Zoom in on the eyes and using the Selection tool on the Polygon setting, select the whites of the eyes. Press the Gamma Correct (+) button twice and the Contrast (+) button once. Do the same for the rest of the whites of the eyes.
If there are harsh lines after you brighten the eyes, then use the Blur tool on the precise setting to blur them away.
Using the Selection tool on the Circle setting, select the colored part of the eyes and go to Adjust >> Brightness and Contrast.
Again if it’s too harsh around the eyes once you do that, blur away the rough edges.