The Yin/Yang of Ocular Surface Disease – Tear Production and Tear Loss

Ocular Surface Disease
Ocular Surface Disease

Dry eyes – so common yet so misunderstood. Worldwide, over 330 million people suffer from dry eye symptoms, including approximately 30 million in the US, of which only 16 million have been actually diagnosed by their eye care provider.

Though there are five FDA-approved medications available for the treatment of dry eyes, only about 2 million patients use these. Most either depend on OTC lubricant eyedrops or simply endure their symptoms.

The Causes of Dry Eyes – Tear Production and Tear Loss

Understanding dry eyes requires knowing what causes symptoms. While there are many other “causes” of dry eyes – including autoimmune diseases, medication side effects, anatomic lid abnormalities, and more – there are two that are vital to understand.

Dry eye causes can largely be divided into two major categories: reduced production of tears by the lacrimal gland (located under the upper eyelid towards the outside edge) and increased loss (evaporation) of tears from the eye surface.

Decreased tear production is easier for patients to understand. Though the reasons can be many – including side effects of medications, systemic diseases, and more – the base concept is simple to grasp.

Excessive tear loss is harder for some to understand. There are “drains” at the inner corner of each (upper and lower) eyelid called “puncta,” where tears flow during the process of blinking and drain through tiny tubes down the back of our throat. This is why we can “taste” medication eye drops that may be applied to the eye.

Our eyelids are supposed to close during each blink, but often they do not actually do so. Anatomic problems can develop, causing eyelids to rotate inward or outward, leading to incomplete closure. Many people’s eyelids do not fully close when they sleep, allowing tears to evaporate from the exposed surface all night long. During the day, “incomplete blinking,” where the eyelids do not fully touch also leads to faster evaporation. Along with being common, incomplete blinking is a challenging problem to correct.

Effective treatment of one cause of dry eye but not the other often fails to achieve relief of symptoms. Think of it this way: if your car has no gas and flat tires, filling up the tires with air will not mean you can drive again. Similarly, for our eyes, each problem must be treated to achieve comfort.

Updating Dry Eye Treatment Strategies Through Reframing

For most patients, reduced production of tears is NOT the primary problem. As a result, the phrase “dry eyes” can confuse what is actually the core issue.

Some patients report dry eye symptoms such as burning, stinging, or grittiness but also note that their eyes water excessively. How can eyes be both dry and wet?

By moving away from the “dry eye” label and reframing the condition, it’s far easier to give the situation proper context. Often, if the composition of our tears is not “healthy” (for example, it may have deficient amounts of oil or mucin – more on this in other segments), irritation can cause “reflex tearing” as our bodies attempt to wash away the offending tear film. The eye is experiencing dry eye symptoms while also dealing with excessive watering.

Choosing another label for the condition can make a difference, alleviating confusion caused by the term “dry eye.” That’s one reason some prefer to call this “ocular surface disease,” even though dry eye is a more commonly used phrase.

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