Lady developed dry eye (KCS) when she was about 11 years old. She has done really well with tear stimulators and artificial tears.
Yorkies can be born without lacrimal glands which means they don't produce tears. In this case, tear stimulators don't work.
Your vet can do a very simple test to see if Cooper is producing tears.
Here is a great article about dry eye:
KCS (Dry Eye)