I tried to reproduce the artwork exactly as what I saw but still based on the primary eye structure. I used the eyedropper tool to pick the color from the artwork and brush tool to paint on the photo (sorry that I did not record the exact brushes or settings that I used, but it could probably be 27 brush with 50% spacing for clouds in the sky and 25 straight brush for the other strokes). Note that I cropped the photo to match the part shown in the artwork. Besides, on the left side of my work, somewhere below the middle, I left the medial canthus unpainted as a proof of the original photo used.