وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا
«أَنَّ اَلنَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ اِكْتَحَلَ فِي رَمَضَانَ، وَهُوَ صَائِمٌ»
Aishah (RAA) narrated, The Messenger of Allah (sallallahu alayhi wa sallam) applied kohl to his eyes while he was fasting. Related by Ibn Majah with a weak chain of narrators. According to At-Tirmidhi, nothing authentic has been related from the Prophet (sallallahu alayhi wa sallam) concerning this issue, i.e. applying kohl, eye drops etc. to the eye while fasting.
Bulugh al-Maram 776, Book 5, Fasting, Hadith 19. 1 min read