The cornea is the clear, round window of tissue that covers the iris and lens of the eye. There are five layers to the cornea, the innermost being the endothelium (read about corneal anatomy here). This layer is made of a sheet of endothelial cells and is essential in keeping the cornea clear. They accomplish this by working as a pump to keep a regulated amount of water in the stroma (the middle layer of the cornea).
However, in a diseased state like Fuchs’ corneal dystrophy, the cornea can be cloudy, interfering with the ability of the cornea to focus light as it enters the eye. This can result in blurred, clouded vision that can diminish our ability to see clearly.