Article

By: Christopher E. Starr, MD

Hyperosmolarity is a well-established fundamental characteristic of dry eye disease (DED).¹

When patients have dry eye symptoms, osmolarity testing is a logical step to confirm the diagnosis, but what does it mean when the tear osmolarity test is normal in a patient with symptoms suggesting DED?

In the early days of point-of-care tear osmolarity testing, many practitioners faced with this diagnostic dilemma assumed the test was inaccurate because it went against their clinical judgment. When osmolarity testing disagreed, our early reaction was often that the machine must be wrong. We now know otherwise.

Just as tear osmolarity can help us diagnose DED, it can also help us know when to pause and look for an alternative diagnosis. My colleagues and I conducted a study exploring how osmolarity testing can help make alternate diagnoses in symptomatic patients.

Take-home message

Patient symptoms are not an effective method to diagnose dry eye as they often overlap with other pathologies. Tear osmolarity results provide clues for alternative diagnoses.

Alice T. Epitropoulos, MD, Cynthia Matossian, MD, Gregg J. Berdy, MD,
Ranjan P. Malhotra, MD, Richard Potvin, OD

● PURPOSE: To evaluate the effects of tear osmolarity on the repeatability of keratometry (K) measurements in patients presenting for cataract surgery.

● SETTING: Three clinical practices.

● DESIGN: Observational prospective nonrandomized study.

● METHODS: Subjects were prospectively recruited based on tear osmolarity (Tearlab Osmolarity System); that is, osmolarity more than 316 mOsm/L in at least 1 eye (hyperosmolar) and osmolarity less than 308 mOsm/L in both eyes (normal). The baseline K value was measured, and a second measurement was taken on the same instrument (IOLMaster) within 3 weeks of the first. Variability in average K, calculated corneal astigmatism using vector analysis, and intraocular lens (IOL) sphere power calculations were compared between groups.

● RESULTS: The hyperosmolar group (50 subjects) had a statistically significantly higher variability in the average K reading (PZ.05) than the normal group (25 subjects) and a statistically significantly higher percentage of eyes with a 1.0 diopter (D) or greater difference in the measured corneal astigmatism (PZ.02). A statistically significantly higher percentage of eyes in the hyperosmolar group had an IOL power difference of more than 0.5 D (P Z .02). No statistically significant differences were present when the subjects were grouped by self-reported dry eye.

● CONCLUSIONS: Significantly more variability in average K and anterior corneal astigmatism was observed in the hyperosmolar group, with significant resultant differences in IOL power calculations. Variability was not significantly different when subjects were grouped by self-reported dry eye. Measurement of tear osmolarity at the time of cataract surgery planning can effectively identify patients with a higher likelihood of high unexpected refractive error resulting from inaccurate keratometry.

Duane’s Foundations of Clinical Ophthalmology – Volume 2
Physiology of the Eye and Visual System
Daniel G. Dawson, Mitchell A. Watsky, Dayle H. Geroski, Henry F. Edelhauser

Please click below to view Chapter 4 detailing the cornea and sclera of the vast reference that is Duane’s Foundations of Clinical Ophthalmology.

By: Paul Karpecki, OD, Ian Benjamin Gaddie, OD, David Geffen, OD and John Rumpakis, OD, MBA

Contact lens dropout rates have not changed appreciably in nearly two decades. Although new materials and preservative-free products have helped, neither was the tipping point we hoped for in contact lens practice. What’s more, as clinicians, we now face even greater challenges than we once did. The explosion in digital device use has placed an unprecedented burden on the ocular surface, erecting yet another hurdle to comfort. If there is one thing we have learned about contact lens dropout, it is this: We are less likely than ever to overcome it using traditional strategies. It’s time to start thinking outside the box.

In our clinical experience, and in that of many of our forward-thinking colleagues, the most effective way out of what is otherwise sure to be a downward spiral is to catch as many patients as we can as they come in for their annual exams. In other words, we need to identify which patients are at risk of dropping out prior to first fittings and before refits.

In this three-part series, we will explore how osmolarity testing can be the catalyst for change that the contact lens industry has long sought. This surprisingly simple approach is both practical and profitable.

(Review of Optometry, May 15 2016)