Would you like to offer an objective and quantitative test for diagnosis and management of Dry Eye Disease (DED) to your patients? We’ve got your number.
Osmolarity has long been recognized as the gold-standard marker for diagnosing DED. However, until now, there has never been a way to use this marker in clinical practice. As the TearLab™ Osmolarity System expands across Europe and North America we are learning more and more about DED (Dry Eye Disease) and how to manage this patient population more effectively.
Having had the opportunity to test hundreds of patients personally and speak to most TearLab users, this advanced nano-technology provides us with better information and truly revolutionizes the management of DED patients. TearLab provides a paradigm change in the way we look at DED, and it is my hope that the following article provides the educational information that is needed to excite the industry about this technology. Its what we’ve been waiting for!
Understanding the Technology
TearLab measures Osmolarity. Simply and Accurately.
FDA clearance received in the summer of 2009 showed that TearLab’s lab-on-a-chip technology measured osmolarity at a 95% correlation to a laboratory osmometer (Wescor 5520). More importantly, the TearLab requires only 50 nL of tear fluid – a volume hundreds of times smaller than those used in standard osmometers, and to put it in perspective, it is about the same size of the period at the end of this sentence. TearLab delivers a simple, fast and accurate way to measure tear osmolarity at the point-of-care; Technicians can perform the test in seconds with even less effort or stress than tonometry or pachymetry.
Why is Osmolarity so important?
Osmolarity is so significant as a global marker for Dry Eye Disease, it has been added to the definition. It is the single most accurate way to determine DED. This has been documented in thousands of patients over the last sixty years in peer-reviewed literature, but until now, there has been no way to measure osmolarity in clinical practice. Osmolarity has a positive predictive value of disease severity in the 90% range where all other commonly used dry eye diagnostic procedures (Schirmer’s, TBUT, Corneal Staining, OSDI) fall in the 30% range, and we know how our patients feel about these tests. Osmolarity has a huge advantage over alternate dry eye measurements because it provides an objective reference number that is so sensitive, it can help diagnose mild and moderate dry eye, an area where most of our current tests data is more similar to a random number generator. (See, http://www.tearlab.com/products/doctors/articles.htm, )
What’s your number?
It is imperative to test both eyes to determine true status of the patient’s osmolarity simply because DED is bilateral but not symmetric.
A non-DED patient will typically have normal levels of Osmolarity (less than 308 mOsms/L) and will be remarkably consistent in both of their eyes. Our research shows that levels of osmolarity in “normals” only vary by 5-7 mOsms/L during the day both intra-eye and inter-eye. Always remember DED is a bilateral disease but not symmetrical. Be very suspicious if the patient presents with a delta of more than 15 mOsms/L. DED in this case is similar to glaucoma where patients may have variable IOPs and normals typically have less diurnal swings than those with glaucoma.
Mild to Moderate DED patients usually will have at least one eye over the 308 mOsms/L level. We have found that at the onset of the disease, the body’s compensatory mechanisms are hard at work trying to adjust. As the severity of the disease increases, so too does the osmolarity. The variability between eyes can also increase due to compensation.
The compensatory mechanisms in play may result in a patient’s first eye measurement of 300 mOsms/L while their second eye reaches 325 mOsms/L or even higher. As we learn more about dry eye disease, we find that high osmolarity causes an unstable tear film to form, which is why it is critical to take the higher measurement of the two eyes when making a diagnosis. The more unstable the tear film, the higher the osmolarity. Does the osmolarity cause the instability or vice versa?
We now know that DED is progressive, and one of the hallmark signs of this progression is the potential variability of osmolarity in readings between the 2 eyes over time. We are also learning that compensatory mechanisms work transiently and differently in each eye. When patients are treated properly, their osmolarity becomes lower and stable over time, much the same way we observe changes in blood pressure or IOP during treatment.
Some patients present with dry eye like symptoms but show consistently low osmolarity readings. What we have found is that since dry eye disease is multifactorial in nature, many clinicians attribute non-specific ocular surface disease, by default, to dry eye. However, if the patient’s osmolarity is consistently low in both eyes, their symptoms are most likely not caused by dry eye disease, but by an undetected allergy, infection, or inflammation around the nerve. With a consistently low osmolarity, you can be confident that their lacrimal and meibomian glands are doing their job.
Remember, it is up to you the clinician to determine their diagnosis utilizing your skills and all the other tests at your disposal. TearLab is extremely accurate but it shouldn’t replace your skills in differential diagnosis.
You make the diagnosis but TearLab provides the support
Understanding the disease makes this diagnosis much simpler; and with Osmolarity being 90% predictive of DED, the TearLab test will give you confidence in the diagnosis. You still need to use your clinical judgement and some of the other diagnostic tools to identify inconsistencies or evaluate results that fall within that rare 10% range. It may be necessary to take a few readings over time to get a clear picture. This is not unlike re-checking IOP findings or doing ancillary tests to confirm the diagnosis of glaucoma.
The Dry Eye Severity scale enables a more accurate categorization of where the patient is in relation to the progression of the disease. Using this will help provide a starting point for developing the appropriate treatment regimen.
TREATING Osmolarity
A high osmolarity reading has the potential of causing the loss of
the ability of the tear film to maintain its compositional and physiological integrity, resulting in an unstable tear film between blinks. Eventually, these factors lead to a desiccated, inflamed ocular surface with compromised visual acuity and symptoms of ocular irritation and pain
How do I use TearLab in my practice?
While having a “number” is important in understanding disease classifications and effectiveness of treatment regimen, it is very powerful for patient education. Patients understand a number. It’s no different than having a number for their blood-pressure, blood-sugar or cholesterol levels.
The number is also critical in being able to demonstrate treatment effectiveness when they “don’t feel any better.” Many doctors that use TearLab find that it is a wonderful tool for improving compliance, “Mrs. Jones, your osmolarity reading is 338 mOsms/L. I want you to use these drops, punctual plugs or supplements, and I’m going to evaluate you again in a few weeks and we’ll see what your number is next time.”
Patients will understand and appreciate the level of professionalism that you are demonstrating in dealing with what is, to them, a very significant lifestyle issue. Statistics show that approximately 30% of patients presenting to your practice have symptoms or complaints of DED. There can be many more that don’t know they have DED who assume everyone has the symptoms they experience. Consider the 50% of contact lens wearers that drop out because of contact lens induced dry eye. You now have a tool that can make a real difference in a new patient contact lens fitting, as well as monitoring current wearers. Studies have begun to show that certain lenses and proper care cause less of an increase in osmolarity (and therefore better biocompatibility and comfort) for dry eye patients.
There are multiple other aspects to using TearLab in building a dry eye practice. As you all know, the most significant negative outcome from laser surgery is dry eye. Measuring tear osmolarity will soon become standard-of-care and allow detection of DED patients pre-op and help guide treatment before surgery. It is very important to ensure the health of the tear film before surgery to promote optimal wound healing and give patients the best chance for a high quality refractive outcome.
TearLab can also be used in management of cataract patients, many of whom have dry eye. One of the most important elements in obtaining rapid quality improvement of vision post cataract surgery happens to be the quality of tear film. A poor quality lipid layer or insufficient aqueous production leads to blurry vision after only a few seconds post-blink. So while these patients can get by on a Snellen chart, their ability to drive a car at night, react quickly to oncoming challenges, or read for long periods of time can be quite compromised. A healthy tear film tends to improve all of these areas of vision. This is particularly important in cases where patients are paying a premium IOL fee and carry high expectations into the surgery.
Conclusion
In just the first year of the availability of the TearLab, we have learned an extraordinary amount about dry eye disease that was not known before. In summary:
1. TearLab measures osmolarity extremely accurately.
2. An osmolarity measurement is the highest measurement between left and right eye, because DED is bilateral but not symmetric.
3. Osmolarity and dry eye disease are 90% correlated. Osmolarity has been recognized as the best single test for dry eye disease.
4. The diagnosis of high osmolarity should be addressed as it may compromise quality of vision, cause chronic inflammation and potentially damage the ocular surface.
Being able to accurately assess and manage DED could be one of the most effective tools in building both your reputation and patient base. Most reliable estimates state we have 40 to 50 million Dry Eye patients in the US. The average practitioner has more than enough patients to build a DED specialty just from their current patient base. We find that the TearLab makes managing dry eye patients rewarding to both patient and practice.
Q&A
Q. Why do I have to test both eyes?
A. DED is a bilateral disease but often asymmetric and both eyes should always be tested. The higher of the two readings or the difference between the two eyes is an indicator of the severity.
Q. Does Osmolarity determine what kind of dry eye disease a person has?
A. The vast majority of DED is caused by lid disease/Meibomian Gland Disease but osmolarity helps the clinician determine the severity and assists in developing an appropriate treatment plan.
Q. Does Osmolarity change throughout the day?
A. Osomolarity in non-DED patients tends to be very stable (5-7 mOsmol/L) throughout the day while those suffering from DED may have significant differences, sometimes upwards of 15-25 mOsmols/L during the day.
Q. How will TearLab provide better care for my DED patients?
A. Having an quick accurate objective test to discuss with the patient shows you are using the latest technology and want to provide a high level of care. Having a “number” helps the patient understand their condition.
Q. Is it time consuming and will it affect my work flow?
A. TearLab is designed for technicians to perform the procedure and allow the clinician to use the information to diagnose and treat the disease. A typical measurement requires less than 15 seconds of time and is easy for the technician and for the patient.
