Must sleep only on back for 3 days after corneal transplant!

I am on the waiting list for a corneal transplant. Apparently after the surgery I must stay in bed on my back for 3 days. I may sit up to use the bathroom or eat prepared meals. I have had back surgery (L4-5) and have arthritis. I have a special knee pillow to use. Any other thoughts about how to be comfortable for these 3 post-surgery days?