Reference: Fataawa Ramadhaan – Volume 2, Page 513, Fatwa No.476
ad-Durar as-Sunniyyah fil-Ajwibah an-Najdiyyah – Volume 5, Page 351
Question: If a person puts some [medicinal] eye drops in his eye[s] during the night and then found it’s taste in his throat the [following] day, [does this affect his fast]?
Response: If he put the [medicinal] eye drops in his eyes during the night and found it’s taste in his throat during the [following] day, then I anticipate this will not affect [the correctness of his fast, in shaa.-Allaah].