All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
If there is a necessity to apply artificial eyelashes due to damage of one's natural eyelashes as a consequent of a disease, burning, or any other accident – we ask Allaah to protect all Muslims from afflictions – and it resulted in changing and disfiguring the face, it is permissible to do so according to necessity. In fact, necessity must only be answered proportionately, so it is impermissible to use more than needed.
If these artificial eyelashes are used for beautification purposes, two sorts of evil are involved: first: it is a change of the creation of Allaah, second: it is included in the general prohibition reported by the Prophet, sallallaahu ‘alayhi wa sallam, in the Hadeeth where he said: "I curse women who fix hair extensions and those who have hair extensions done." [Muslim]
The woman who fixes hair extension is the one who lengthens her hair with other hair.
Allaah Knows best.