In "God's Word for Today" Steve Oliver writes:
Christ's majesty is not simply a matter of a glorious appearance (though He certainly has that). Rather, it is a visual display of His genuine power and authority. In John's vision, each visual aspect of Christ displays an invisible attribute of Jesus' character, power, or authority. For exam-ple, the depiction of Christ's eyes “as a flame” indicates that He sees and understands everything, that nothing is hidden from Him. If we are in trouble, this is a comfort. If we are try-ing to excuse ourselves for wrongdoing, this is troubling.
Source: Christ, the Triumphant Lord: Adult Teacher's Insights, page 5.