Answered by Shaykh Yusuf Weltch
Is Eye rust impure?
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