• Conjunctiva
• Cornea
• Drugs
• Tears
• Lacrimal gland

We have all heard the same recurring complaint from our patients: ‘Doctor, I have to tell you something: my eyes are itching and burning. I am feeling like there is some sand in them’. Usually, when you ask this patient if this is something new, he will say: ‘no, I have been like this for many years, and I have consulted many of your colleagues; but no one has been capable of curing me properly!’ Now that your honour is at stake, you have no choice but to do better for this dry eye patient, than the last ophthalmologist he has consulted did. If not, you will suffer the same fate as your unfortunate colleagues have before you: he will leave you for someone else... What he expects from you is something new, up to date and perhaps out of the ordinary, in order to alleviate the dry eye symptoms he has been experiencing for years. He probably has already tried most of the common tears substitutes available in the market (and read everything there is to know about it on the web). Nevertheless, tears substitutes remain the first line of defence against dry eye; and the good thing is that they can be used regardless of the causative mechanism (aqueous deficiency or excessive evaporative loss). Various viscosity tears substitutes are available, from standard hypotonic artificial tears, that will temporarily increase the water content, to synthetic gels, efficient in mild and moderate dry eyes; but with poor results in severe cases.

It is important to remember that a normal tear film is isotonic. When dry eye occurs, it becomes hypertonic, causing an osmotic stress to the underlying ocular surface. This stress results in a water flow from inside the cells towards the tear film, resulting in alteration of the intracellular …