II DRY EYE
I g o r P e t r i cˇ e k
WHAT IS DRY EYE? Virtually everyone has experienced some dry eye-related complaints in his/her life, in most
cases completely unaware that those complaints were actually caused by tear dysfunction. Either when driving with an open window, working on the computer, especially in an air con-
ditioned room, or having teary eyes on a cold winter morning. It is one of the most challen- ging eye disorders, because it is perhaps the most diverse of them all. At one end of the dry eye spectrum are mild, infrequent complaints and on the other, severe, debilitating, eye-threa- tening inflammation. It is virtually impossible, and highly individual, to draw the line between
dry eye conditions that are part of our everyday lives and those that must and should be treated. This fact poses the biggest problem of dry eye diagnosis and treatment, as well as the epidemiology of dry eye.
It is the general practitioner’s right, as well as their responsibility, to diagnose and treat dry eye. It is not solely the ophthalmologist’s domain, since the largest segment of the dry eye spectrum does not pose a serious threat to the eye and visual function, and remains more symptom than sign-defined. In most cases, dry eye is an age related decrease of tear protec- tion of the eye surface. Other causes of dry eye (autoimmune, neurological etc.) are far less common, although potentially more dangerous.
Therefore, general practitioners should be able not only to recognize and treat uncomplica- ted dry eye, but also to detect those dry eye-related conditions which may be potentially more
dangerous to the eye, and should be referred to the ophthalmologist.
That is the purpose of this guideline.
In order to give the best treatment, while also not overburdening the health system by over-
referral, a correct diagnosis must first be made. Using this guideline, general practitioners may
be able to correctly diagnose dry eye as the leading cause of a patient’s complaints, even without using more sophisticated tools and tests, available only to the ophthalmologist. Also, it is important for them to be able to differentiate which cases of (presumably) dry eye should be referred to the ophthalmologist, in order to either run more thorough diagnostic algo- rithms, or to modify therapy.
DEFINITIONS OF DRY EYE
There are many definitions of dry eye, depending on the criteria used. Listed here are those most relevant to the approach used in this guideline.
Dry eye is a disorder produced by the inadequate interrelation between the lacrimal film and the ocular surface epithelium, caused by quantitative and qualitative deficiencies in one or both of them (The Madrid triple classification of dry eye was created by a group of experts (Murube, Benitez del Castillo, ChenZhuo, Berta and Rolando), first published in 2003 , later it was modified and accepted by a larger group of experts in 2005 ).
Dry eye is a disorder of the tear film due to tear deficiency or excessive tear evaporation which causes damage to the interpalpebral ocular surface and is associated with symptoms of ocular discomfort. 
3. Dry eye is a disease of the ocular surface attributable to different disturbances of the natu- ral function and protective mechanism of the external eye, leading to an unstable tear film during the open eye state. 
EPIDEMIOLOGY OF DRY EYE
How prevalent is dry eye? Is it a serious, eye-threatening condition? Because of this question,
which may be answered in various ways, depending on the definition of dry eye applied, exact prevalence data for dry eye in the general population does not actually exist. Vast numbers of studies have analysed dry eye in the general population of various countries, but, since almost every study defined dry eye differently, and thus used different inclusion criteria, all the data is very difficult to compare. Nevertheless, we will list several published studies to enable rea-
ders to get a general impression of dry eye prevalence.
Jacobson et al. found that the prevalence of dry eye in the Swedish population, in the age group 55 – 72, was 15 % . A Japanese study led by Hikichi demonstrated that 17 % of scree- ned Japanese patients had dry eye symptoms . A study conducted in Copenhagen showed that the prevalence of dry eye in the age group 30 – 60 in the general population was 11 % . A study in the elderly conducted in Salisbury, Maryland and published in 1997 reported that 59 % of the screened population complained of dry eye symptoms . The Beaver Dam Study (2000) showed the figure to be 14.4 % .
THE TEAR FILM The tear film is not just water on the eye. It has a very complex structure. Its elements must interact adequately and must be present in sufficient quantity and quality to provide an opti- mal protective function to the eye surface.