Hadith #726 (Jami' al-Tirmidhi)
Book: The Book on Fasting
Narrator(s): al-Hasan bin Atyh bin Njyh الحسن بن عطية بن نجيح, Anas ibn Malik

a man came to the Prophet and said: “My eyes are bothering me, can I use Kuhl while I am fasting?” He said: “Yes.”

Source: https://parallelquran.com/hadith/jami-al-tirmidhi-726/