One thing I would suggest is Tortoise Eye Drops. They can be found at the pet shop. Ours had eye infections a couple of times. We put them in once a day and after about a week/week and a half, she was much better. Also give him some nice luke warm baths to kind of rinse out any possible dirt or crud. I would be careful on the lettuce. We only do hay, grass, dandelions, kale (not very often), and cactus as a special treat. Some lettuces will not have the types of nutrients they need to grow right.
Is she eating? About a year ago, I had a family member who took in a wild box turtle, and she quickly got swollen eyes. She also stopped eating, and was sleeping a lot. Does she/he live inside? This box turtle did not have proper heating/UVB. The person who had the box turtle, ended up letting her go, and I believe because, I think he found her a while later. Maybe if you give him/her soaks and keep her outside with natural heating and UVB she/he would recover. I hope this helps!
