How much with-the-rule astigmatism would you intentionally leave in patients under 40 undergoing cataract surgery, considering the expected age-related shift toward against-the-rule astigmatism?  

I think there are a couple ways to look at this, and part of it depends on what your/the patient's goals are (crispest vision at post-op month 1 vs. better uncorrected vision 30 years from now) and what lens you are implanting (monofocal vs multifocal, the latter being less likely to tolerate higher...

IOL selection and expectations are hugely important in this conversation. Will leave less for a multifocal, and more with a standard IOL. A sharpshooter, I might correct all the cyl with a standard IOL, but with the expectation they will need touch-ups. A good place to start is their topo and their...

I agree with Dr. @Christopher. I think leaving a small amount of WTR astigmatism is prudent. A discussion with the patient on what to expect and the possibility of needing a future astigmatism correction as a possibility.