Saltamontes:
Several years back I spent what seemed an eternity to tie on a Sulphur pattern at dusk. I attributed my problem to low light.
Sooooooo...
I bought a brighter light to use at night.
And...
It didn't make a difference .
Sooooooo...
I bought a pair of Hat Eyes to clip on my hat visor and now I can tie on anything at any time with any knot I want.
So IF you haven't tried magnification yet, give clip on magnifiers a whirl. It solved my problem and I fish a LOT at night.