German GP: Brake fragment caused Button's eye problem

Button has since been given the all clear to continue for the remainder of the last grand prix before Formula 1's summer break.

The Briton had only completed 16 laps in the second practice session at Hockenheim when he was sidelined by an irritation in his left eye that prompted a visit to the medical centre and then a hospital in Mannheim.

"Everything was OK, I just had something in my eye, some carbon or something I had to have taken out," said Button upon his return.

"I've had it before, a bit of carbon from the brakes. It wasn't just dust in my eye, it was a bit more severe than that.

"They didn't have any systems to check it here [at Hockenheim], so I had proper checks at a hospital, and they found something, washed it out, and all good.

"It was very painful, and that's why I stopped early.

"To be fair, the team said they needed six laps of data on the super-softs, and we were OK because I'd actually done six laps before I stopped."

Button ended the session eighth quickest, 1.473 seconds adrift of pacesetter in Mercedes' Nico Rosberg, and 0.138s ahead of team-mate Fernando Alonso who was 10th.

He was generally satisfied, despite missing out on track time.

"The session was alright, apart from my eye," added Button.

"The feeling with the car was not too bad. I didn't get a good lap on low fuel because we had traffic in the last sector, but still, we were eighth.

"There's always time to find and things to improve, but our aim now has to be the fourth best team tomorrow."