A church dedicated to Kosmos and Damian was built during the reign of Theodosios II in the suburbs of Constantinople; numerous miracles were ascribed to this shrine. An attached monastery is first attested in the 6th century. Because of its vulnerable location outside the walls, in present-day Eyup, the church was destroyed in the Avar attack of 626. It was, however, restored by the 8th C. In the 11th century Michael IV the Paphlagonian was responsible for major improvements at the monastery; he provided bathhouses, lawns, and fountains, in addition to commissioning the rebuilding of the church and its decoration with mosaics and marble revetment. It was to this monastery that, suffering from terminal illness, he retired in 1041; he received the monastic habit on the day of his death. He was buried in the church he had restored. The monastery of Kosmas and Damianos is mentioned frequently in sources of the Palaiologan period and apparently survived until 1453. It should be distinguished from the contemporary nunnery dedicated to the same saints, which was restored in the late 13th century. by the Dowager Empress Theodora, widow of Michael VIII.
Oxford Dictionary of Byzantium edited by Alexander Kazhdan