In cases where placing a IOL in the bag/sulcus is not possible, how do you decide between leaving a patient aphakic for a scleral fixated IOL (assuming this can't be done immediately) vs. placing an ACIOL?  

In 2 situations, I would leave a patient aphakic even without an IOL: highly myopic patients where the actual IOL power is minimal +\- 3 D, in that case, glasses can correct residual refraction, supposing that the patient does not develop anisometropia monocular patients with up to 5 D residual ...

In general, I try to avoid placing an ACIOL unless the patient is older and I think going through another surgery may be more risk than reward. Well-placed ACIOLs can do well for decades, but I still prefer scleral fixation when possible.