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    How tear osmolarity affects lens wear

    Diagnosing, treating osmolarity efficiently may lead to less CL dropout

     

    In this state, tears can become toxic to the corneal epithelium. Toxicity can then lead to a loss of glycocalyx and microvilli, which are responsible for attracting and retaining water on the corneal surface. Instability of the tear film and lack of wettability can cause epithelial cell damage, goblet cell loss, inflammation, and even cell death.

    Nerve fibers and underlying cells are then exposed, and damage progresses. As surface wettability decreases, it affects the way light is reflected, causing increased aberrations and visual strain for the patient. This is amplified in those wearing CLs, often inducing fluctuating vision that varies with the blink, or the need to blink more frequently.

     

    How osmolarity is applicable

    When surveyed, 69 percent of all CL wearers in the study were symptomatic. This begs the question: Are we asking the right questions in the exam room to uncover that potentially 69 percent of our wearers are symptomatic?

    Ask specific questions to better screen your patients. Don’t wait for them to complain!

    Of these symptomatic patients, three out of five had abnormal osmolarity. As expected, a higher percentage of CL wearers were hyperosmolar in the symptomatic group vs. the asymptomatic group, but there was not a big differential between the two groups (60 percent vs. 55 percent).

    Related: Connecting allergy and osmolarity

    This is a reminder to us of the impact of contact lens wear to the ocular surface, even in patients without current symptoms.

    Research shows multiple inflammatory mediators, such as interleukin IL-6 and IL-8, are upregulated in the tears of CL wearers.3 It also has been shown that both tear break-up time (TBUT) and tear volume are significantly reduced in CL wearers. It seems plausible that osmolarity would be increased in a significant portion of CL wearers, regardless of their symptoms.4

    Interestingly, of the 59 percent who tested hyperosmolar, 70 percent of those were surveyed to be symptomatic. It would be beneficial to know if and when the other 30 percent become symptomatic.

    With that in mind, perhaps osmolarity can be used as a meaningful marker in determining the tear film balance, thereby predicting the likelihood of future discomfort and potential dropout. It would be helpful to identify any increase in osmolarity over time. If a patient is asymptomatic but hyperosmolar, watch for progression and/or future onset of symptoms.

    Consider being proactive and implementing solution, material, modality, or behavioral changes now, as well as some form of treatment. Discuss diet, water intake, wearing habits, and simple lid hygiene at the least.

    The number of symptoms reported and frequency of the symptoms was similar among patients with normal and abnormal osmolarity. This indicates that symptoms alone may not be an adequate indicator of ocular surface stress.

    Related: How to use tear osmolarity to help treat dry eye disease

    So, if a large percentage of CL wearers are symptomatic, how do we know which ones might progress and drop out?

    Determining dropout patients

    It is reasonable to assume that patients with more concentrated tears might progress to a state of hydrophobicity and quickly evolve to experience greater discomfort and structural consequence.

    If a patient is symptomatic and hyperosmolar, implement a treatment now to prevent progression. Also, consider an immediate change to the patient’s material, solution, or wearing habits. Use osmolarity as a conversation starter to motivate patients to convert to daily disposable CLs.

    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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