A teenager was attacked while walking home from his friend’s house on Sunday evening (January 21).
The 18-year-old was assaulted in Bohemia Road between 7.45pm and 8.15pm.
Police said he was badly beaten and struck with a bottle, receiving serious facial injuries including a fractured eye socket and suspected broken nose.
There are believed to be two suspects. and a small quantity of cash was stolen.
Both suspects are described as white men, aged under 40, of muscular build and wearing dark hooded tops, dark tracksuit bottoms, and black scarves over their faces.
The attack happened near Summerfields Leisure Centre.
Detective Constable Mike Pearson said: “This was a particularly vicious and cowardly attack.”
Anyone who witnessed the incident is asked contact Sussex Police online or by calling 101, quoting serial 1128 of 21/01.