General manager Ruben Amaro Jr. said Wells will be re-examined Wednesday at Wills Eye Institute. Wells did not travel with the team.
Sandberg said Wells underwent LASIK surgery in November before trying contact lenses and most recently prescription goggles, but his eyesight never improved enough for him to feel comfortable.
"It finally got to the point where he didn't feel right about that," Sandberg said. "He mentioned production and the betterment of the team and for himself to go ahead and get that looked at and see if he can get that fixed."
Wells also told Sandberg he was experiencing dry eye in the field. So if he was in the outfield or at the plate and didn't blink at just the right time to focus clearly, the ball would be blurry as it neared him.
The Phillies are the third team Wells has played with this season after they claimed him off waivers from the White Sox on Aug. 8, but the first he's told about his vision problems.
"This is the first time he went to a club and said, 'I've had this issue.' He didn't want to use it as an excuse," Amaro said. "I think it got to the point where the other night, he actually started to get more fearful."
Sandberg called it a scary situation, and Amaro said the team wants Wells to get checked out not just for his safety, but for his short- and long-term well-being.
In 11 games with Philadelphia, Wells was only 1-for-23 at the plate. Overall, Wells, who also spent time with the Athletics, is hitting .128 this season.
"You don't know whether that was because he was just struggling or because he was just not seeing the ball well," Amaro said. "Obviously he was having this issue, so it could've been part of it."
Chris Iseman is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.