First and foremost, open the image you wish to fix and take a few seconds to assess the issues you have with it. Here I'll use an image that my friend had asked me to take for her blog. Admittedly, it's not the best photo when it comes to having a bright cornea thanks to some pretty significant cloud coverage that day (and a mesh curtain filtering the overcast) - but don't you worry, we'll fix that stuff up with no problem!
(Fact: The cornea is the name for the white of your eye - now you know!)
In this case, we will brighten the image over-all a little. Sure, we could just go ahead and brighten the cornea, but chances are that would make the eye come off with a very unnatural feel to it. So go to Image > Adjustments > Brightness/Contrast. Here's what the menu item looks like:
Now when you click on the menu item, you'll be greeted by a set of sliders and a few check box options. Here's what those will look like:
The goal of using the brightness and contrast window is to get an overall better brightness to the photo, which shouldn't be terribly hard to do! Just slide your brightness and contrast options up until you find something that looks good. Mine is around Brightness 15 and Contrast 21. As you can see, the cornea is already significantly brighter. This means less work for us to do later on!
Of course, thanks to insomnia, I've still got a bit of bloodshot-chic going on, and we just can't have that! Here's where it gets a bit tricky, but if you learn the technique, you can fix almost any color problem you might run across! Grab yourself a soft edge brush that fits comfortably inside the cornea of the eye. For me, that happens to be a 35 pixel brush.
The first thing we need to do is lighten the red areas to the same shade as the white of the eye around it. Turn your brush opacity to 30% and set the mode to Luminosity. What this does is increase the lightness of the eye gradually without altering any colors just yet.
Now, all you have to do is hold down ALT and click on an area of your image to select the luminosity (brightness) of the surrounding white area. Here is where I clicked to give you an example!
Brush around the discolored areas (gently!) to lighten them up a little. Remember that eyes have a shape to them, so don't try to make the areas at the edges or areas that are shaded naturally as bright as highlighted areas. This will give the eye a flat, unnatural look, and people will know that you've been touching up your pictures! You may have to change your luminosity point several times while doing this. Just try to match the brightness of the image as best you can. Here's what my end result looks like. It might look a little strange now, as the inside edge has appeared to turn bright pink - but we'll work on that, don't worry!
Now we have to correct the color, which is done in a strikingly similar fashion to correcting the luminosity. Set your brush mode to color, now, as we've got to fix that bright pink edge!
Hold down ALT and click an area with the correct color that you need to apply to the discolored areas. Here's where I clicked:
Now just brush away that weird pink color, and voila! The white of the eye has been corrected in a very quick and simple way! Here's my before and after, as you can see we end up with a whiter, brighter, and much more clear eye! Just make sure that you're happy with the effect before you save, because if not, now is the time to go back and change it! You can see how beneficial it is to use Photoshop. Fixing white eye issues have never been easier!