A young man’s dream career has been put on hold after being blinded by a thug in a pub assault.

The victim, 19, was enjoying a night out with friends when another patron offered him drugs at the Royal Melbourne Hotel on the morning of February 17.

The teenager said no and continued to talk with the stranger, who then followed him to the bathroom.

The offender fled the scene on foot to a nearby train station after the attack. (Victoria Police)

As he attempted to leave his cubicle, the other male stopped him and retrieved a metal spike.

He demanded cash and threatened the 19-year-old, before stealing his sunglasses.

The thug then followed the victim out of the bathroom and punched him in the face.

“I went dizzy, I felt pain and couldn’t see anything immediately,” the victim said today.

The offender was wearing this muscle top at the time of the assault on February 17. (Victoria Police)

He suffered instant blindness in the right eye and other serious facial injuries as a result of the blow.

Police have called the actions of the attacker “cowardly”.

“This has changed the rest of (the victim's) future. It’s possible he will be blind in the right eye for the rest of his life,” Detective Senior Constable Jodie Hill said.

The victim said he was just about to start a new job as an air conditioning installer, a plan that has now indefinitely been put on hold.

The offender, believed to be aged in his 20s, fled the scene out the back of the venue to Southern Cross train station on Spencer Street.

Detectives have described the thug as being about 177cm tall, with a medium to solid build and dark curly hair.

He was wearing black baseball cap, a white ‘Nena & Pasadena’ muscle top and blue jeans with maroon NMD runners at the time of the incident, which unfolded about 6am.

Investigations are ongoing.