Father Isaac (Antimonov), who came of a line of rich Kursk merchants, entered the Skete of Optina in 1841, at about the same time as Father Ambrose. He was ordained to the priesthood, notwithstanding his reluctance, and recommended to the holy Metropolitan Philaret of Moscow by Starets Macarius to succeed Father Moses as Abbot of the main monastery in 1862. With great faith, and obedient to divine Providence, Father Isaac forsook his beloved hesychia, to spend over thirty years occupied with extensive and much-needed building works and with restoring the monastery’s economic stability, which Father Moses had neglected. He relied on the discernment of Starets Ambrose and asked his advice on every matter of importance. For all his great responsibilities, he remained humble and simple with his brethren. On Saturdays, when he went for confession to Father Ambrose, he would wait his turn with the other visitors. He hesitated for a while before backing the foundation of Shamordino. When Starets Ambrose went to live there permanently, he did not disguise his disappointment. Even so, he resolutely took up the cause of the Convent when the Bishop wanted to sever its connection with the Monastery of Optina. The withdrawal of Father Ambrose marked the beginning of a time of trials for the monastery. Father Isaac himself was stricken by paralysis, and only recovered some strength during the last year of his abbacy. In the end, he fell ill with dysentery and gave up his soul to God while deep in prayer on 28 August 1894, at the age of eighty-five.

Source:

http://stpaisiusmonastery.org/about-the-monastery/life-of-st-paisius/optina-elders/