Thank you for sending the update. I read your reply and quite literally scrunched up my face and said, "Hmmm."
The involvement of other facial muscles makes me open my mind to considering the possibility that this isn't just an eye issue, but perhaps a neurological issue.
Facial tics are not common in dogs, but can occur. They can be the result of infectious diseases, toxins, and other neurologic disorders.
I'm not certain if you're open minded about such things, but - as someone who is trained in tradition Western medicine - I can see a place for "alternative" therapies with a situation like this, that is... if diagnostic testing and therapeutic trials for infectious diseases (like those mentioned above) don't produce any results.
When you treat the "whole patient" instead of the problem in cases like this, it's not unusual to get a response. TCM (Traditional Chinese Medicine), acupuncture, laser... these are tools that I would not hesitate to reach for in a case like Lincoln's if I couldn't identify the cause through traditional medical approaches.
The place to start, though, is with a thorough physical examination, including an ophthalmic exam, and baseline blood work to look for any abnormal findings that could be related... especially electrolyte abnormalities (can cause tremors), and evidence of infectious diseases.
Is Lincoln still acting fine otherwise?