Japan's Emperor Emeritus Akihito, the father of the current Emperor, has turned 89 years old.

He will mark the occasion on Friday with a simple ceremony at his residence in Tokyo. Emperor Naruhito and Empress Masako will attend.

The Emperor Emeritus was diagnosed with heart failure in July, but officials say his condition appears to be improving with treatment.

He also underwent cataract and glaucoma surgery in September and the prognosis is reportedly good.

Officials from the Imperial Household Agency and sources say the Emperor Emeritus takes walks around his garden every morning and evening, and waves back when he sees people in nearby buildings waving to him.

They say he has resumed playing the cello and takes lessons twice a month. His wife also attends from time to time to listen to his music.

The Emperor Emeritus also visits the Biological Laboratory in the Imperial Palace grounds twice a week to continue his research on gobioid fishes. He has studied the species for many years.

The officials say the couple read aloud every day essays and textbooks they used as elementary school students.

The Emperor Emeritus and Empress Emerita moved in April to the Akasaka Estate in Tokyo's Minato Ward, where the couple lived for more than 30 years after getting married.