slab offs

[eddietz3]

under what conditions is a slab off required for a patient wearing single vision lenses.
Yes, there is a 4D difference between the two eyes.

[wmcdonald]

A 2-Diopter difference may be significant, much less 4. In most cases SV wearers will look down through the optical center. I some cases, patients may not be physically able (neck injuries, etc.) to accomplish that task and will experience diplopia......ergo the need for bi-centric grinding.......slab-off. I hope this is helpful.

[CME4SPECS]

I have a gentleman with similar amount of rx differences. He wears only single vision, I have tried without slab-off and he simply can't wear without slab-off.

[Matthew]

Usually people adapt and drop their head to look through the center rather than the bottom of the lens....

[braheem24]

Use a shallow B,

Force wearer to use more head movement instead of eye movement.

[tmorse]

under what conditions is a slab off required for a patient wearing single vision lenses.
Yes, there is a 4D difference between the two eyes.

If he has a job that requires looking straight ahead, and then looking down, and then straight ahead again, continuously... say watching an assembly line and then writing something down on a clip board.
Yes, I know, not a great example.
Usually he can just drop his head down to write and stays looking the through optical centers. Maybe he has neck issues and too much movement up and down causes pain. SV slab-off is very rare.

But when he hits the big 40 and needs his first bifocals/multifocals, then slab-off would become a real necessity.

[Robert Martellaro]

I had a myopic client last year who was between cataract surgeries, and needed to see the golf ball with his single vision golfing glasses. VI was about 4^ (about -8 and -4). Using a trial frame, I could not eliminate diplopia by positioning the vertical OCs- it was either/or, diplopia far, diplopia near, or diplopia at both angles of gaze. The only solution was a bicentric/slab-off grind, or wait for surgery on the fellow eye. This avid golfer wasn't about to give up his game at the start of the season, so eyeglasses with a slab-off worked as well as expected, and he still had an excuse if the ball went into the trees!