Volleyball star Kim Glass -- who won a silver medal at the 2008 Beijing Olympics -- says she was attacked by a homeless man in Los Angeles this weekend ... and nearly lost her eye in the incident.

Glass said it all happened on Saturday ... after she was leaving lunch with a friend at a restaurant in Downtown L.A.

In a series of videos posted to her social media page, Glass said after she had exited the eatery, she noticed a man in the street with something in his hand.

"He just like looked at me with some pretty hateful eyes," Glass said. "And, as I turned to go tell my friend, 'I think something's, like, wrong with him and I think he's going to hit a car,' before I knew it, a big metal bolt, like pipe, hit me right here."

"It happened so fast."

The 37-year-old said the man threw the object at her from several feet away ... and it slammed right into her eye socket and the bridge of her nose -- 'causing serious damage.

In her videos, taken a day after the attack, you can see her eye was nearly swollen shut, and her face was still bloodied. She said in the clips she was diagnosed with multiple facial fractures and needed stitches to close wounds.

Somehow, Glass said doctors don't expect her vision to be permanently affected by the incident. She added she was grateful for all the support she's received from friends and family since the incident, and happy things didn't turn out worse.

"Just be safe out there," she said in her videos ... "There's a lot of mentally ill people on these streets right now and you shouldn't have to be fearful when you walk but it's true. And, so, you guys just be safe."

As for the man who she accused of throwing the object, she said bystanders held him down until police arrived. No word if the man was ultimately arrested.

Glass -- a 6-foot-3 outside hitter -- played for the U.S. Women's National Team for years following a stellar career at the Univ. Of Arizona ... and also modeled in her time off the court, appearing in the 2011 Sports Illustrated Swimsuit Issue.