Had Juvederm injected in my tear troughs 4 years ago & was left with blue "tyndall stripes". Does this effect ever go away?

At this point it is much more likely that you have a blue hue for some other reason than Juvederm. However, hyaluronidase can dissolve some of the Juvederm if that is what it is, and most doctors don't charge for that.

Its unlikely but still  possible that the Blue hue is from your juvederm injections 4 years ago. I would reccomend that you have an assessment done by an expert injector and if it is juvederm a dissolving agent can be inject to dissolve the product.

It is highly unlikely that you have Tyndall effect at this point. You likely are seeing the vascular hue of the orbicularis muscle.  In addition you are likely experiencing protrusion of the orbital fat pads causing the shadowing you describe.   Visit with a board certified facial plastic surgeon, plastic surgeon or occuloplastic surgeon to discuss your options