The four respondants to your question have all made some good points. However, as a dry eye specialist, I thought I might just crystalize the science. For lots more information on this topic feel free to visit our website www.dryeyecentre.com.au.
1. If you have persistent weeping eyes, you should forget about lubricating eye drops. They are most unlikely to help. The brief reasoning behind this is that historically, we believed (incorrectly) that all dry eye problems (of which weeping eyes is just one type) were mostly due to not enough watery tears. Indeed, most of the early eyedrops including many that are still on the pharmacy shelves today, are basically replacement drops for the watery part of our tears. That's ok if you have water deficiency! However, the evidence now suggests that we were wrong about all that. In fact about 85% of dry eye disease has nothing to do with insufficient watery tears! So if you're part of that 85% of people you can forget about water replacment eye drops! Not to mention that many of these eye drops have a nasty little preservative in them called BAK (benzalkonium chloride). This horrible preservative destabilizes the corneal surface leading to increased inflammation and guess what....more dry eye!!
2. Let' s just say then, that you share your condition with the 15% of people that do actually have a watery tear deficiency. Well, it would seem a little contradictory, since your tears run down your face right? But let me explain. I noted you said that your mouth has been dry for a few years. I find this interesting. Here at the Dry Eye Centre, our clinic is full of patients who never realised that their dry eyes could have something to do with an underlying autoimmune problem. Autoimmune disease is now believed to be the trigger for the other 15% of dry eye (and yes, the type where some patients derive benefit from water replacement eye drops). If you were my patient, the first thing I'd be doing with you is giving you a list of our preferred blood tests to look for autoimmune and thyroid problems. With a dry mouth, I'd especially be interested in Sjogren serology. If these tests returned any positive findings, I'd be looking at a quite different managment plan for your problem. And about the contradiction with tears running down your face? Well, ocular surface science is complex. However, autoimmune diseases can disrupt both the watery tear production as well as the ocular surface itself. Therefore, it doesn't necessarily mean you have no watery tears. However, if the ocular surface is destabilized by an autoimmune condition, there may be nothing to hold the watery tears in place. In some patients with autoimmune disease, watery tear production is also impared. Finally, on this point, you should not worry about the prospect of autoimmune disease. After all, if we're just talking dry eye, there's an 85% chance it's not! and the dry mouth could be due to the Endep.
3. Yes some medications can cause dry eye / mouth problems. Endep can cause both, though we don't know the exact likelihood. You should never, stop your medication without professional advice, but you could discuss this with your doctor. And yes, if there is no underlying autoimmune problem, then this could be the cause of dry mouth.
4. Finally, that 85% of dry eye patients I mentioned? If they don't have a watery tear deficiency, then what do they have? Well the tears are made up of three layers. I've already discussed the watery part (called aqueous) and the inner layer (mucin) is not for this discussion. However, the outer layer is an oil called "lipid" or "meibum". This is where the problem origintes for 85% of dry eye sufferers. The meibum arises from tiny glands on the edges of the eyelids just behind the eye lashes. For lots of reasons these glands become blocked. This is a problem, because the meibum is needed to sit on top of the watery aquous layer, to stop it from evaporating or running down your face. Have you ever poured oil on water? if you have you'll know it floats! If there's no oil the water dries up (or runds down your face). If your glands are blocked, there is a range of treatment options which we offer to unblock them and educate you in the future maintencance of them. So if, the tears are running down your face, what about the newer generation oil replacement eyedrops like Systane Balance. After all it's meant to replace the oils! Well the problem is that all these eye drops are just bandaids. For short-term use in the mildest of cases they may help, but they do not permanently alter ocular surface biochemistry in any good way, and as for those preservatives.....So the only way to deal with blocked glands is to clean them out, including the drainpipes (as one respondant suggested). You must deal with the root cause, or in most cases the condition will progress and symptoms continue or even worsen.
Here at the Dry Eye Centre, we use advanced diagnostic techniques to investigate the health of the whole ocular surface, taking a holistic approach, we apply the the most advanced evidence based diagnostic and treatment procedures available.