PECAA Practice Pearl: Think of Dry Eye Disease Like You Would Glaucoma
By: Paul M. Karpecki, OD, FAAO
Clinical Director – PECAA
A key to successful dry eye disease management is getting the right diagnosis. Today you not only have to determine if it’s dry eye disease (DED) but also the type of DED.
I see this scenario often: A patient presents to the office having seen 3 or more doctors and has tried over a dozen therapies ranging form anti-inflammatory, obstruction treatments, nutritional supplement, artificial tears, oral medications etc. with no significant improvement in their symptoms. Osmolarity measures 289 OD and 288 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 of between 280 and 295 and both eyes within 5 mOsmol/L of each other, it’s more than 95% likely they don’t have dry eye disease. Having the right diagnosis initially would have saved the patients a lot of heartache and money. So how do we get more specific with our diagnosis?
Think like you would in managing glaucoma
You’d never consider measuring IOP alone for a diagnosis of glaucoma because you’d miss a lot cases that were glaucoma with normal pressures and treat many patients with pressures above 22mHg that would never develop glaucoma. In other words you’d have a low specificity and sensitivity for diagnosis, yet there is value in the test, when combined with other measurements. Likewise if you just added Visual Field testing you’d miss almost all of the mild or early cases of glaucoma (high specificity but very low sensitivity). In fact it’s the OCT, optic nerve head visualization, hysteresis, gonioscopy, pachymetry, tonometry combined with visual field testing that aids in the diagnosis or better said, the specificity and sensitivity for the disease. So why do doctors typically try to simplify the diagnosis and testing when it comes to DED?
Diagnosing mild and moderate dry eye disease
Making things simple in DED diagnosis starts with determining who has DED. That is to identify the mild and moderate in addition to severe forms of the disease. Traditionally doctors would use Schirmer testing and NaFl corneal staining to make a positive diagnosis of DED. Well that’s about the same as using visual field testing to determine who has glaucoma. Studies show that tests like corneal staining are good at identifying late disease but miss early, mild and even moderate disease in most cases. So the key is to increase sensitivity and specificity by using multiple tests, like in glaucoma. In addition to the correct diagnosis, it will help identify early or mild cases of DED. Here’s how the tests break-out:
Early or mild DED
• Validated questionnaires (e.g. DEQ-5, SPEED etc.)
• Osmolarity testing (most specific for mild DED (1) )
Moderate disease tests
• Lissamine dye staining (also helpful in mild DED)
• Tearfilm break-up time (non invasive versions may also assist in mild DED)
• Meibomian gland expression (also helpful in mild DED)
Severe or advanced disease
• Corneal staining that is confluent, macro, coalesced or central
• Tear meniscus height
• Schirmer tear test
• MMP-9 POC testing (2)
Note that many of the tests above identify more than one level of dry eye disease (e.g. meibography, osmolarity, lissamine dye, MG expression, validated questionnaires) but are listed where they excel uniquely. Ideally you should have 1 or 2 tests in each category to increase sensitivity and specificity.
Distinguishing between the Types of DED
Once you know you have DED as opposed to a disease that mimics dry eye symptoms, the next determination is the type: aqueous deficient, evaporative or mixed.
Here is where more specific tests from above help. As an example, although osmolarity testing has been shown to be the most accurate test for the diagnosis of DED 1, including mild DED, it will not specifically differentiate aqueous deficient DED from evaporative DED. It simply tells you about the degree of lack of homeostasis of the tear film (imbalance of solutes to solution). Whereas tests like meibomian gland expression and meibography are more specific to evaporative dry eye. Keep in mind that it’s also possible to have both forms— or mixed DED.
Finally there are even tests like partial blink analysis (e.g. LipiView or IPEDA) that indicate the likely acceleration/progression of the disease, in addition to diagnosis. This is similar to hysteresis for glaucoma, which not only helps with the diagnosis but predicts those most likely to progress. Indeed it’s time to start thinking of DED diagnosis like glaucoma diagnosis. To increase the use of testing, but in an efficient manner, to increase sensitivity, specificity and even typing of DED.
- Akpek EK, Mathews P, Hahn S, et al. Ocular and systemic morbidity in a longitudinal co-hort of Sjögren’s syndrome. Ophthalmology. 2015 Jan;122(1):56-61.
- Schargus M, Svetlana I, Kakkassery V. et al. Correlation of Tear Film Osmolarity and 2 Differ-ent MMP-9 Tests With Common Dry Eye Tests in a Cohort of Non–Dry Eye Patients. Cornea Volume 0, Number 0, Month 2015