I see this scenario often: A patient presents to the office, after being seen by three or more different eye care professionals. She has tried multiple therapies, ranging from artificial tears and topical anti-inflammatories, to punctal occlusion, nutritional supplementation and oral medications, and has experienced no significant improvement in symptoms.
Her osmolarity measures 289mOsmol/L OD and 288mOsmol/L OS; meibomian gland expression is turbid or grade 1; and there is trace inferior corneal staining. All other tests are relatively normal. Given the osmolarity reading—and considering that both eyes are within 5mOsmol/L of each other—it's more than 95% likely she doesn't have DED.
Establishing a correct diagnosis the first time would have saved this patient a lot of heartache and money. So, how do we more effectively diagnose our dry eye patients?
The Glaucoma Testing Model
You'd never consider measuring IOP alone when evaluating for glaucoma, because you’d either potentially miss a lot of normotensive cases or needlessly treat many patients with pressures above 22mm Hg who exhibit no other relevant clinical signs. In other words, while there is definitive value in an IOP measurement, the test by itself offers low specificity and sensitivity.
Likewise, if you only performed visual field testing during a glaucoma workup, you'd miss almost all of the early and some of the moderate cases of glaucoma. Visual field testing along would yield high specificity, but low sensitivity.
Thus, it’s the combination of IOP measurement, OCT evaluation, optic nerve head visualization, gonioscopy and pachymetry, combined with visual field testing that demonstrates both high specificity and sensitivity with respect to the diagnosis of glaucoma.
So, why do doctors typically try to oversimplify the diagnosis and testing when it comes to DED?
Diagnosing Mild and Moderate DED
Simplifying the DED diagnostic process starts with determining who exactly has dry eye. And, to accomplish this, you must be able to identify both mild and moderate disease, as well as more severe forms. For years, clinicians would use Schirmer testing and NaFl corneal staining to make a positive diagnosis of DED. That’s insufficient by contemporary standards.
Studies show that tests like corneal staining are reliable at identifying late-stage disease, but too often miss early, mild and even moderate disease in many cases.1 So, the key is to use a variety of tests not only to confirm the presence of DED, but also to determine its severity.
Here’s a useful reference:
Early or Mild Disease
• Validated questionnaires (e.g., DEQ-5, SPEED, etc.)
• Osmolarity testing
• Lissamine dye staining (also helpful in mild DED)
• Tear film break-up time (noninvasive versions may also assist in mild DED)
• Meibomian gland expression (also helpful in mild DED)
Severe or Advanced Disease
• Confluent, macro, coalesced or central corneal staining
• Tear meniscus height
• Schirmer tear test
• MMP-9 point-of-care testing
Note that many of the aforementioned tests identify more than one level of dry eye disease severity (e.g., meibography, osmolarity, lissamine dye, meibomian gland expression, validated questionnaires), but are listed at the levels where they excel specifically. Ideally, you should employ one or two tests per category to increase both specificity and sensitivity.
In Part 2 of this pearl, I’ll review the most effective ways to determine which type of DED your patients have.
1. Schargus M, Ivanova S, Kakkassery V, et al. Correlation of Tear Film Osmolarity and 2 Dif-ferent MMP-9 Tests With Common Dry Eye Tests in a Cohort of Non-Dry Eye Patients. Cor-nea. 2015 Jul;34(7):739-44.