It is clear that the previously underappreciated condition of dry eye disease should now be regarded as a serious public health problem that is worthy of diagnosis and effective treatment.
Considerable progress has been made in the last 15 years regarding our knowledge on the epidemiology of dry eye disease. As we describe in this article, dry eye disease is a major and increasing healthcare problem due to its prevalence, and impact on patients' quality of life, healthcare resources and the economy. It is clear that this previously underappreciated condition should now be regarded as a serious public health problem that is worthy of diagnosis and effective treatment.
Definition of dry eye disease
It has been discovered that dry eye disease is caused by conditions that increase evaporation of the tear film or decrease tear production. The resulting increase in tear film osmolarity (hyperosmolarity) leads to ocular surface inflammation, damage, and symptoms such as dryness, burning or stinging, ocular grittiness, foreign body sensation, blurred or fluctuating vision, watery eyes, and photophobia.
"... a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface."
Problems with establishing prevalence
Epidemiological studies show wide differences in prevalence. Estimating the prevalence of dry eye disease is problematic because there is no consensus on diagnostic criteria. Another reason for the variation in prevalence estimates may be a true heterogeneity in dry eye prevalence in different populations.
A review of several large studies, conducted by the Epidemiology Subcommittee of the 2007 DEWS, showed that the prevalence of dry eye ranges between 5% and 30% in people aged >50 years.1 Considering the different definitions used in these studies, the DEWS group concluded that the true prevalence of moderate-to-severe dry eye lies somewhere close to the lower end of the range, whereas inclusion of mild or episodic cases would bring the estimate closer to the higher estimates reported.
A further difficulty in establishing the extent of dry eye disease is the fact that it is an underdiagnosed condition. Many patients mistakenly attribute dry eye symptoms to other causes, such as "getting older", and assume the symptoms are simply "something they have to live with." As a result, many patients tend to endure the condition or to self-treat with over-the-counter products, without consulting a physician or obtaining a definitive diagnosis. Indeed, the results of the 2005 Gallup Survey of Dry Eye Sufferers suggests that one in four people with dry eye do not consult a health care professional about their condition.2