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

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

It would be unusual to have juvederm still in the lower lids after 4 years.  But if you have had a bluish tinge to the skin this whole time, it could be the Tyndall effect.  Any reason why you didn't go back and take care of this before?   If it is juvederm you can dissolve it with some hyaluronidase.  So it would be worth doing that.  If it isn't juvederm, you won't see any difference and will than have to explore other options.  Pictures are always helpful so we can see more of what bothers you!