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    How tear osmolarity affects lens wear

    Diagnosing, treating osmolarity efficiently may lead to less CL dropout

    We have heard it a million times: Discomfort is the number one reason that patients drop out of their contact lenses (CL).1 Yet, when we sit behind the slit lamp explaining ocular surface findings that will lead to discomfort, the patient refuses to take the warning seriously.

    A challenge for many of us is that CL patients perpetuate their wearing behaviors based on the perception of past success, or lack of obvious consequence. These patients believe if what they are doing has not hurt them by now, then it never will.

    The conundrum continues because it is these patients who end up dropping out of CL wear without notice.

    For many of us, our CL volume remains stable year after year. This may seem encouraging, but it is actually a negative discovery. It means our CL practice is essentially a revolving door. Though we may not remember many patients quitting CLs this year, we know we have had many new fits.

    Think about it for a minute.

    Previously from Dr. Brimer: 9 habits for multifocal contact lens fitting success

    If we have continuous new fits, yet our CL volume is steady, then we have as many patients leaving CL wear, or the practice. This can have a significant financial impact over the life of the practice, resulting in $19,000 to $24,500 in total lost revenue per CL dropout.1

    Considering that CL dropouts often don’t give us notice or the chance to fix their situation, are there tools we can implement to predict future CL intolerance? Osmolarity testing can be one tool used.

    What osmolarity tells us

    I recently participated in a clinical trial in which 273 consecutive CL patients from seven practice sites were surveyed and their tears were measured for osmolarity. Patients were categorized as “symptomatic” if reporting more than three of the 10 potential symptoms. Abnormal osmolarity was defined as a difference of greater than 8 mOsml/L between both eyes or either eye testing over 308 mOsml/L.2

    Related: Sizing up daily disposable contact lenses

    First, let’s consider what osmolarity tells us. Symptoms of CL discomfort can mimic dry eye disease. A CL splits the tear film in half, creating a pre-lens and post-lens tear film. This causes an increase in tear film evaporation and, in some cases, CL induced dryness.

    Osmolarity measures the concentration of solutes in the tear film. The more concentrated the tear film, the higher the osmolarity. Tears become hyperosmolar when there is a decrease in aqueous production or increased evaporation due to decreased meibomian gland production.

    Crystal M. Brimer, OD, FAAO
    Dr. Brimer is a graduate of UNC-Chapel Hill and Southern College of Optometry. She is a fellow of the American Academy of Optometry and ...

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