The 31-year-old man was seriously injured when an egg was thrown at his face at about 11.15pm last Friday night (Jan 10) in Newton Lane, Wigston.
Shortly afterwards eggs were hurled from a car in Welland Park Road, Market Harborough.
The two incidents are being linked.
The victim was riding into Wigston when an egg was thrown from a car travelling in the opposite direction.
He had a crash helmet on but his visor was up and the missile hit him in the face.
The man from Leicester had emergency surgery at hospital but the sight in his right eye could not be saved.
Police today said the car believed to be involved in the incident is a red Seat Leon 69-plate.
The vehicle has been recovered.
A 17-year-old Leicestershire youth was arrested by motorway patrol officers on Saturday night as police hunted the offenders.
He has now been freed on police bail pending further enquiries after being questioned.
Det Con Jack Thomas, of Leicestershire CID, said: “Our investigations remain very much ongoing and we have now released the further details in relation to the car believed to be involved.
“Please think back to late Friday evening.
“Did you see a red Seat Leon car in the area of Wigston or Market Harborough driving in a manner which caused you concern?
“Did you see eggs being thrown?
“Have you seen or heard any information since which may help our enquiries?”
He added: “I appreciate it is not something you would necessarily think to report to the police initially.
“But this is a very serious incident which has led to the victim losing his sight in one eye. “This is an incident which has seriously affected the victim’s life and the lives of his family.
“My thanks do go to those people who have come forward with information so far in relation to the incident.
“We are looking into this information received as part of our ongoing enquiries.”
Anyone with any information should contact police on 101 quoting crime number 20*19279.