Ad Dajjaal – this is taken from dajala dajlan (to deceive), so therefore he tells lies and he lies in wait because he claims ruboobeyah (lordship) – and this is from the greatest of lies. And he is present (in this time).
As for his being one eyed, then it is taken as a reality because the basic principle regarding speech is that it is taken as a reality.
The emergence of the maseeh ud dajjaal is from those matters which are established from the Prophet sal Allaahu alaiyhi wa sallam in the authentic Ahadeeth which are mutawaatir (which have multiple narrators at each step of the chain of narration).
And with Allaah is the tawfeeq. And may peace and blessings be upon our Prophet, Muhammad and upon his family and Companions.