What Causes Numbness In The Thumb?

My left thumb has been feeling like vague needles and pins and partially numb now for 2 wks, and I wear progressive lens with bifocals and I've noticed that I am not seeing as clearly as I usually do.

What do you think could be causing this, I also have essential tremors but I don't ever remember not having this.
I am a 46 years old female, thank you.