The next time Turbo is taken to be groomed or to the vet get them to check that there are no hairs growing in towards the eyes. If there are none, you can get some stuff called Angel Eyes which stops any tear stains. If the eyes themselves are watering you can use Optrex (same as the human variety).
Kisses to Turbo, I sometimes handle a Shih Tzu for a friend at dog shows. One is called Tia, and there is also Dolly, Queenie and Lacey. I was there when Queenie was born as the owner had never bred a litter before. You would not have known they were Shih Tzus, they looked like tiny Jack Russells because they have short hair when born.