Urgent Care :: Turtle eye infection?

[FTR]

Hello,

So few days ago I noticed my res behaving very strange and different than usual. He became really apathetic, swims weirdly, rubs his right eye and often keeps it closed underwater. But the most concerning thing is that he is unable to get the food, he tries to bite when food is still like 5 centimeters away from him.

I took him to the recommended vet in my area, but she said eye looks normal and it may be just minor infection. He got vitamins shot and prescribed eye drops twice a day (NACLOF).

So my question is, can minor infection have so dramatic impact on turtle behavior? And what about him not being able to even eat by himself, like he became partially blind? Vet said it's becuase they are using their eye sight to hunt. I was told to bring him back to the vet if it gets worse. He is behaving rather normal when on land. I thought it may be something in the water but 40% water change didn't seem to improve anything.

I know I am not in position to question experienced vet, it's just that I am very concerned and I really want this little guy to get better.

edit: adding this

How big is your turtle? 5.5 inch
How long have you had it? 15 years

What is the water temperature? usually 24-25 degrees celsius (75-77 fahrenheit)
Did you use a thermometer? yes
Are you using a water heater? no, turtle tank is standing rather close to radiator so I am afraid heater may be overkill.
How much water is in there? 90% full
Are you using a water conditioner? anti-chlor
Are you using any filtration? yes

What is the basking temperature? it was hard to measure but 34-35 celsius (93-95 fahrenheit)
Is there a basking light? yes
Is there a basking platform that is easy to climb on? yes
What kind is it or what is it made out of? eggcrate (or something very similar)
Is there a UVB light? no

What have you been trying to feed it? pellets, smelts, romaine lettuce, beef heart, regular lettuce, chicory, very rarely sweet tomato or piece of banana
When was the last time your turtle ate? he eats every other day

How big is the tank/pond/enclosure? 40 gallons
Is the tank near a window? yes
Is the tank in a room with a lot of activity? yes

Have you read the Basic Care section? yes
Have you searched the forums for similar situations? yes

Is there any other unusual activity/symptoms? mentioned above

[steve]

Most RES will not try to eat if they cannot see. Is he getting any vitamin a in his diet?

[FTR]

Only from foods he eats that I listed above.

[steve]

Have you noticed any swelling or discoloration? Has the NACLOF been helping?

[FTR]

I didn't and neither did vet. He is still rather passive unless it's feeding time and he still has trouble eating, he noms to the left of food he tries to eat. I was thinking what could possible cause his sickness because in past few months I did some major changes like a new tank, different diet, new tank location (I moved). He was never sick before and he had worse condition than he has now. I think his condition did improve slighly but it's worrying.

Vet told me to get a heater but my room is rather warm and water temperature stays around 77 degrees during a day so I don't really see point of that, unless my termometer shows wrong temperature.

This is the picture of his eye before I started giving him medicine - https://imgur.com/DLxJbTr

He is no longer keeping it closed or half closed so I guess that's improvement.