Everything You Ever Wanted to Know About Dry Eyes
The subject of dry eyes and the associated symptoms is so vast whole books have been written about it, but today we’ll try to tackle the basics of an increasingly common problem for all ages.
What do tears do and why are they important?
The tear layer sits on the front of your eye, over the cornea and the white of your eye. It’s there to do several jobs – it lubricates the eyelids as you blink (if you had no tears it would be like blinking with two bits of sandpaper! Ouch!), it protects the eye from dust and particles to minimise irritation. It is also the first thing that starts the process of refraction to produce a clear image, because the light hits the tear layer before anything else. In addition, the tear layer allows the cornea to absorb oxygen.
The cornea (the clear bit over your iris and pupil) has no blood vessels in it, but its cells still need oxygen to stay healthy, so the eye diffuses it from the air, into the tears, then into the cells. (Aha! I hear you ask, what about when you’re asleep?! Well, at night it’s the same process but the oxygen diffuses through the thin vessels on the inside of your eyelids. At much lower levels but just enough to sustain the system while you’re asleep). So, you see, tears are essential for healthy, comfortable eyes, and good vision.
What are tears made of?
Tears are actually quite a delicate balance of three different types of fluid: The bulk of tears are made of water, but equally important are the mucous layer and the lipid (fatty) layer. The mucous layer sticks the tears to the front of the eye and stops them falling off and running down your cheeks. The lipid layer helps prevent the tears from evaporating too quickly, so both are essential to maintain a good quality tear film. An imbalance in these different layers is what gives rise to the many different types of problems associated with dry eyes.
What type of problems do dry eyes cause?
One of the most common problems we see are people complaining of their eyes ‘watering’, especially if it’s windy outside. It seems counter-intuitive to say this is a dry eye problem but technically that’s what it is. If your eye is missing the mucous layer then the cornea is exposed – the wind irritates the eye, so it responds by watering (as it thinks it has a foreign body in it), that water won’t stick, so the tears run off, and the problem spirals.
We often see people with intermittent blurry vision and uncomfortable eyes which can stem from the lipid layer being missing or inadequate. The watery layer evaporates, leaving the mucous layer, which as the name perhaps indicates, gives rise to smeary vision, varying with the blink (a bit like putting petroleum jelly on a camera lens).
People often complain of sore eyes, poor vision and eyelids being stuck together when they wake up in the morning. Assuming infection has been ruled out, this is again happening because the tears are inadequate. If you go to sleep with little or no tear film, what you have got evaporates overnight, and as you don’t produce tears while you’re asleep, you’re left with a mucous residue that stick the lids together and sore eyes as the eyelids haven’t been able to absorb much oxygen.
People with allergies, particularly hay fever, can have dry eye issues as they tend to over-produce the watery part of the tears which washes out the other layers, making the tears badly balanced and unstable.
All of these issues can cause uncomfortable eyes which can look red and sore depending on the severity of the problem. Blinking with reduced tears is a really big irritant and in very severe cases it can actually damage the cornea leading to potentially sight-threatening infection. Thankfully this is rare and the vast majority of people come and see us or their GP before things got to that stage.
What causes dry eyes?
It’s true that dry eyes are more of a problem in older people. This is because as you age you tend to produce a reduced volume of tears and lose elasticity in the eyelids: Droopy lower eyelids expose more of the part of the eye below the iris which not only increases irritation but more importantly, if the lid is falling forward the mechanical support for tear volume is lost and tears run off the eye.
Some medical conditions such as Sjogrens syndrome and other auto-immune diseases in the spectrum of arthritis can reduce the amount of tears we produce. Some medications, including some cancer treatments, also reduce tear production.
Most commonly though lid hygiene is a big factor: the fatty and mucous layers of the tears are produced by tiny glands on the inside of the eyelids just behind the line of the lashes. These ducts are very fine and are easily blocked, so if make up isn’t removed very well, or the lids aren’t cleaned very well, over time the ducts can get blocked with dead skin cells, make-up, dried tear residue etc. This obviously results in inadequate tear production and an unstable tear layer.
The lids can also be affected by something called Blepharitis, an inflammation of the edges of the eyelid which is again more prevalent in older people and leads to a dandruff-like appearance which blocks the ducts and affects tear production.
Environmental factors also play a part. With increasing use of screens, both desktop and handheld, people find themselves staring at these for most of the working day. Each time you blink, you refresh your tears, but when you stare at a screen your blink rate goes down, increasing the amount that the tears evaporate. But it’s not just air-conditioned offices – people on long drives often complain of dry, uncomfortable eyes after staring down the motorway for hours (although this can also be because they need specs!) We also see a spike in dry eye problems when the weather gets cold and everyone cranks the central heating up.
Finally, we have to mention Demodex. Demodex is a tiny mite which we all have on our skin, it lives in harmony with us and is harmless. However, it does like to hide in hair follicles, particularly eyelash follicles, causing inflammation and clogging up the lid margins. Don’t be horrified – we do all have them, and mostly they don’t cause a problem, but if there are too many present they can be the cause of a stubborn dry eye problem that keeps recurring as the mites multiply.
What can be done to resolve dry eye issues?
The best way to tackle dry eyes is to try and find out what’s causing it in the first place, which is sometimes very hard to pin down. An appointment with one of our opticians gives us an opportunity to really have a look at your tear layer and lids and see what the issue is. We can measure your tear break-up time (how fast it evaporates), the tear volume (how much there is and if it’s too thin) and see why it is the way it is: Most of the time there is no one clear answer or treatment, and in some cases, while the problem cannot be ‘cured’, it can often be very well managed.
Options include hot compresses to clear blocked eye ducts, eyelid wipes to remove blockages and kill any mites that are present, drops to re-balance the tears, lifestyle and health advice. There is some evidence to suggest some vitamin supplements can increase tear production, and for some chronically blocked ducts, steam treatments are sometimes used. Sometimes just understanding why something is happening can make one feel better and remove some of the frustration felt.
If you have any of the issues detailed above don’t hesitate to come and see us at any of our branches. We have specific dry eye consultation appointments available where your optician will focus on dry eye issues and help you find ways to improve the symptoms. Pop in or give us a call.
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