Ottoman Empire
In the Ottoman Empire, eunuchs were typically slaves imported from outside their domains. A fair proportion of male slaves were imported as eunuchs. The Ottoman court harem—within the Topkapı Palace (1465–1853) and later the Dolmabahçe Palace (1853–1909) in Istanbul—was under the administration of the eunuchs. These were of two categories: black eunuchs and white eunuchs. Black eunuchs were African slaves who served the concubines and officials in the Harem together with chamber maidens of low rank. The white eunuchs were European slaves from the Balkans or the Caucasus, either purchased in the slave markets or taken as boys from Christian families in the Balkans who were unable to pay the Jizya tax. They served the recruits at the Palace School and were from 1582 prohibited from entering the Harem. An important figure in the Ottoman court was the Chief Black Eunuch (Kızlar Ağası or Dar al-Saada Ağası). In control of both the Harem and a net of spies among the black eunuchs, the Chief Eunuch was involved in almost every palace intrigue and thereby could gain power over either the sultan or one of his viziers, ministers, or other court officials. One of the most powerful Chief Eunuchs was Beshir Agha in the 1730s, who played a crucial role in establishing the Ottoman version of Hanafi Islam throughout the Empire by founding libraries and schools.
Sixth nerve palsy, or abducens nerve palsy, is a disorder associated with dysfunction of cranial nerve VI (the abducens nerve), which is responsible for causing contraction of the lateral rectus muscle to abduct (i.e., turn out) the eye. The inability of an eye to turn outward, results in a convergent strabismus or esotropia of which the primary symptom is diplopia (commonly known as double vision) in which the two images appear side-by-side. Thus, the diplopia is horizontal and worse in the  distance. Diplopia is also increased on looking to the affected side and is partly caused by overaction of the medial rectus on the unaffected side as it tries to provide the extra innervation to the affected lateral rectus. These two muscles are synergists or "yoke muscles" as both attempt to move the eye over to the left or right. The condition is commonly unilateral but can also occur bilaterally.The unilateral abducens nerve palsy is the most common of the isolated ocular motor nerve palsies. Signs and symptoms
The nerve dysfunction induces esotropia, a convergent squint on distance fixation. On near fixation the affected individual may have only a latent deviation and be able to maintain binocularity or have an esotropia of a smaller size. Patients sometimes adopt a face turned towards the side of the affected eye, moving the eye away from the field of action of the affected lateral rectus muscle, with the aim of controlling diplopia and maintaining binocular vision.