 He held this role for 20 years, eventually rising to the post of chief of the photo unit prior to his retirement from the UN in 1998.In 2008, he co-authored a book, "The Vale of Kashmir", about the people and landscape of Kashmir.In 2009, "Outdoor Photographer" magazine published a feature story about the book and Isaac, noting, "The book was a daunting undertaking, especially for a retired photographer."