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Diagnostic technology diminishes role of symptoms in dry eye
At-risk patients can be identified and treated earlier in the disease process.
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In the past 10 years, we have seen a massive change in our understanding of ocular surface disease as well as the technology we use to assist in its diagnosis and management. The vast majority of tests now give us information about aspects of tear quality, quantity and interaction with adjoining tissues that were previously immeasurable in a standard clinic setting. Items such as osmolarity, interferometry and assays for pro-inflammatory cytokines were the stuff of laboratories and research institutions but are now available for mainstream clinical use.
While no one single test is a standalone criteria for diagnosis and management, access to these objective markers is gradually changing the way we diagnose and manage dry eye disease, much to the extent that optical coherence tomography and GDx (Carl Zeiss Meditec, Dublin, Calif.) changed our ability to diagnose glaucoma at a much earlier stage.
In my own clinical setting, we rely on these technologies to assist in diagnosis and management much more than patient symptoms, which, in the context of our historical approach to dry eye, is quite a break from the norm.
Scott G.
Hauswirth
It is common now in our office to hear conversations with patients such as this: “You may feel normal at present, but your risk for progressive dry eye disease is quite high,” or “Yes, you may still be uncomfortable, but the variability in your osmolarity has decreased, and the measurements are more symmetrical between the two eyes, so we are making progress,” or “Your lipid layer has increased by 40%, which is astounding, however, it is still below the threshold at which we would expect your symptoms to be alleviated.”
This is a much different dialogue than what took place in the exam lane 10 years ago. The proliferation of evidence-based testing has pushed the conversation into discussions about specific dry eye markers instead of focusing solely on symptoms.
Earlier diagnosis important
The driving force to disempower symptoms as the critical factor is to identify patients at an earlier disease state. Patients’ symptoms are variable, increasingly so as severity increases – many of the most severe patients are miserable, but another percentage feel perfectly fine. However, this variability appears no matter what test is performed in a dry eye patient; variability within our readings is part of the norm.
Corneal and conjunctival staining may wax and wane, osmolarity numbers go up and down, and even lipid layer thickness is variable, especially in patients who are aggressive blinkers or who rub their eyes to compensate for their irritation, consciously or unconsciously.
It is crucial for the clinician to understand that this variability is the hallmark of the dry eye patient; the body is using every means it can to compensate for and reduce the likelihood of tissue damage and to restore a healthier surface.
Symptoms play an important role in alerting our conscious mind to an adverse stimulus; however, when we begin to see recurrent symptoms, it is often evident that tissue damage has already been occurring. This is especially true of the older segment of patients, who likely have several years of progressive tissue damage to help explain either chronic symptoms or the complete lack of them. The process of inflammation and disruption of the neuronal feedback system helps explain this phenomenon.
Another disadvantage in relying on symptoms as our primary indicator is that there are plenty of other pathologies relating to the ocular surface that will not change significantly if attributed to dry eye. Pingueculae and pterygia, anterior basement membrane dystrophy, conjunctivochalasis, lagophthalmos and incomplete blink are but a few of the common conditions that may give the patient a reasonably similar set of symptoms. Complicating the picture, many of those conditions also arise as part of ocular surface disease as well as contribute toward progression in some way. Further, many of them may not respond well to dry eye therapy alone and need to be addressed as separate entities.
Variety of available tests
So, which of these diagnostic technologies is most beneficial to clinical practice? As of yet, the answer to this question is difficult to determine, as all of the tests provide information we did not have access to previously, and they each tell us something different, yet are all uniquely important and correlated with disease state.
Tear film osmolarity is defined as a core mechanism of dry eye disease and is correlated with disease severity and risk for progression, assuming that osmolarity and inflammation truly are the driving forces behind progressive ocular surface disease. We know decreased lipid layer thickness contributes significantly to tear film instability, creating decreased tear break-up time and causing fluctuations in vision as well as exposure of the tissues of the ocular surface. However, a decrease in tear stability also may cause an increase in tear film osmolarity and usually creates increased variability in osmolarity readings.
The newest test to hit the market, InflammaDry (RPS), may tell us who is at risk for progressing more rapidly, requiring more aggressive anti-inflammatory treatment to protect tissues from immune-mediated damage, thought to be another core mechanism in the ocular surface disease process.
The bottom line is that at this point, we have reached a critical stage where we can now treat those patients who are at risk for dry eye disease as well as identify them earlier in the disease process. I view this as a significant advantage to our previous methods of diagnosis and treatment. If we have an opportunity to treat a disease earlier, when it has only minimally disrupted our normal physiology and is easier to treat and normalize, how can we opt instead to see that patient back in 10 to 20 years when they may have progressed to having irreversible tissue damage and are much more difficult to treat?
Incorporation of these technologies into our mindset and our way of thinking about dry eye disease can be challenging. With the advances in technology and the increased investment into dry eye disease, we can expect the next decade to give us the opportunity to learn more about our patients’ disease than we could previously, as well as allow us to be proactive and actually prevent its occurrence.