In addition to blepharitis, dryness of the eyes is one of the most common problems I see. Dryness falls into two categories- vision threatening where scar tissue blocks vision and must be vigorously treated, or annoying where treatment is only needed to control inconvenient symptoms. In my practice the former is extremely rare but the latter is extremely common. Patient complaints include irritation, blurred vision, and excess tearing. These may be expreienced in any combination, or individually in surprising ways.
For example, how can one experience excess tearing when the eyes are dry? Our body produces tears in two ways. The first is from small glands all around our eyes that constantly produce small amounts of tears that are mainly responsible for regulating the minute to minute moisture on our eyes. The second source of tears is from a gland beside each eye called the lacrimal gland, which produces large amounts of tears when needed- for example when we cry or get something in our eye and need a lot of tears to wash it out. So the excess tearing in dry eye occurs when the small glands don’t produce enough, the eyes get irritated, and the lacrimal gland kicks in with a flood of tears. Easy enough to test for- just put lubricating drops from the drug store in regularly and if the excess tearing clears up you know the answer. If it doesn’t get better, the tear drainage system may be blocked and I’ll talk more about that later.
Patients are also often surprised to learn that their blurred vision, without any irritation, is from dry eye. I often see patients for emergency vision loss in the late fall when the weather gets colder, the heat comes on, and the air gets drier. Or after patients have taken an antihistamine like Claritin which dries the eyes. The most important part of the eye for focusing incoming light is not the lens, but the tear film- the reason is complicated- it relates to differences in indices of refraction. But the result is that tiny changes in the consistency of the tear film can result in large changes in the focus of the eyes and hence blurred vision. Again, consistent lubricating drops solve the problem. Another time we commonly see blurred vision from dryness is when using the computer or when reading. This is because we don’t blink as often when we are concentrating on these tasks, and our eyes get drier. Typically, these patients feel their vision is fine when they start, but after twenty or thirty minutes of using the computer or reading, their vision blurs. Putting an artificial tear drop in before starting these activities, and then regularly, helps.
Irritation and redness, though, are the most common complaints about dryness. When patients complain about irritation of their eyes, they are often surprised that we make a big deal out of whether the irritation is worse in the morning or later in the day. Irritation late in the day is most likely due to dryness since the eyes are open all day, the tears evaporate, and the eyes get drier as the day goes on. If the eyes are more irritated first thing in the morning, a common possibility is a condition called lagophthalmos in which a patient sleeps with their eyes partially open and the eyes become drier through the night. Sleeping under a ceiling fan or an AC/heat vent that blows air across the eye obviously makes this worse.
Sometimes, the condition of dry eye can be associated with other health disorders. The most common is called Sjogrens syndrome which includes dry eye, dry mouth, and arthritis.
How do we diagnose dry eye?
I am often asked by patients how I know their eyes are dry. The diagnosis is made mostly on the basis of the patient complaints and a trial of artificial tears to see if the complaints improve. But there are other things we look for. One is “debris” in the tear film. Normally the eyes produce enough tears to wash away the dust that is always getting onto the surface of our eyes. When we examine the eye with a microscope (slit lamp), if we see particles in the tears, we know the eyes are dry. We also look for how quickly the tear film becomes disorganized after blinking. Normally after blinking, the tears form a clear film over the surface of the eye. If the eyes are dry, the film forms, but only for a few seconds and then it breaks ups- the difference is like driving in the rain with your windshield wiper on. The normal is a clear windshield between swipes, dry is like having a leaf under the wiper. We see this best with the help of fluorescein, a water soluble dye that we put into the eye. This is the “orange stuff” that you get during an eye exam (it is also used to check the pressure in the eye). A more serious form of dryness occurs when there are actual dry spots on the cornea that are highlighted with this dye.
Other tests that can be done, mostly to verify the diagnosis with objective “data” so that an insurer will pay for some of the treatments (see below), are the Shirmer’s test, in which the production of tears over a period of time (usually five minutes) are collected on small paper strips to measure the quantitiy of tears made, or enzyme assays performed on tear samples.
How do we treat dry eye?
The mainstay of treatment of dry eye is the use of non prescription artificial tears. In mild dry eye, these can be used on an “as needed” basis, but work best if used proactively to prevent symptoms. For example, my own eyes get dry every day about 4 PM. If I put an artifical tear drop in at 3 PM, I go the rest of the day symptom free. If however, I miss the 3 PM drop and put a drop in a 4 PM when my eyes have become irritated, I must put another drop in at 4:30, 5:30 etc, and my eyes never really get comfortable until I start over the next day. Generally, if the eyes are moderately dry, drops 3x/day (mid morning, mid afternoon, early evening) should be enough, except when doing a lot of computer work or reading in which case putting drops in before starting and then every few hours is helpful.
Environmental factors also play a role; dry eyes are worse in the winter when it is cold and dry- patients may need more frequent drops at this time. Using a home or work humidifier in can be helpful.
Other treatments for more severe dryness include prescription drops, and treatments to prevent tears from draining away from the eye. The prescription drops (Restasis and Xiidra) reduce the inflammation associated with dryness but generally do not increase the amount of tears. The medications in these drops have to build up gradually in the tissues of the eye, so they rarely improve symptoms quickly- they may take 4-6 weeks to reach full effectivness. The most common side effect is that some patients do not find them helpful.
The tears we produce drain away from the eye through tiny tubes that connect the inner corner of the eye with the back of the nose. When we “taste” eye drops, it is because they have gone down these tubes. A treatment for dry eye involves plugging up these tubes so the tears we make stay on our eyes longer. This can be done with temporary plugs that self dissolve to see how effective the treatment might be, with more permanent plastic plugs, or by permanently sealing the tube surgically.
Which artificial tears should I use?
Picking which drops to use in the drug store can be confusing.There are now many different kinds of drops, and even confusing variations of the same brand. Common names for artificial tears are Refresh, Refresh Optive, and Systane- and they come in all of the confugurations descibed below. You have to be careful to scrutinize the label to be sure you are getting the one you want.
Generally over the counter drops (OTC) drops at the drug store are used for two purposes. One is allergies, and the other is dry eye. The allergy drops usually state their purpose, or say “gets the red out” and are generally not useful for dry eyes. The dry eye drops come in three configurations. The first is just wetting drops that usually say “lubricating” on the packaging. Second are drops that are thicker that say “long lasting” or “gel” on the packaging. The advantage of the latter is that they are thicker than the lubricating drops and therefore stay on the eye longer so require less frequent use. A disadvantage is that they sometimes blur the vision for a short time. Third are drops that are preservative free and usually state so or say “PF” on the packaging. All of the preservative free drops come in one use vials, so if your eye drops are in a bottle, they are not preservative free.
While it would seem that the preservative free drops would be the best choice, most people do not need them. Very few are sensitive to the preservatives in the usual artificial tears, but if your eyes get more and more irritated as you use tears, you probably need the preservative free version- or you may have a different eye problem that requires an examination.