After studying medicine at
King's College, London, Henry Cayley joined the Indian Medical Service in 1857 as an Assistant Surgeon. From 1858 to 1864 he was in charge of the 2nd Sikh Police Corps at
Gorakhpur near the border with
Nepal. From 1864 to 1866 he was
Joint Civil Surgeon at
Simla, the summer capital of British India. After holding the post of Civil Surgeon at
Burdwan and then
Howrah, he was appointed joint commissioner at
Ladakh in 1867. The native government of Ladakh had accepted an army officer in the post only on condition that a medical officer was selected. Henry Cayley's duties there were both political and medical. In December 1867 a newspaper commented that "the reported assassination of Assistant-Surgeon H Cayley, the British representative at Ladak, was without foundation; and some very interesting notes by him respecting that remote region have just been published." In 1870 he was a member of a British mission to
Yarkand, where Ladakh had trading links. His appointment ended in 1871, when he went on leave in England. There he extended his medical knowledge, particularly though studies in ophthalmology at
Moorfields Eye Hospital. Shortly after his return to India, he was appointed Superintendent of the Eye Infirmary at Calcutta and Professor of Ophthalmic Surgery in
Calcutta Medical College. ==England and South Africa==