Some say their vision is poor or fluctuates throughout the day. These fluctuations are directly related to dry eye. The tear layer on the eye is the front focusing (refracting) surface, if it is irregular or incomplete it will impact vision.
The following is a picture of an eye with a very irregular tear film:
This is a view from the microscope (called a slit lamp) of a patient with dry eye. The yellowish appearance comes from flourescein dye doctors put in the eye to visualize the tear film. Notice that the lower half is not a smooth color. It has dark spots and lines which are areas where the tears are breaking apart.
After blinking a normal eye should be smoothly and uniformly covered with tears for about ten seconds. With a dye in the eye it would appear as a smooth yellow tear layer. This is a dry eye patient about 2-3 seconds after they blink. Almost immediately the protective tear layer is breaking apart, exposing the corneal surface and degrading the quality of vision. This test performed by your eye doctor is called a Tear Break Up Time, or TBUT test. A normal score is 10 seconds or more. Less than 10 seconds and you could start having some dry eye problems.
Dry eye treatment is primarily focused on increasing the quality of tears and the amount of time they stay on the cornea. For information on dry eye treatment please visit dryeyeknowledge.com.
