Abstract
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.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.