The London Eye shut on Wednesday night after a piece of metal fell off and hit a canopy, showering people with glass.
The London Eye is one of the city's most popular attractions
The popular tourist attraction was able to reopen after engineers worked through the night to make repairs and find out what happened.
Teenagers who were boarding the Eye were hit with some glass, but managers said no-one was injured.
A metal pin cover from the wheel's hub came loose and fell about 70m onto protective safety glass.
Pupils on a summer taster course at St George's medical school in Tooting were on a trip out when the accident happened.
Student mentor Douglas Hing said: "I could see...a shattered glass panel that acted as a roof for the walkway where people stood, right where we were about ten seconds before."
'No one in danger'
Managers say no-one was in any danger and they are confident it was a one-off occurence.
London Eye spokesman David Sharpe said: "I'm very pleased to say the toughened glass worked very well.
"Having studied the CCTV footage, we did a very good job in evacuating the area because, at the time, we weren't sure what had happened."
The Eye opened on Thursday morning, after talks with the Health and Safety Executive.
"Having had engineers working on it all night, we will make sure it doesn't happen again," said Mr Sharpe.