[rmlew]

The battle of Manzikert was in 1071. By that time the Byzantine Empire has lost all of western Europe, all of northern Africa, and most of the Middle East. It occupied only the Balkan peninsula and Asia minor. It had lost about 80% of its former territory. I would not call losing 80% of your empire doing pretty well.
The Eastern Roman Empire never held Western Europe, that was the imperium of the Western Roman Empire It did occupy parts of Italy.

[stripes1776]

The Eastern Roman Empire never held Western Europe, that was the imperium of the Western Roman Empire It did occupy parts of Italy.

The capital was moved from Rome to Constantinople in the 4th century. Constantinople was the imperial capital of the entire Roman Empire.