What is Evaporative Dry Eye Disease?

By far the most common type of dry eye disease is evaporative dry eye. Approximately 83% of all dry eye patients have an evaporative component to their dry eye. The most obvious symptom of evaporative dry eye is blurry vision that gets better after you blink. Most patients also have irritated, red, dry eyes, while others may actually have the symptom of watery eyes.

This means that you may be producing plenty of tears, but because the quality of the tears is low, they evaporate way too fast. This negatively affects your eyes in a few ways:

• Decreased Visual Clarity: The first part of your eye that an image hits is your tear film. If your tear film is disrupted, you will have intermittent blurry vision no matter how perfect your glasses or contact lens prescription is. If you find that your vision comes in and out of focus when driving, working on the computer, or during any other visually demanding task, there is a high likelihood that you are suffering from evaporative dry eye.

• Irritation and Redness: Evaporative dry eye makes your eyes feel irritated, dry, and appear red. Your tear film is not adequately protecting the cornea, which has one of the highest concentrations of nerve endings in the body.

• Excessive Watering: Evaporative dry eye can lead to the perplexing symptom of watery eyes when you actually have dry eyes. If the tear film evaporates too fast, your eyes feel dry and send a signal to the brain, saying, “We are dry, we need more tears!!” The brain responds by dumping more tears onto your eyes, causing them to water. However, these tears are still of poor quality, evaporating too fast and continuing the signal cascade to the brain. If you find that you are constantly wiping tears away from your eyes—except when watching a sad movie—you are likely suffering from evaporative dry eye.

We can test this directly by focusing a microscopic video camera on your tear film to record how long it takes for your tear film to evaporate between blinks (Figure 1: NIKBUT photo).

Ready for Some Tear Film Science?

Good, me too! To simplify, there are two main layers in your tear film: an oil layer and a water layer. The oil layer forms a protective outer barrier for the water layer, much like looking at an oil slick on a puddle on a rainy day. This protective oil layer keeps the tears from evaporating too fast.

We have oil glands called Meibomian glands that are located in our upper and lower eyelids. Their openings are right on your waterline—the 1-2mm area on your eyelid between your eyelashes and your eyeball. During our routine Dry Eye Exam at Peak Eyecare, we image these glands using an infrared camera. We then compare your glands to a normative database, where we look for early signs of gland atrophy and adjust our treatment recommendations accordingly.

• In a healthy eye: These meibomian glands produce an olive oil-like substance called meibum during every blink, and this meibum forms the protective oil layer on your tear film.

• In Dry Eye Disease: These oil glands are surrounded by inflammation, which is seen as small blood vessels called telangiectasia that we can image in our office (see Figure 2 of one of our patient’s lids).

This inflammation can lead to clogging of the meibomian glands, which changes the meibum from an olive oil consistency to a toothpaste-like consistency. This thick clog prevents the meibomian glands from releasing the protective, essential oil that the tear film needs for stability. Furthermore, if these meibomian glands remain clogged for a long period of time, they can start to atrophy (die off), and once they atrophy, there is no way to regenerate them. Our goal is to never let these glands die off, because if they do, your dry eye symptoms will get drastically worse, and there is little that we can do at that point.