As discussed in previous blogs, there are 2 types of Dry Eye Disease, Aqueous Deficient Dry Eye and Evaporative Dry Eye. We have discussed both the causes and treatments of Evaporative Dry Eye in length, so in this blog we will be turning our attention to Aqueous Deficient Dry Eye. This form of dryness is due to your ocular system not producing enough tears.
What Causes Aqueous Deficient Dry Eye Disease?
There are 2 types of tears that your eyes can produce, Reflex tears and Basal tears. Reflex tears occur as a response, or reflex, to an outside factor, such as a foreign body. Common foreign bodies that I see among my patients is dirt, an eyelash, a small piece of metal when grinding without eye protection, or even coal from the train. These produce immediate and excessive tearing as the ocular system does all that it can to flush this object out of your eye. While reflex tears serve an important role, they are not tears that play a role in Dry Eye Disease.
Basal tears are the tears that your body produces on a consistent basis to keep the front surfaces of the eye (the cornea and conjunctiva) lubricated and healthy. Without constant production of basal tears, your cornea would dry out and scar over, causing pain and a permanent loss of vision. Basal tears also contain anti-microbials, which kill the many microscopic organisms that constantly bombard the front surface of our eyes throughout the day. These tears are secreted from the lacrimal glands, which are located behind your brow.
As your tears evaporate, your lacrimal glands produce a steady supply of basal tears. At Peak, we can evaluate your tear production by taking a photo of and than measuring the height of tears that are resting on your lower eyelid between blinks. This is called the tear meniscus height (Figure 1 above). However, inflammation of the lacrimal glands can cause of decrease in basal tear production. The most severe form of this occurs in Sjogren’s Syndrome patients, where there is a deficiency in the production…. Throughout the body, including the mouth and eyes. Most patients with Aqueous Deficient Dry Eye do not have Sjogren’s Syndrome, but rather have general, less severe inflammation of their lacrimal glands, which decrease the amount of basal tears that they produce. This leads to irritated, red, gritty-feeling eyes. If left untreated, the cornea can become more and more damaged, eventually leading to permanent scarring.
Please read the next blog post for how to best treat Aqueous Deficient Dry Eye.