Both seem correct to me without any real difference in meaning. Focused implies that your eyes are in that state already while focusing indicates that the process of getting focused may not yet have been completed. Splitting hairs, really.
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I would have thought this was a comma splice; that is, two main clauses are joined by a comma (rested is a finite verb in the past tense).It can be taken either way; I take it as a nonfinite participle.