Boston—Lid wiper epitheliopathy has been receiving increased attention of late, because it is highly correlated to dry eye states and helps to explain one aspect of the conundrum of lack of correlation of signs and symptoms with dry eye disease.
In fact, as Donald R. Korb, OD, explained, lid wiper epitheliopathy is frequently identified when patients complain of dry eye symptoms, even though there are no findings of clinical dry eye disease.
The lid wiper, he explained, is the aspect of the marginal conjunctiva of the upper eyelid that wipes the ocular surface during blinking, much like the windshield wiper on a car. In 1904 J. Herbert Parsons, MD, first recognized that this portion of the upper lid has a different type of epithelium-i.e., squamous epithelium-from the rest of the upper lid. This observation did not receive additional attention with the exception of two acknowledgements in the 1960s. Until recently, the potential for pathology of the lid wiper, i.e., lid wiper epitheliopathy, compromising the surface of the eyelid that comes into contact with and manages the ocular surface had not been addressed.
"No one ever looked at lid wiper epitheliopathy because staining is necessary for this observation, and for a real understanding of this pathology two stains are needed, fluorescein and rose bengal dyes," explained Dr. Korb, who is in private practice in Boston and the director of research of Ocular Research of Boston.
Dr. Korb and colleagues later broadened their research to show that lid wiper epitheliopathy occurs in the presence of all dry eye states.
"Every day humans blink between three to 15 times per minute, which adds up to a minimum of 180 times per hour or more than 4,000 times per day. To understand the etiology of lid wiper epitheliopathy, think of the consequences of passing one surface over another surface without the proper lubrication. When the inevitable irritation reaches a certain point, dry eye symptoms ensue.
The major breakthrough was the realization that 95% of all dry eye symptoms, except burning, are due to the lid wiper. Once tear film lubrication is compromised, the cells on the lid wiper are traumatized, the changes in turn are detected by staining," Dr. Korb stated.
Lid wiper epitheliopathy is frequently associated with insufficient thickness of the lipid layer of the tear film. It appears that, as the lipid layer thickness becomes compromised, the prevalence of lid wiper epitheliopathy increases, Dr. Korb pointed out.
Another factor in lid wiper epitheliopathy is inflammation. As Sir Thomas Lewis observed, trauma to any surface in the body produces an inflammatory response and one of the mediators that govern the response after trauma is histamine, which produces an inflammatory cascade and the inflammatory markers of dry eye. The inflammation in lid wiper epitheliopathy is the result of the trauma.
Dr. Korb and coworkers conducted a study that included 100 individuals equally divided into those with and without symptoms of dry eye, as determined by responses to a questionnaire. All participants also had a tear film break-up time of greater than 10 seconds, Schirmer testing results of 10 mm or more, and no fluorescein staining of the cornea. After rose bengal stain was instilled, the lid wipers were graded for staining on a scale of 0 to 3, where 0 indicated no staining and 3 severe staining.
The investigators found that in the individuals with dry eye symptoms, more than three quarters had staining of the lid wiper-most, 44%, with grade 1 staining, 22% grade 2, and 10% grade 3. Interestingly, of the asymptomatic subjects, 12% of individuals with no symptoms had staining; of those, 8% had grade 1 staining and 4% grade 2. None had grade 3 staining. The difference between the groups was significant (p < 0.0001). Lid wiper epitheliopathy was found to be six times more common in individuals with symptoms of dry eye than in those without symptoms. These findings were reported at the 2004 annual meeting of ARVO.