Erich Knop1 , Nadja Knop1
1 Ocular Surface Center Berlin (OSCB), Univ Charite Berlin, Dept Cell & Neurobiol, Berlin, Germany

Disclosure Block:Erich Knop, None; Nadja Knop, None

Purpose:Dry Eye Disease (DED) is a complex alteration of the functional anatomy of the ocular surface that is still insufficiently understood and current concepts are often oversimplified.

Methods:A pubmed based review of the literature on DED was performed and pathogenetic mechanisms identified. These were arranged in a patho-physiologic hierarchy that reflects the causative relations of events in DED and also reflects clinical findings but is independent of assumed clinical importance.

Results:Structural and functional alterations of the integrity of the ocular surface and the secretory elements as aqueous lacrimal glands (LG dysfunction, LGD) and the Meibomian glands (MG dysfunction, MGD) together with the integrity of the eyelids and the regular blinking mechanism (termed lid and blinking dysfunction, LBD) are defined as basic primary causative factors for DED. They result in tear film deficiency and ocular surface tissue damage that are both defined as primary pathologies. Tear film deficiency as well as ocular surface damage are both governed by secondary pathogenetic factors. In tear film deficiency there are e.g. tear instability, dry spots, friction and hyperosmolarity. Surface damage is governed by e.g. epithelial activation, inflammation and impaired tissue differentiation. The primary causative factors are influenced by underlying regulatory systems such as the neural innervation, endocrine and immune systems. Overlying influence factors act either on the differentiation of the tissues as internal factors and on their secretions as external factors. The nervous system regulates function but also pain sensation that is modulated by higher order mechanisms and can lead to chronic pain syndromes. In contrast to present over-simplified models we have identified several, different, interacting vicious circles or disease aggravation and perpetuation.

Conclusions:This new concept on the pathophysiology DED incorporates long established as well as new mechanisms in the pathophysiological order. It is complex but not complicated - intuitively understandable and suitable to assist basic scientist and practitioner alike. An educational computerized animation is made to promote the understanding of dry eye disease.

Layman Abstract (optional): Provide a 50-200 word description of your work that non-scientists can understand. Describe the big picture and the implications of your findings, not the study itself and the associated details.:Dry Eye Disease (DED) is a widespread pathologic condition of the ocular surface characterised by irritation, unstable visual acuity and pain - is is the most frequent diagnosis in opthalmological practice but can often only insufficiently be treated. DED reduces work productivity and the quality of life and it is a financial burden to the social system. Since the rate of DED increases with advancing age it will be of growinig importance in an aging society.
The disease is complex and the enormous amount of new data in research and clinics on ocular surface and DED makes the understanding of this condition more and more multifaceted, complicated and increasingly unintelligible to many people. Therefore we have developed a completely new way to see and view the normal ocular surface and its pathological changes in DED. This is a holistic way that allows to see the full picture at first glance like a landscape from above and it is thereby intuitively understandable.
This new concept on the basics and course of Dry Eye Disease incorporates long established as well as new findings in a natural pathophysiological order and can thereby instruct the clinical practitioner to identify and treat the specific primary problem/s in his individual patient more effectively.An educational computerized animation is made to promote the understanding of dry eye disease.