Gas permeable lenses and cataract surgery

When planning cataract surgery (to include a toric lense) in the patient who wears RGP lenses, is there "Gold Standard" for the time-frame the lenses should be taken out before surgery? Are there circumstances in which they may be left in place when measurements are done?  

[John C Hagan III, MD, FACS, FAAO]

Never left in place. Most often go 3-6 weeks with corneal readings the same taken a week apart.

JCH MD