For eyes, it's 3 things.. catchlight and gleam, the 3rd is, though not always present, make-up.
For normal portraits, to make the eyes look alive, a catchlight will do fine. In Photoshop, choose a soft edge brush and adjust the size to a very small spray. The opacity should be around 60-70%. Choose the color white and just dab a little in the eye/ iris. Play around with the "FLOW" and the "OPACITY" to get the effect.
Oso, if the white balance is offwhite and the white area of the eyes is slight yellowish, you can lasso the white areas and use curves and levels to make it slightly whiter.