In the wake of recent concerns about the effects of prolonged weightlessness on eyesight, space station astronauts now are carrying out regular tests and eye exams to collect more data on how their vision might be affected, the lab's commander said Thursday.

Japanese astronaut Satoshi Furukawa holds an eye chart in the Destiny laboratory of the International Space Station. Credit: NASA

"Periodically, we do different tests and this week is one of those weeks where we do the vision tests," Expedition 29 commander Mike Fossum told CBS News. "First is the visual acuity test, which everybody does when you go to the doctor's office. Yesterday, we performed ultasounds of our eyes, where we measured the details of the eyeball to see if there's any physical changes, including the optic nerve on the back of the eyeball.

"This is new stuff, they're keeping a close eye on things like that. We'll be taking images of our retina later today. Two days ago, we took tonometry measurements, which (characterize) the intraocular pressure. So far, we're in great shape and ready to stay up here as long as we need to."

A recent report by the National Academy of Sciences said seven of 15 station crew members who were tested had experienced various levels of papilledema, or blurry vision, caused by intracranial pressure and swelling of the optical disk, "with some lingering substantial effects on vision." It has been reported that about 35 percent of space station astronauts have experienced blurry vision of some sort.

But Expedition 29 flight engineer Satoshi Furukawa, a Japanese physician-astronaut, said the current crew has not had any problems.

"We periodically inspect each other and no problem at all," he said.

The International Space Station is currently staffed by a crew of three -- Fossum, Furukawa and cosmonaut Sergey Volkov. Expedition 28 crew members Ronald Garan, Andrey Borisenko and Alexander Samokutyaev returned to Earth last month, but launch of three replacements was delayed from Sept. 22 to Nov. 14 in the wake of a Soyuz launch failure August 24 that destroyed an unmanned Progress supply ship.

Russian engineers believe the third stage malfunction was caused by contamination in a fuel line and Fossum said Thursday the program appears to be back on track. Another unmanned Progress launch is targeted for Oct. 30 while the Soyuz TMA-22 crew -- Anton Shkaplerov, Anatoly Ivanishin and NASA flight engineer Dan Burbank -- is gearing up for launch to the station at 11:14 p.m. EST (GMT-5) on Nov. 13.

"I talked to dan Burbank yesterday," Fossum said. "All the word we're getting is things are on track," Fossum said. "It seems to be an unexplained anomaly in the fuel system, so they've added in more tear-downs, re-inspections as they get it certified and prepare to go do a test launch leading up to flight. So everything seems like it's on track. There are some very big events coming up that will really determine how close to the current schedule we stick. But everything sounds good and everyone's moving forward."

Fossum and his two Soyuz TMA-02M crewmates are scheduled to return to Earth Nov. 22. If the current schedule holds up, the outgoing crew will only have one week to brief the incoming TMA-22 crew members on the intricacies of space station operations. But Fossum said he does not anticipate any problems.

"The advantage that we've had of overlapping crews is a really solid handover," he said. "Normally when ... the senior crew leaves, the other guys are up to full speed and ready to take over, just like we were when the (Expedition) 28 guys left. And so, it'll hurt efficiency a little bit as they're not quite as quick accomplishing things, because they're working through it more and have to ask more questions."

As for operating the station with a reduced crew of three for an extended period in the wake of the Progress failure, Fossum said "so far, so good."

"We're going full speed ahead up here, Satoshi and I are holding down the fort on the (U.S.) side of the station, we're meeting our goals, actually exceeding our goals for science right now," he said. "There's very little impact to us at this point. We have all the supplies we need. We're working hard, but we're getting the job done."