Prince Charles was so moved by a late-night visit to London slum areas last November that he has made two of his London houses available as overnight shelters for the homeless, an aide announced Thursday.

The aide, Harold Haywood, told reporters that after the visit Charles told him, "We must do something to help." The Daily Telegraph reported that the houses are in South London.

Buckingham Palace said Thursday it had assured Prime Minister Margaret Thatcher's office that Charles was not criticizing her in remarks on urban decay attributed to him by a royal adviser this week. As the heir to a constitutional monarchy, Charles is supposed to avoid taking sides on political issues. Ortega's Sightly Expense

Nicaraguan President Daniel Ortega and first lady Rosario Murillo, in New York for the U.N. anniversary session, bought $3,500 worth of fashion eyeglasses from an East Side optician this week and covered the splurge with a Diners Club card, shop manager Jeff Kirsch told The New York Times.

"They were here an hour. He was easygoing, he took whatever his wife said. She was very picky," said Kirsch. Murillo ordered three Gucci frames for herself and three Fioruccis for her daughter. Ortega bought six Silhouette frames with lenses of polycarbonate, the sturdy plastic used for bulletproof shields in taxicabs. His eyeglasses were $300 each. Gucci frames start at about $180 each, said Kirsch, and Fioruccis run about $50 less.

Yesterday, after a speech to a crowd of more than 1,000 at the New York Society for Ethical Culture, Ortega ignored a question about the purchase. However, his information minister, Manuel Espinosa, later denied the reports that Ortega paid with Diners Club or that he spent $3,500. End Notes

Jihan Sadat, widow of Egyptian president Anwar Sadat, has donated three items to an auction scheduled today at Cave Spring Elementary School in Roanoke. PTA member Shirley Black wrote to Sadat asking for a contribution to the auction, Principal Thad James said. Sadat, who is a visiting scholar at Radford College, sent the school a brass plate from Egypt, an Egyptian painting on papyrus and a photograph of herself with her late husband. The proceeds will be used to buy extra school supplies . . .

S.I. Newhouse Jr., chairman of Advance Publications Inc., has been named "publisher of the year" by the Magazine Publishers Association. Newhouse will receive the Henry Johnson Fisher award Jan. 15 at a formal dinner in New York. Advance Publications Inc. includes the Conde Nast Publications and The New Yorker magazine . . .

The 75-year-old fraternity house that held the title role in the 1977 movie "Animal House" faces demolition after the Eugene, Ore., Historic Review Board rejected a move to save it. A medical clinic is planned for the site. No decision has been made on when demolition will begin, according to businessman Harry Rubenstein and builder Ron Braatz, two principals in the project . . .

Cathleen Crowell Webb has given some of the royalties of a book she wrote to Gary Dotson, the man she says she falsely accused of rape six years ago, her lawyer said. The undisclosed sum reportedly is 75 percent of advance royalties for the book, titled "Forgive Me." In exchange, Dotson was required to sign a release promising not to sue Webb, his attorney said . . .

Former senators Eugene McCarthy and Walter Mondale, both Minnesotans, cohosted a fundraiser Thursday night for state-mate Rep. Gerry Sikorski. Guests dined on such native Minnesotan delicacies as moose meatballs, buffalo meat and antelope stroganoff, prepared by residents of the Leech Lake Chippewa Reservation.