A New York City man who went blind in 1997 has regained most of his sight, a phenomenon his doctors are struggling to explain.

Kevin Coughlin, 55, of Manhattan, was blinded by optic nerve disease when he was 36, CBS New York reported.

“I literally saw a very thick, impenetrable fog,” Coughlin told 1010 WINS’ John Montone.

Coughlin remained blind until he started seeing shadows in August 2013.

“In August of 2013 I saw a reflection of light on my medicine cabinet mirror after not seeing anything for 16 years,” Coughlin said.

Coughlin then saw the face of Elias, a black lab who was his guide dog at the time.

“I’m seeing more and more, and Elias hasn’t had his harness on for a year and a half,” Coughlin said.

Coughlin said he used to be self-conscious walking his dog through the streets, but now, he walks his dog with confidence.

“When I walked when I was blind I had this very tentative very self conscious gait, and now I have an expansive swagger,” Coughlin said. “Just seeing all the buildings that have been put up in the last 20 years, seeing the restoration of Grand Central Station is incredible.”

Coughlin has regained 70 percent of his vision, and he says it is improving every day. He credits prayer, meditation, and a diet rich with antioxidants, such as spinach, broccoli, and red kidney beans for his regained vision, according to WPIX.

Although he is happy to have regained his sight, he said losing his sight opened his eyes to the suffering of others.

Coughlin’s case is rare, but others have also regained their sight after many years, often due to correctional procedures.

In 2015, a man who was blind for 33 years regained his sight, thanks to a bionic eye, according to ABC News.

A Canadian man born blind could see for the first time at age 68 after being born blind, thanks to a procedure he had because of a fall, the Daily Mail reported.