Loss of vision in these cases can be temporary but often is permanent. The human eyeball measures less than one inch in diameter. It is not completely round but is shaped more like a slightly flattened ball. The size of a normal eye differs only a little from person to person but can appear very different depending on the structure of each individual's eyelids. The surface of the eye bends light rays, focusing them on the retina and enabling us to see clearly.
Light rays bend as they pass from air outside the eye to the fluid within the eye.
When someone's eyes are open underwater, the density of the water at the surface of the eye is similar to that of the fluid inside the eye. This decreases the ability of the eye to bend light rays to a focus, and vision is blurry. Wearing a diving mask keeps air in front of the eye, which provides an air-fluid difference and enables the diver to see normally. The General Eye Clinic is located in the Eye and Ear Infirmary at 1855 W. Taylor Street, Chicago IL 60612.