When do you use the Xpan diopters?

[parasko]

Hi all,

Any ideas when the optional Xpan diopters are used?

I wear glasses so if I purchased one of the optional diopters based on my glasses specifications, do I use the diopter whilst I'm wearing glasses or is the diopter a substitute for wearing glasses?

My second query is that I cannot find any information regarding which particular diopter is compatible with my glass specifications for the 30mm lens.

Is there a chart on the internet somewhere which matches up glasses specs range with the diopters for the 30mm lens?

Lastly, has anyone used these diopters and are they worth purchasing?

Any advice appreciated. Thanks.