OK. If you are loading the LaFemme character into the scene as is, it is NOT using the SSS with Refracted Eyes shader in that case (that is the one that causes the eyewhites to preview white like that.) The OTHER tipoff that you aren't using the SSS with Refracted Eyes shader is that you can, at least, see a little black pupil in the preview when that shader is used.

For the record, LaFemme loads with the Procedural SSS shaders (you can find three different material sets in the Materials folder ... RPublishing > LaFemme)

This is why this screen shot was helpful in figuring out which one of the two things was causing it. I suspect it's something to do with transparency - either in the material, or in your Firefly preview settings. Because the tear line just above the lower lid is also showing opaque. If you haven't touched the material settings at all you should be able to preview the eyes fine.

So ... we will start by checking your firefly preview settings. Choose Render > Render Settings, and then select the Preview tab. Can you take a screen cap of your preview settings? Here are mine (I'm using a GeForce GTX 1080 in this case)