Dryness of the eyes, or Dry Eye Disease (DED) is an extremely common problem, which when persistent can be very debilitating, affecting productivity and sometimes even causing depression.
People who suffer with dry eyes might suffer from any or all of the following symptoms:
The bulk of our tears are produced by a gland called the lacrimal gland which is situated above the eye. Tears also consist of several other components, which are vital to a healthy “tear film”. In a nutshell, the tear film consists of 3 main layers (Figure 1):
1. An inner mucin layer, which helps tears to spread over the eye;
2. A middle thick watery aqueous layer produced by the lacrimal gland;
3. An outermost oily lipid layer produced by glands in the eyelid, which slows down the evaporation of tears.
With each blink, tears are spread over the surface of the eye, helping to replenish the three layers in the tear film. In addition to these three layers, there are numerous other components in tears which help to ward off infection and promote healing.
Defects in each of the layers can contribute towards DED. For some people, the main problem is not producing enough tears by the lacrimal gland. This is called “aqueous-deficienct” DED. For others, the problem is with the outermost lipid layer, meaning that tears evaporate too quickly: “evaporative” DED. For these patients, symptoms get worse whilst doing activities like driving, reading or watching TV (when we blink less often, allowing tears to evaporate). Many patients will have a combination of both of the above problems “mixed” DED.
We also now know that inflammation plays a significant role in DED, and some patients will require medicated drops prescribed by a cornea specialist, to target the inflammation. Blepharitis (inflammation of the eyelids) is also a major player in DED. (More about blepharitis in future posts!)
Other factors affect dry eye disease, and may be internal (such as hormonal factors, certain skin types or not blinking fully or often enough), or external (such as contact lens use, eye surgery and medications). In short, DED is extremely complex, and there is now a wealth of evidence to support this.
Effectively treating DED relies upon a very thorough assessment in order to identify which factor/s are contributing to the problem, and then focusing treatment on those specific problems. Unfortunately, there is no “one-size-fits-all” treatment. Some patients with mild DED may find that using “over the counter” artificial tears is enough to keep on top of things. If so, that's great! However more persistent DED warrants a full history, examination and targeted treatment, in order to crack down on the root cause and get on top of symptoms in the long-term.