A natural lens sits inside the front section of your eye, and as you age this lens may start to turn cloudy. This condition, called a cataract, will lead to progressively worsening vision.

The clear tissue at the front of the eye is the cornea; in order to have clear vision, the tissue of the cornea needs to remain thin and transparent. The inner layer of the cornea called the endothelium keeps the cornea clear, and if there is a problem with the cells in this layer, corneal edema may result.