Many people have more difficulty seeing clearly at night than they should. This condition is called Nyctalopia in which the retina does not regenerate a pigment called visual purple. This purplish-red pigment prevents night blindness but can become bleached out when the eyes are exposed to strong sunlight or if the retina is deficient in vitamin A.
This condition should not be confused with the normal reduction of vision we all experience at night. The reason for this is that as the light gets less, the pupil (that little hole in the center of the eye) opens wider to allow more light to enter. As photographers know, the smaller the aperture, the sharper the picture. So when the pupil gets larger, the “picture” is not quite as sharp.
Not sure? Your optometrist can measure your dark adaptation and determine if you have night blindness. He may prescribe sunglasses to block out infrared rays of the sun or may suggest an increase of vitamin A in your diet.
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.
These programs are presented for reference only. Please do not substitute, disregard or delay seeing professional medical advise based on the information presented. Call your doctor or emergency medical services immediately for any medical emergency.
THE IMPORTANCE OF COMPLETE EYE EXAMS
DRY EYE: TEAR OSMOLARITY
AGE-RELATED MACULAR DEGENERATION (AMD)
OCULAR ALLERGIES OVERVIEW