Striker visits youngster in hospital.
Joshua was rushed into the Children's Ward, having lost his sight due to severe swelling around both eyes.
Explaining his son's ordeal a few days after returning home with Joshua, Richard Hearn said: "Joshua is four years old and was admitted to hospital due to a rare disease called hsp and had cellulitis in both eyes causing him to lose his sight.
"Joshua is now out of hospital and is doing well with full vision back.
"He had a very tough time in hospital but was excited when he knew a pro footballer was coming to see him.
"Chris Porter brought Joshua a signed football which he hasn't put down yet.
"It was very kind of him to visit Joshua, we could all see that it gave him a lift in spirits during his stay in hospital."