Unknown foreign object in the eye

Hello everyone, about 3 days ago my 3-year old shih tzu has a small transparent triangular foreign object on his left eye, near the tear duct. It just sticks to the lens and doesn't move. I brought him to the vet and they tried to remove it using a wet cotton ball but to no avail. They couldn't give me an exact answer as to what it is but they said that since there is no swelling or excessive tears, I will have to observe it and flush it with an eye irrigating solution at least twice a day or until it becomes dislodged.

Symptoms include slight sensitivity to bright light, especially in the morning when we wake up; he half closes his eye as if he's sleepy; slight redness on the whites of the eye but when I apply the solution it disappears.

I don't know how and when to remove it. He doesn't even scratch his eye with his paw so that means he's not bothered by it that much.

Anyone has the same experience?

Best regards to you all,
Esthon