How do you know if you have evaporative 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.
By far the most common type of dry eye disease is evaporative dry eye. As explained in the prior blog post (please read before continuing here), there are 2 types of dry eye disease, aqueous deficient and evaporative. However, 83% of all dry eye patients have an evaporate component to their dry eye. This means that you may be producing plenty of tears, but because the quality of the tears are low, they evaporate way too fast. This negatively affects your eyes in a few ways. First, your visual clarity will likely suffer. The first part of your eye that an image hits is your tear film, and 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, on the computer, or any other visually demanding time, there is a high likelihood that you are suffering from evaporative dry eye. Second, 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. Finally, 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 they send a signal to the brain, saying “we are dry, we need more tears!!” The brain responds by dumping more tears on your eyes, causing your eyes 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, and record how long it takes for your tear film to evaporate between blinks (Figure 1: NITBUT photo)
Ready for some tear film science? Good, me too! To simplify, there are 2 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 layers keeps the tears from evaporating too fast. We have oil glands called Meibomian glands that are located in our upper and lower eyelids, and their openings are right on your water line, 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 (Figure 2: Meibomography photo),
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 little blood vessels called telangiectasia that we can image in our office (see figure 1 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. Further, 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.
Fortunately, at Peak Eyecare we have numerous at home and in-office treatment options that we can deploy to keep your meibomian glands happy, healthy, and functioning well for years to come. Stay tuned for the next blog post as we discuss these in depth.