There are basically three main reasons for dry eyes - not enough tears coming out of the faucet, imperfect tears that don’t lubricate well, and defective eyelid “windshield wipers” that don’t flush the surface properly.
In the old days, doctors thought that dry eyes were mostly due to deficient tear production, and so artificial tears were all that was needed. But it turns out that inflammatory causes are more common than simple tear insufficiency, so the solution can be more complex than just recommending an over the counter eye drop.
The solutions to the three types of problems differ, so you will need an eye doctor to sort out the cause first. While some eye surface issues can be identified by direct observation (that’s fancy words for “just looking”), often there are particular tests needed to determine the correct diagnosis.
Tests to quantify how much tears your eyes produce include the Schirmer tear quantification test and the tear osmolarity test. The stability of lubrication is measured by the Tear Breakup Time (TBUT), and symptoms scored on the Ocular Surface Disease Index (OSDI). Matrix metalloproteinase levels are very useful in identifying tear problems due to inflammatory disease.
Tears are mostly composed of salt water, but the stability of tears on the eye surface is mostly related to tiny amounts of oil and mucus. The mucus and oil secreting glands of the eyelid thus become critical components of ocular surface health.
Specifically, the oil portion is derived from meibum secretions from the eyelid Meibomian glands, which are located next to the eyelashes on the lid margin.
Inflammation raises the melting point of meibum, so that eyelid gland secretions thicken like toothpaste, when they should flow like olive oil. This is the basis for using warm compresses, heat masks and Intense Pulsed Light (IPL) to help melt and soften meibomian gland secretions. Omega-3 fatty acid supplementation is often useful to reduce the associated inflammation.
Not all eye doctors are attuned to the complexities of dry eye diagnosis and treatment. Frankly, not all eye doctors will take the time to figure out the causes and best treatments for dry eye patients. Part of the reason for this is that dry eye symptoms are often frustrating and difficult to eradicate. There’s also no glasses to sell or surgery to recommend, so the best dry eye doctors must be more patient than bottom line-oriented.
Benjamin H. Ticho, MD