Arsenal goalkeeper Petr Cech says he would feel more confident playing without his protective helmet but accepts it is in his best interests.
Cech, 33, has worn a scrum cap since he suffered a head injury in a clash with Reading's Stephen Hunt while playing for Chelsea in 2006, and he said it has hindered his performance.
The Czech Republic international spent three months on the sidelines with a fractured skull and said that in his return match -- a 2-0 defeat at Liverpool in January 2007 -- he lost his spatial awareness and that it affected his hearing.
Even if he now has grown accustomed to it, he believes it has a negative impact on his ability to perform.
"Whether you like it or not, the helmet affects your surroundings. You have your ears covered and it makes hearing worse.
"But the doctor has forbidden me to take off the helmet. If I did, I would not get insurance."
Cech said he has suffered concussion while wearing the helmet -- notably against Fulham in 2011 -- and added: "I don't want to think what would have happened to me without it."
Meanwhile, Cech said he is shocked by Chelsea's fall from grace this season.
Cech ended an 11-year spell at Stamford Bridge when he joined Arsenal in the summer, and has seen the side that won last season's title claim just 11 points from 12 Premier League games so far.
"It makes me surprised," Cech said. "It's a team that six months ago won the league.
"Players stayed there, the coach added more to his liking. It is very hard to believe that the club is in such a state.
"I was surprised to see their suffering at the beginning of the league, but I was even more taken aback by the fact that the crisis still continues."