Box turtles are lovely pets to have as they have great personalities and are intelligent turtles. Caring for them is not always easy though and its likely that you may find yourself in a situation where your box turtle is in need of extra care. For example if they have a turtle eye infection.
If you think your box turtle has an eye infection the first thing you should do is look for any other accommodating problems such as your turtle having a runny nose, breathing with their mouth open and wheezing or gasping while taking in breathes of air. If you have spotted any or all of these symptoms then it's very likely that your box turtle has a respiratory infection and will need to see the vet as soon as possible.
A box turtle with swollen eyes may be a case of your turtle being allergic to the substrate in their enclosure. Some turtles are allergic to earthly substrates and will have swelling around the eyes as a result of their allergy towards this sort of bedding. If your using earth or soil based bedding then try replacing the bedding with another and monitoring your turtle for a week or so to see if the swelling goes down. If the swelling still persists then you will know that your turtle does not have allergy problems and it could be because they are lacking vitamin A in their diet.
Swelling eyes can be caused by a lack of vitamin A and by simply giving your box turtle more foods rich in vitamin A the swelling can go down considerably. Foods such as Collard greens, carrots, kale and parsley all contain a good amount of vitamin A and can be added to each meal to help fight against this problem.
If nothing changes and the problems your box turtle is having remains then its time to see a vet. A vitamin injection might be necessary to help restore your turtles health and fix their turtle eye infection altogether.