There are variable-focus bifocal lenses that do work. They're called SmartSegs here in the US. They're a traditional bifocal lens with a line, but the bifocal segment is a variable focus, changing from about 3 or 4 feet at the top to maybe 18 inches at the bottom. Peripheral vision is unaffected, as the part outside the bifocal is the same as the top of the lens, and there is no blurry part. I've been wearing them for years, and I love them. Changing focus is simply a matter of moving your head very slightly. They work just like regular bifocals, but better. I was comfortable with them as soon as I put them on.
I have titanium memory-metal frames, with very thin wire temples, and they don't affect the noise attenuation much, if at all, and they're comfortable under the earseals, unlike most I've tried in the past. I can easily don a helmet while wearing them, and actually prefer that.