From the end of the 7th century until circa 10th century AD, Chios shared the descent and economic decline of the areas in Asia Minor and Greece. The recovery of the island began mainly at the 11th century AD. the fortress were probably built then, while the chrysobull of Emperor Nikephoros Botaneiates (1078 - 1081) mentions numerous administrative and military officers. The presence of royal officers, fortress builders and guards indicates the interest of the capital city in defense works on the island. According to Anna Comnena, Chios experienced the attacks of the Turk Tzachas during the of the 11th century, at 1090 but at 1093 the Byzantine General Constantine Dalassinos drove Tzachas from Chios.
In 1124 and 1171, the Venetians tried to conquer the island, but abandoned Chios after a famine broke out , and rumors that the Byzantine fleet was on its way to Chios had spread on the island.
After 1204, Chios became subject to the Latin state of Constantinople, but was liberated by Duke John Vatatzis in 1225. After a series of adventures, the Genoese conquered the island and held it in their possession for approximately two centuries.
Reference
http://www.chiosonline.gr/byzantinechios.asp