what could cause a swimming feeling

Patient came in with a -8.00 and -5.00 and ordered glasses. When picking up, she immedidately said she can see clearly but that there is a swimming feeling which she was even afraid to drive home with them. She called later as well and said it hadn't improved at all. I was able to call the place where she got her previous glasses. PD's: same numbers, Index Ours: 1.67 Theirs: 1.66, OC HT: I took one, Theirs: none taken. BC: Theirs: 1.75 R 2.75 L Ours 2.75 R: 3.75 L She further reported that she feels like she has to place her eyes at the very top to get any relief. Is there any chance that she could have gotten used to the OC height being too low and/or the base curves being different. Oh, and the prescription was only changed .25 in the distance stronger. Help.