Picture source: http://www.sxc.hu/photo/877183
As you can see in this picture, there is a lot of glare in this boy's glasses. Although it may be tricky, you can remove the glare using Photoshop.
Step One: The Tools
There are a couple of tools that people like to use to remove glare: The clone stamp tool and the healing brush. The shortcut for the clone stamp tool is "S" and the shortcut for the healing brush is "J". For both tools, you need to collect a sample area. Press the ALT key to select a part of the picture that you want to copy over the glare with. Ideally, you want the sample area to be very close to the affected area. That way the same color and texture is being copied over. It's important to take very short strokes and keep selecting new sample areas as you progress.
The clone stamp only fixes the affected area with the source sample. The healing brush takes some of the texture that surrounds the affected area and mixes it with the source sample. That is the only difference between the healing brush and the stone clamp tool. You should experiment with both because not every picture can be cured using the same methods from previous projects.
To effectively remove glare, you want to use these tools in very short strokes and the picture should be zoomed in to work more efficiently.
If an eye was affected by glare, I would copy the other eye to place over the glared eye and touch it up with the healing brush or clone stamp tool. However, both eyes are glare-free, so it is not necessary for me to make copied selections of an eye.
Step Two: The Process
Select the clone stamp tool and make a copied layer of the original. You always want to save your work to protect your project. You want to make the first copied layer to work with. Save the original for reference and backup.
Zoom in until you feel like you have enough canvas to work with. Your canvas should primarily consist of the glare and sample sources you can use to remove the glare. If there is too much glare, you may to select some copies of similar skin textures with the lasso tool to place over the glare. Since there are a lot of sample sources in this picture, I did not need to select copies of skin.
Make sure you zoom out once in a while to see how your work is going. You may need to backtrack and redo some parts. By now, I have used both tools, but I'm primarily sticking with the clone stamp tool. The healing brush is taking texture samples that do not mix well.
Make sure the new skin tone matches other skin tones around it. If it doesn't, the picture won't look authentic. You may want to lower the opacity of the clone stamp tool to help the skin tones blend and match.
Step Three: The Finishing Touches
About midway through it, I made another copied layer. It acted like a "save point." The boy's right eyebrow was the hardest to effectively fix since there was not much sample sources for it.
I used the healing brush for a couple of spots near the frame. For the most part, I just made sure that the skin tones were even.
Removing glare may be a little tricky for beginners, but with enough practice, it is possible. Not every picture can be treated the same way, so it's important to learn different ways to remove glare. One technique I did not use was copying other patches of skin or textures. This can be an effective way to remove glare as well.