Getting the correct prescription for shooting glasses for a cataract patient

I've been struggling in the past to get a proper prescription for shooting glasses for the front sight on a 1911.  Carrying the gun around to get my eyes checked didn't feel like the appropriate thing to do, so, I made up this gizmo.  Because my cataract surgery my eyes can no longer adjust their focus.  

I took an old mobile phone case, and angled it to match a 1911.  I attached a ruler to the case, using blue "painter's tape".  The far end of the ruler was the same distance from the "grip" as on the Les Baer I was trying to simulate.  At the end of the ruler, I taped a business card, bent at the end such that if I can see the text on the card sharply, my front sight will also be that sharp.

My goal is to hold this mock-up gun out in front of me, and have the optometrist determine the correct prescription. 

(I'm hoping that a prescription for the front sight distance on a 1911 will work well enough on shorter and longer guns.)

Creative!

Yep, another adaptation of the many ways it's been done. I just take my guns to the last appointment of a shooting enthusiastic optometrist.

I wanted the red dot round. I just took an air pistol in when I had my exam. Time to do it again I think.