LOS ANGELES (AP) -- Anderson Cooper says a reporting assignment turned into a temporary blindness scare.

On his talk show Tuesday, Cooper said he was in Portugal last week working on a story for "60 Minutes" and spent two hours on the water. The newsman says that later, he developed a burning sensation in his eyes and lost sight for 36 hours.

Showing a photo he took of himself with an eye patch, Cooper joked it would be his new online dating picture.

On a more serious note, Cooper said he wanted to warn viewers about the risk.

Dr. Nancy Snyderman, chief medical correspondent for NBC News, explained to Cooper he had suffered a retina burn. Snyderman cautioned that "everybody needs sunglasses," adding that protection from the sun can prevent cataracts later in life.