try this: make a pinhole in a lens sized piece of 3X5 card, or by folding up an index finger. look through it from a variety of angles or positions. some positions will provide a marked improvement of visual clority, cuz the light is focused on the least distorted portion of your lens-maybe enough to get by without the lens grinder.Reliance on spare lenses ignores the possibility of prescription change over time, which many of us with visual acuity issues experience annually.
But take it a step or two further. What if your infirmity is sleep apnea, and you need your c-pap machine-does one go into your bug out bag? Or maybe it's chronic renal failure, and you need hemodialysis 3 times a week? Do you teach yourself to do home peritoneal dailysis just in case, and toss 15 liters of sterile dialysis fluid in the bob? At what point do you accept the inevitability of death absent the support of a pretty sophisticated support system?