The normal eye is kept moist by a thin film of tears on its surface. Most of these tears are produced by glands under the upper lid and are spread across the cornea with each blink. If tear production is reduced for any of a variety of reasons, you will suffer symptoms of hot, burning, dry eyes. In very severe cases, the cornea may dry, become cloudy and affect your sight.
This is one of the conditions which your optometrist looks for during an eye examination. If indicated, he can perform a simple test to determine the amount of tear fluid you have. If the amount is moderately low, you can gain comfort by using drops of artificial tears. For a critical shortage, a soft contact lens may be indicated to keep the eye moist.
A dry eye can also result if the tear production is normal, but the blink reflex is missing. When this occurs, tears cannot be spread across the eye.
An optometrist does much more than prescribe vision correction for eyes; he or she checks to see that the eyes themselves are functioning properly.