Yes, certain people have a high level of protein in their tear film. If you have contact lenses in, then the protein sticks to them and forms a whitish layer. Here's how lifetips.com describes it:

"Protein buildup often occurs when contact lenses are worn beyond the recommended durations or not cared for properly. Additionally, some people are just more prone to producing protein buildup on their contact lenses than others. Either cause of excessive protein deposits should be taken seriously because they can have damaging effects on the eye. The mildest effects include dry eyes and minor discomfort but protein buildup can also lead to allergic reactions, infections and diminished vision in more severe cases."