Flying Class III individuals (other than boom operators and individuals required to perform scanner duties) have no standard for depth perception/stereopsis IAW AFI48-123. I can't comment on the FAA's exact reasoning, although the areas of most concern to the military are aerial refueling and formation flying, both of which are uncommon in civil aviation. The FAA is willing to certify airmen with no depth perception, in fact, they don't mind if you are monocular. For a discussion of the FAA standards on depth perception, see the following link: http://www.faa.gov/avr/aam/Game/Version_2/03amemanual/WEB/Chapter 3/3.31-34.htm