Making Tears Part 5
In previous sections of this series, we’ve learned about some of the many proteins and salts making up our tears - but we have yet to discuss where (and how) we get the water. It should be obvious that every element of our tears ultimately comes from our diet and digestion (and the many, tiny germs relevant to that digestion process) - and no surprise that the water comes through our gut as well. I’ve covered much of this in prior posts, but how do the tiny cells in our lacrimal gland and scattered over the smooth membranes covering portions of the eye and eyelids ultimately regulate and produce that water? Remarkably, scientists continue to be befuddled by this process, but much has been learned from studies (largely using rodents). I’ll use some artistic license around my medieval analogies to help explain what I know about this interesting process.
Remember those salty “tokens” we called sodium and calcium “ions?” These tiny, “charged particles” have an electrical nature which allows them to bind and then “flip switches” in cells. Pathways open, allowing materials like water to pass through otherwise watertight membranes - and water likes to follow these ions - so cellular “pumps” can be triggered and run by these tiny tokens. Scientists refer to this production of water as “transepithelial” - indicating that the water literally passes through these (epithelial) cells and around or through the binding agents acting as the “mortar” between these cells. Of equal interest is that there are “protein factories” inside these cells that make the products (like Lactoferrin and Lysozyme) which can be transported into the water that becomes our tears.
Flow is a highly regulated process involving the “telegraph wires” (a neural network), as well as local and distant messengers (proteins and hormones). Some merely open or close the “aqueducts” (blood supply), so more water is delivered to the tissues. The “S and PS camps” (Sympathetic and Parasympathetic Systems) are good at this part of the regulation and many drugs have activities in this realm. A good online source for finding medications related to the “S” camp can be found here: https://go.drugbank.com/categories/DBCAT000438 but the effects are complex, as these messengers not only increase circulation, but also may stimulate muscles which open lids further (those knights on horses pulling the carriage around), which will expose the eyes to evaporation (and drying out). The “S” camp is also primarily responsible for the “fire hose” or emergency backup system making the salty tears we actively cry with (the buckets of fire-prevention water we make when sad, when something gets in our eyes or when the sprinklers let us down). The “PS” camp has an equal resource here: https://go.drugbank.com/categories/DBCAT000448 and is generally responsible for the "“sprinkler system” making the “salad dressing” of a healthy tear.
It is not uncommon for me to find dry eye patients on dozens of medications, treating a wide range of symptoms and maladies. Some of these drugs are countering side effects of one another, which can relate to these 2 opposing “camps.” Sorting out which medications are truly necessary - and weeding out those that are less necessary (or only used as counters to side effects that disappear when those medications are weeded out) often requires input from the various doctors who prescribed them - so it can take a literal “village” to help an average dry eye patient. Our eyes, like our bodies, are a complex chemical factory, with all the general issues for successful survival and flourishing, as those “medieval realms” - adequate nourishment, rest, support, protection and order. Without proper elements of each, chaos and “plagues” can take us down. More on this internal and external regulation next time!
To schedule an appointment with Dr. Jaccoma, call Excellent Vision at either of these two dry eye offices:
(1) 155 Griffin Rd, Portsmouth, NH 03801 (603) 574-2020
(2) 3 Woodland Rd, STE 112 Stoneham, MA 02180 (near Boston) (781) 321-6463