Hi there, you are through to Dr. Jake Im a UK based vet. im sorry to hear of your concerns with your turtle, Fiddy.
Ocular problems are common in turtles. they can often get eye infections which results in puffy swollen eyes , where they eyelids cant open or have a film across them, similar to the signs you are describing. This can often be due to an underlying cause such as vitamin A deficiency in turtles- it is important that they receive adequate levels of vitamin A in their diet through a fully balanced diet consisting of gut loaded and supplemented live food where multivitamins are used combined with fully formulated turtle pellets and fresh veg
Lighting for turtles should be correct, incorrect lighting can also damage eyes or cause problems. they should have an area to get out of the water and dry off. a spot bulb used as a basking spot should be provided along side UV light to prevent metabolic bone disease. its important that these are positioned correctly, the correct strength of bulb is used and not angled as this can potentially affect the eyes.
Poor water quality can also play a factor in this also and can increase the risk of infection. adding new plants can result in pH changes and alterations in nitrate , ammonia and nitrite levels. i would recommend getting a water quality testing kit from your local reptile or fish shop to check the water quality is correct which can be altered if needed. Turtles are generally messy animals and filtration and water changes need to be frequent also to ensure water quality is adequate.
the lesions you describe on the feet could also be related to water quality or infection - bacterial and fungal infections on the skin are also common.
I would recommend an appointment with your local reptile vet for the eyes and skin to be examined. they may wish to take small samples from the feet to look at under the microscope to see what sort of infection is present, if any, to help determine what type of treatment is needed. They can also assess the eyes and prescribe appropriate medications which are usually eye drop and oral anti biotics.
i hope all this information helps