Abiathar Crescas was a 15th-century Jewish physician

Physician

A physician is a health care provider who practices the profession of medicine, which is concerned with promoting, maintaining or restoring human health through the study, diagnosis, and treatment of disease, injury and other physical and mental impairments...

 and astrologer

Astrologer

An astrologer practices one or more forms of astrology. Typically an astrologer draws a horoscope for the time of an event, such as a person's birth, and interprets celestial points and their placements at the time of the event to better understand someone, determine the auspiciousness of an...

 in the kingdom of Aragon

Aragon

Aragon is a modern autonomous community in Spain, coextensive with the medieval Kingdom of Aragon. Located in northeastern Spain, the Aragonese autonomous community comprises three provinces : Huesca, Zaragoza, and Teruel. Its capital is Zaragoza...

 (now part of Spain

Spain

Spain , officially the Kingdom of Spain languages]] under the European Charter for Regional or Minority Languages. In each of these, Spain's official name is as follows:;;;;;;), is a country and member state of the European Union located in southwestern Europe on the Iberian Peninsula...

). He was head astrologer to King John

John II of Aragon

John II the Faithless, also known as the Great was the King of Aragon from 1458 until 1479, and jure uxoris King of Navarre from 1425 until his death. He was the son of Ferdinand I and his wife Eleanor of Alburquerque...

 of Aragon, father of King Ferdinand

Ferdinand II of Aragon

Ferdinand the Catholic was King of Aragon , Sicily , Naples , Valencia, Sardinia, and Navarre, Count of Barcelona, jure uxoris King of Castile and then regent of that country also from 1508 to his death, in the name of...

 of Aragon

Aragon

Aragon is a modern autonomous community in Spain, coextensive with the medieval Kingdom of Aragon. Located in northeastern Spain, the Aragonese autonomous community comprises three provinces : Huesca, Zaragoza, and Teruel. Its capital is Zaragoza...

.

Crescas was a very prominent Jewish figure in Aragon. He could remove cataracts by a surgical procedure known as couching

Cataract surgery

Cataract surgery is the removal of the natural lens of the eye that has developed an opacification, which is referred to as a cataract. Metabolic changes of the crystalline lens fibers over time lead to the development of the cataract and loss of transparency, causing impairment or loss of vision...

, and was most famous for restoring the eyesight of King John in two simple operations.