It's still three episodes away, but February 24 could prove a critical day for MerDer.

In that Thursday's episode, "Not Responsible," she must choose between fertility treatments and her eyesight. This happens after Meredith begins having trouble seeing.

That sounds awfully serious and potentially devastating, or at least heartbreaking, for Mer. How important is her need to be a mother compared to her career as a surgeon?

Meanwhile, Mark wants to make it very clear to Callie and Arizona that he takes his role in their parenting arrangement seriously, and April discovers a different side to Dr. Stark.

Finally, Adele receives treatment for her condition from Richard, Owen and Miranda. Click to enlarge ABC's photo gallery from "Not Responsible" and share your comments:

Steve Marsi is the Managing Editor of TV Fanatic. Follow him on Google+ or email him here.