There is some degree of eye size change possible with Photoshop, but its success depends on each individual person. And there are limits to what it can do without looking grotesque. For many of us, our eyes squint more when we smile, it’s an involuntary reflex and also very much a part of a smiling face. In Photoshop I have successfully swapped someone’s own more-open-eyes from an adjacent shot and combined them with the overall shot that looks best but has squinty eyes. When done carefully, it’s undetectable. When I propose doing this for a client, I provide a side-by-side rough draft comparison for you to see and approve before going ahead with such a plan.