There are a myriad of trifocal lens types on the market. I use a Varilux type myself. With proper fit, one can see all three distances in a natural manner. Still doesn't help overhead.
I found if one gets his prescription fitted "low," i.e., so the spectacles can be worn low on the nose, one can look at the overhead panel over the tops of the spectacles, without another "add" (what optometrists call the lens inserts observed in bi-or tri-focals) on the top of the lens.
There were some spectacles which did indeed have another "add" on top. They were jokingly called "Airbus lenses," since apparently the need for them in pilots was realized by the introduction of the Airbus into service.
E-mail me at
[email protected], and I'll send you information about the several types of trifocal lense options.
Pilots have to see three distances-infinity (out the windscreen), a middle distance (the instrument panel), and "near,"(usually the approach plate holder, but now, vexingly, also the overhead).
The USAF school of medicine kept measurements for the three distances for each of their aircraft types at one time. So did Air Canada, I believe.
Now, if you didn't have to try to fly the sim with a full-face smoke mask, life would be a lot easier!