When I had fastened my eyes (atenisas). This personal touch Peter adds from his own experience. See Luk 4:20 and Act 3:4, Act 3:12 for this striking verb atenizō, to stretch the eyes towards, first aorist active participle here.
I considered (katanoeō). Imperfect active of kataneoō to put the mind down on, to ponder, I was pondering.
And saw (kai eidon). Second aorist active indicative, saw in a flash.