Using ithmid before sleep is from the sunnah of the Prophet ﷺ.
Abdullah ibn ‘Abbas (Allah be pleased with him) reports that the Messenger of Allah (Allah bless him and give him peace) said,
“The best antimony/collyrium is ithmid, (applied) before sleeping, it helps the (eyelashes) to grow and sharpens the eyesight.”
[Ibn Majah, Musnad Ahmad, Musannaf Ibn Abi Shaybah, Sunan Abi Dawud]
Some narrations mention to apply ithmid three times in each eye, and some only twice in the left eye.
