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The prevalence of dry eye (KCS) in the veterinary ICU | VETgirl Veterinary Continuing Education Podcasts

Are you doing Schirmer tear tests to test for the prevalence of dry eye (KCS) in your veterinary ICU?

We all know about “dry eye,” or keratoconjunctivitis sicca (what we’ll call KCS from now on), in our patients, right? It’s an immune-mediated disease that destroys the lacrimal gland, leading to decreased tear production. There are some other causes of decreased tear production, including things like endocrine diseases, medications, toxicities (e.g., like acetaminophen), anesthesia, neurologic problems, and so on. But did you know that in critically ill human patients, decreased tear production is also common? In critically ill humans, contributing causes towards KCS include inadequate eyelid closure, sedation or anesthesia, renal disease, immune disease and increasing age.

Well, Chandler et al out of the Animal Medical Center in New York wanted to see if the same is true for critically ill veterinary patients, so they looked at 30 dogs hospitalized in the ICU and compared them to 30 healthy control dogs. They performed Schirmer tear tests (STT) and had an ophthalmologist perform ocular exams on all of the patients.

In this study, the ICU group was significantly older than the control group. In the control group, the mean tear production was 24.5 mm/min, while in the ICU group, the mean tear production was 13.2 mm/min. Three of the 30 ICU patients had corneal ulcers. In the patient group, diseases included kidney disease (6/30), cardiac disease/heart failure (5/30), gastrointestinal disease (4/30), neurologic disease (4/30), and 2/30 each of metabolic disease, neoplasia, pneumonia and hematologic abnormalities. An extrahepatic portosystemic shunt, trauma and hypertrophic ostedystrophy were represented by one patient each. Patients with kidney and cardiac disease were overrepresented in the patient population, and patients in both groups had significantly lower tear production than controls, although the numbers were small.

So, what can we take away from VETgirl podcast?

This study documents significantly lower tear production in canine ICU patients. The cause is probably multifactorial, with underlying disease playing a major role. Since patients may have decreased tear production without obvious abnormalities of the eye and because ocular lubrication is easy, the authors recommend artificial tear gel instillation in all canine ICU patients (ideally every 2-4 hours). It remains to be seen if the same results are true in feline patients, but it’s worth studying in the future!

Overall, this was a great study despite its small patient population. One concern about the study was that the timing of the Schirmer tear test wasn’t standardized, which may have biased the results. Also, because of the small sample size, most diseases were not well represented, so it remains to be seen if specific diseases (such as renal or cardiac disease) are truly more frequently associated with lower tear production. That said, still… some great clinical vignettes. We now know that canine ICU patients are more likely to have low tear production compared to healthy dogs. For your critically ill patients, consider ocular lubrication for these patients! As VETgirl herself has dry eye, I can tell you painful and irritating. Lube for all!

References:
1. Chandler JA, van der Woerdt A, Prittie JE et al. Preliminary evaluation of tear production in dogs hospitalized in an intensive care unit. J Vet Emerg Crit Care 2013;23(3):274-179.

Abbreviations:
KCS: keratoconjunctivitis sicca
STT: Schirmer tear test

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