
The GM can always Ctrl+L any token to see what that token sees, but the players don't have this option. If a player control multiple tokens, he or she will always see the sum of the sight of both tokens. If either token has "Darkvision", their vision will probably be bright - they won't be able to know how little the other token sees. Being able to Ctrl+L a token to see what only that token sees would be a good solution.