Part 1 of this pearl outlined a variety of diagnostic tests you can perform synergistically in order to determine and grade a patient’s DED severity. Part 2 will review how you can most effectively determine which type of DED he or she is suffering from.
Once you confirm that a patient has DED and have graded its severity, you must determine which type of dry eye he or she has: aqueous deficient, evaporative or mixed. And, this is where more advanced testing, as outlined in Part 1, is tremendously helpful.
As an example—although osmolarity testing has been shown to be the most accurate test for the diagnosis of dry eye, it will not help you to differentiate aqueous deficient DED from evaporative DED.1 Moreover, meibography in and of itself is more specific to evaluating for evaporative dry eye than aqueous-deficient dry eye. And to make matters more complicated, keep in mind that it's also possible to have exhibit elements of both disease forms concomitantly.
Once the diagnosis of DED has been established based on a questionnaire, osmolarity testing, non-invasive tear film break-up testing and/or staining, the next step is to determine the type of disease. The basics of differentiating DED type will depend on findings from each of these tests:
For Evaporative Dry Eye
- Meibomian gland expression
- Absent lipid pattern
- Evaluation of the lid margins for drop out, plugging or vascularity
For Aqueous Deficient Dry Eye
- Tear meniscus height less than 0.2mm
Finally, there are other tests like partial blink analysis (e.g., LipiView and IPEDA) that not only aid in DED diagnosis, but also can help clinicians monitor for the potential of disease progression. (This is similar to hysteresis for glaucoma, which can predict which patients are most likely to progress in visual field loss.2)
As an aside, if you want more information on more effectively differentiating DED types, the TFOS DEWS II report provides outstanding detail.1
1. Wolffsohn JS, Arita R, Chalmers R, et al. TFOS DEWS II Diagnostic Methodology report. Ocul Surf. 2017 Jul;15(3):539-74.
2. Medeiros FA, Meira-Freitas D, Lisboa R, et al. Corneal hysteresis as a risk factor for glaucoma progression: a prospective longitudinal study. Ophthalmology. 2013 Aug;120(8):1533-40.