Al-Amash said: I did not see any of our companions who abominated the use of collyrium by a man who fasting. Ibrahim would permit the man who was fasting to apply collyrium with aloes.
Explanation & Benefits
Shaykh Umar Farooq Saeedi
Benefits and Issues:
It is permissible to apply kohl to the eye or to instill medicine into the eye while in the state of fasting.
Source: Sunan Abu Dawood – Commentary by Shaykh Umar Farooq Saeedi, Page: 2379