Posted By Bob Pedley
Sarah,

The only danger I am aware of is if you change from one type of lens to another when going from normal specs to safety specs.
I believe you should look at the prescription the wearer normally has and ensure they get like for like. The periferal vision will be the same regardless of the type of lens in a safety spec as you won't be looking through it.
This applies to all wearers not just plant drivers, as the change can be more drastic when looking down whilst decending stairs etc.

Regards

Bob

Posted By Sarah J Shaw
To clarify where my query comes from. We have an occupational health dept on site and they have stated that FLT drivers should not wear varifocals when driving FLTS as they give a distortion to the periferal vision.

If you look at bifocal lenses as compared to varifocals they work differently ie when you look through the periferal area you are not using the close too parts of the lense, only the longer distance because you don't need it. With varifocals however the altered area of vision goes all the way across the lense hence the impaired vision when driving. Think about when you look over your shoulder when driving a car, you don't use the centre of the lense just the side.

I was wondering if this was something anyone else had come across, or knew of a formal reference to it.

I agree that changing someones lense type does adversely affect them as there is a technique to wearing these modified lenses. However if there is a risk either way I wanted to explore this further.

Sarah