Answered by Shaykh Yusuf Weltch
Question
Is Eye rust impure?
Answer
In the Name of Allah, the Most Merciful and Compassionate
No. Eye crust is not impure. It may be considered a dirty substance, however, impurity (najasa) is a legal term for a very select number of things. Eye crust is not of those things. [Maydani, al-Lubab fi Sharh al-Kitab]
Hope this helps
Allah knows best
[Shaykh] Yusuf Weltch
Checked and Approved by Shaykh Faraz Rabbani