The core mechanism of DED is related to tear instability, hyperosmolarity, ocular surface inflammation, and ocular damage. Tried-and-true clinical diagnostic measures for DED include corneal staining, Schirmer's test, and tear break-up time (TBUT).[2] All of these clinical measures can increase with DED severity, but difficulty comes with grading severity as well as tailoring therapy.
The Dry Eye Workshop in 2007[3] concluded that dry eye is associated with increased tear osmolarity, and this factor has been found to be the single best marker for DED.[4] This helped pave the way for in-office tear film osmolarity analysis through devices such as the TearLab Osmolarity System. Conclusions from the Dry Eye Workshop II[5] were presented at this year's Association for Research in Vision and Ophthalmology (ARVO) meeting, and there has been a shift from focusing on DED symptoms to understanding the underlying condition.
In line with this shift, there have been advances that allow for the detection of tear film biomarkers, such as matrix metallopeptidase-9 (MMP-9), a well-known biomarker consistent with severe, late-stage inflammation. The difficulty comes when clinically differentiating between evaporative DED, commonly associated with Meibomian gland dysfunction/tear lipid abnormalities, versus aqueous-deficient DED, associated with increased inflammatory biomarkers. In some cases, it can be a mixed evaporative and aqueous-deficient picture. Currently available DED testing allows for either osmolarity testing (TearLab Osmolarity System) or MMP-9 rapid testing (InflammaDry®, [Quidel Corporation, San Diego, California]), but there is no device available that allows for simultaneous testing.
New in-office diagnostic testing may now allow for a quicker and more accurate diagnosis of dry eye while also aiding in tailoring the patient's treatment.
At this year's American Society of Cataract and Refractive Surgery meeting, Eric Donnenfeld, MD,[6] and Edward Holland, MD,[7] discussed TearLab's newest platform, TearLab Discovery, which has the potential to revolutionize the diagnosis and treatment of DED.
In less than 2 minutes and with a 100-nL tear sample, this platform provides results not only for tear film osmolarity but also for two additional inflammatory tear film markers, interleukin-1 receptor antagonist (IL-1RA) and MMP-9. IL-1RA is a T-cell-mediated inflammatory marker produced in proportion to active inflammation consistent with aqueous-deficient dry eye. TearLab Discovery uses highly sensitive fluorescent nanoparticle enzyme-linked immunosorbent assay (ELISA) to detect tear samples for MMP-9 and IL-1RA.
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