Get ready to hear a lot more about homeostasis. It’s a key concept that has just been added to the definition of dry eye by the Tear Film and Ocular Surface Society (TFOS). “That was chosen to reflect the myriad of potential changes that can occur to the tear film and ocular surface” that might lead to “imbalance in the system,” said Jennifer Craig, PhD, MSc, at the ARVO meeting earlier this month.
You, dear reader, will be called upon to restore that fragile balance.
At ARVO, TFOS previewed its forthcoming Dry Eye Workshop II (DEWS II) report. The mammoth volume (400-500 pages) will be published July 1st. The omnibus DEWS II is the culmination of an ambitious collaboration by 150 people in 23 countries, writing 10 separate reports.
The 90-minute ARVO session could only give highlights of such an all-encompassing work. Surely all 10 reports will be analyzed extensively, but Dr. Craig’s talk on definitions is a good place to start, as it will be foundational to the entirety of DEWS II.
First, let’s look at the 2007 definition from the original DEWS report:
Dry eye is a multifactorial disease of the tears and ocular surface that results in symptoms of discomfort, visual disturbance, and tear film instability with potential damage to the ocular surface. It is accompanied by increased osmolarity of the tear film and inflammation of the ocular surface.
And here’s the new 2017 model:
Dry eye is a multifactorial disease of the ocular surface characterized by a loss of homeostasis of the tear film, and accompanied by ocular symptoms, in which tear film instability and hyperosmolarity, ocular surface inflammation and damage, and neurosensory abnormalities play etiological roles.
What changed? In addition to the homeostasis mention, “ocular symptoms remain still important but you’ll notice it is more general this time,” Dr. Craig said, as this “accommodates the differences in symptom reporting across the world.”
For greater specificity—i.e., to help differentiate dry eye from other ocular surface diseases—the committee added a mention of etiology but stopped short of connecting causes with effects. “We have a range of the key etiological factors that are important uniquely in dry eye,” she said, but the report “made sure to mention etiological roles” so they would not “be misrepresented as diagnostic criteria.”
A new diagnostic algorithm included in DEWS II will help doctors follow these complex pathways a bit better. Dr. Craig summarized the impact of the definition and classification report in DEWS II as follows:
• It helps differentiate between dry eye and its mimickers.
• It recognizes that some patients experience signs without symptoms while others have just the opposite.
• It stresses that aqueous-deficient and evaporative dry eye aren’t mutually exclusive. Be aware of mixed cases and tailor your therapy to suit.TFOS gave itself a Herculean task in seeking to define the totality of dry eye, from pathophysiology to presentation to treatment targets, in a single sentence. Here, too, balance is the watchword: any more details would have undermined its universal appeal.