While in remission now I have damn extensive experience with hemifacial/blepharospasms - while the precise mechanism is debated I would stake my soul on electrolytic disturbance of Mg2+ mainly, Ca2+ in a lesser role, throughout the optic nerve and constricted blood flow in the tiny vessels in that area.
Clear induction from: Meperidine, Loperamide, 4-AcO-Loperamide, EPD and Pseudo/Ephedrine IME, may have forgotten some.
As a thieno- I do wonder if Etiz induces more clinically significant metabolic changes than the prototypical BZD's.
Such changes are why I harp on about adequate hydration, nutrition and supplemented electrolyte levels - simple salts are the diesel powering your organic vessel, you try filling a tank with Pepsi and piss as opposed to topping up frequently....