
2. College of Information Science & Technology, University of Nebraska Omaha, Omaha, NE, USA
3. Kentucky Lions Eye Center, University of Louisville, Louisville, KY, USA
4. Mary M. and Sash A. Spencer Center for Vision Research, Byers Eye Institute, Stanford University, 2370 Watson Court, Suite 200, Palo Alto, CA 94303, USA