When the gun sounds, Marla Runyan speeds into the blurry world that is always in front of her. Guided by what she knows and not what she sees, she gets around the track on her confidence and speed, unbothered by the bumping and occasional elbowing from the pack of runners around her.

Marla Runyan is legally blind.

Just 10, 15 feet ahead of her, the fuzzy image of the track fades entirely. She sees a smudged palette of colors and blotted lights -- even her own feet and the colorful jerseys of her competitors don't register clearly. Yet, relying on the dimensions of the track and the rhythm of her pace, Runyan circumnavigates a 1,500-meter course faster than all but a handful of the best runners in the world.

Here at the world track and field championships, Runyan has a chance to prove she is one of the truly elite middle-distance runners. The first step will be Friday's 1,500-meter semifinal, which pits Runyan against a field of 15 runners -- all fully sighted. Having qualified for this event by her performance in the U.S. national championships, Runyan will advance to the final Sunday if she finishes among the top five runners in her heat.

That, however, will be quite a challenge. Though Runyan recently won the gold medal in the 1,500 at the Pan American Games in Winnipeg, her fastest time in the 1,500 this year is 19th best among the runners entered.

"She has met all of my expectations already," said her coach, Mike Manley. "It's my hope, and my belief, that she will be in the finals. And in the finals, anything can happen."

Runyan, 30, is the first legally blind person to compete as an elite athlete in an international competition such as the world championships or the Pan Am Games. She has suffered from a degenerative vision problem since she was about 8. She has 20/400 vision in both eyes. That means if she gets lost while jogging along the banks of the Guadalquivir River in Seville -- as she did this week when she went out by herself -- she has a problem, as she cannot make out the print on any street sign, nor can she see her hotel off in the distance.

It means she can barely see manhole covers along the street, so she is susceptible to spraining her ankle -- as she has done twice -- if the seemingly flat cover is a couple inches above the ground. It means she is in constant danger of crashing into parking meters or speeding bicyclists, which to her seem to pop up out of nowhere.

With all of the dangers and difficulties delivered by daily life and city runs, the place she feels most empowered and secure is speeding around an oval track in a competitive race. For Runyan, the blurred images on a racing oval provide a sustaining and wonderful vision.

"If I was suddenly cured, or my vision was normal, I don't think I would be running any faster," Runyan said this week. "I think life would be easier, but I don't think I would be running any faster. . . . I don't ever feel like I have trouble navigating."

Runyan's retinal degeneration means corrective lenses cannot help her. She has, essentially, holes on both retinas. That's why it's hardest for her to see things directly ahead of her. "It's like a camera," Runyan said, "with bad film."

She owns more than $10,000 in optical equipment that provides assistance with daily tasks. One $3,000 device magnifies anything held under it, such as a needle and a piece of thread. She relies on $2,000 bioptics glasses -- plastic frames rigged with high-powered telescopic lenses -- that allow her see the television or other objects as long as she is sitting still.

An industrial size copy machine sits in the middle of her living room in Eugene, Ore. It's useful for enlarging pieces of mail or magazine articles. Runyan's boyfriend, Matt Lonergan, is a living visual aid. He reads Runyan the newspaper, Track and Field News and restaurant menus.

Along the way, there were many misdiagnoses of her condition -- one doctor announced that Runyan's problem was in her head. Another doctor said she was doomed to go blind.

"It was terrifying," said her father, Gary Runyan, a retired banker, from his home in Camarillo, Calif. "The news we were getting was all bad. They said she may never finish school. When she was going through the early years, there were times she would just go to her room and cry."

When the retinal degeneration worsened, Runyan did all of her reading by holding books close to her face. She leaned over so much her back was always sore, but she was determined to maintain her straight-A average -- and she did. Her mother, Valerie, spent hours making enlarged copies of her daughter's school work. Eventually, Runyan was forced to enter a program for the visually impaired.

Before her vision deteriorated, she participated in gymnastics and soccer. By age 14, she could no longer see the soccer ball, so she turned to track and field. Runyan set the record in the high jump at Camarillo High -- even though she couldn't perceive the bar until she was nearly on top of it. Her father said her achievement in athletics gave her, for the first time, stature among her peers.

"I loved to play sports because I felt I could be more like everybody else," Runyan said. "Actually, I felt I could be even better than everybody else."

At San Diego State, she discovered the helpfulness of audiotapes and "readers" -- volunteers who read aloud her class work. She also decided she wanted to compete in more than just the high jump and sprints. When she announced to her parents that she intended to become a heptathlete, they were horrified. That discipline involves seven events: the 100-meter hurdles, the high jump, the shot put, 200 meters, long jump, javelin throw and the 800 meters.

"The thing that frightened us the most was: How is she ever going to learn to run the hurdles?" her father said. "[San Diego State Coach] Rahn Sheffield trained her to be a hurdler at the expense of black and blue shins."

He added, chuckling: "She was amazed when she found out all the other girls could see the hurdles from the start line."

Gradually mastering the discipline by learning to count the steps between hurdles, Runyan became an excellent heptathlete. In 1996, she set the U.S. record for the fastest 800 meters ever achieved in the seven-event heptathlon (2 minutes 4.70 seconds).

It was during the 1996 Olympic trials that Runyan broke the record, but she finished 10th overall. Because of her performance in the 800 and her disappointing heptathlon result, Runyan decided to concentrate on middle-distance running.

She moved to Eugene, considered by many the running capital of the United States, after the Olympic trials and decided to concentrate on the 1,500. There she met Lonergan, a massage therapist, trainer and competitive marathoner. That's also where she found Manley. Under his tutelage, she finished fourth in 4 minutes 10.02 seconds, then a personal best, at the national championships in June. She has since lowered her best time to 4:06.42, making the U.S. team for the world championships when another runner failed to post a qualifying time.

Manley said he trains Runyan like any other world-class athlete -- with a few minor differences. He announces himself when approaching her so she knows he is there. And he no longer sends her on cross-country runs. After one such trek, she came back well after the other runners, battered by branches and debris that lined the trail.

"She's made a whole lot of progress already," Manley said. "You can't argue with results. She's just starting to scratch the surface, it seems to me. The ability is there."