Don’t Pass the Salt: Measuring Tear Osmolarity and Its Impact on Dry Eye Disease

Dry eye disease is a multifactorial disease that can cause a wide variety of symptoms. Due to its complexity, diagnosing dry eye can be difficult. Although there is no definitive gold standard dry eye diagnostic test, testing tear osmolarity has risen to be one of the best ways to determine the presence of dry eye disease. [1] [2] Testing tear osmolarity refers to measuring the salt concentration in tears, where abnormal results can indicate an imbalance in the tear film. Furthermore, testing tear osmolarity can help eye care professionals monitor the effectiveness of dry eye treatments.

Composition of the tear film

Tears are composed of three layers: the mucin layer, the aqueous layer, and the lipid layer. The mucin layer is the inner layer that keeps the eyes lubricated, the aqueous layer is the water-based middle layer that washes away particles and prevents infections, and the lipid layer is the oil-based outer layer that helps reduce the evaporation of natural tears. Issues with any of these layers in the tear film can cause instability and result in tear imbalances and dry eye. An adequate and consistent layer of tears on the surface of the eye is essential to keeping eyes healthy, comfortable, and seeing well. Tears clear the eye’s surface to keep it moist and wash away dust, debris, and microorganisms that could damage the cornea and lead to an eye infection or other complications.

Measuring tear osmolarity for dry eye disease

Tear osmolarity is the measurement of the salt concentration in tears. In a healthy tear, the concentration of salt falls within a narrow and specific range. A measurement of more than 300 milliosmoles per litre or an inter-eye difference of more than 8 milliosmoles per litre is considered abnormal. [3] And so, if the measurement falls in this abnormal range, the salt concentration within the tear will be elevated. This high or abnormal level of osmolarity (known as hyperosmolarity) occurs when the lipid layer is too thin, which causes the water in the tears to evaporate quickly, thus causing the remaining water to have a higher concentration of salt. [4] If the tears evaporate too quickly, the eye does not have the opportunity to become properly lubricated, which leads to a wide array of uncomfortable symptoms. Suffering from hyperosmolarity can range from ocular discomfort to posing great risks towards ocular health, especially if left untreated. Symptomatically, hyperosmolarity can cause significant stress to the cornea which increases inflammatory levels. [5] Due to the ocular inflammation, hyperosmolarity can cause damage towards multiple components of the ocular surface, which can ultimately lead to a progressive deterioration of the cornea and can develop into a chronic disorder. Plus, as discussed, healthy tears help wash away dust, debris, and microorganisms that could damage the cornea and lead to an eye infection. Hyperosmolarity can then cause a patient to be more susceptible towards a wide array of ocular infections and complications.

Tear osmolarity effectiveness

A 2011 study from the American Journal of Optometry that evaluated the use of tear osmolarity in the diagnosis of dry eye disease concluded that tear osmolarity is the best single metric both to diagnose and classify dry eye disease. [6] Measuring tear film osmolarity is an appealing test because it offers a numerical value for dry eye — something that most other dry eye tests lack.?[7] The test is also helpful because it can be used to differentiate dry eye disease from other conditions that can cause similar symptoms. [8] It is also key in being used to help monitor the effectiveness of dry eye treatments such as artificial tears, heat therapy, changes in ocular hygiene, and nutrition.

Measuring tear osmolarity: I-PEN??from I-MED Pharma

The I-PEN? from I-MED Pharma is a state-of-the-art measurement tool to help diagnose dry eye, which measures tear osmolarity in seconds. The I-PEN?, used in conjunction with the I-PEN??Single Use Sensors (SUS), provides a quick and simple method for determining tear osmolarity of the tissues bathed in the tear film of the orbital tissues such as the palpebral conjunctiva. After approximately 2 seconds of contact with the eyelid tissue, the I-PEN??Tear Osmolarity System will display a quantitative tear osmolarity test result on the liquid crystal display (LCD) in units of mOsms/L. No calculations are required. The I-PEN??Tear Osmolarity System utilizes an impedance measurement to provide an indirect assessment of osmolarity of the tear film of the eye.

The I-PEN??Tear Osmolarity System is designed for use as an in-practice measurement tool both for patients presenting with dry eye symptoms and for all pre-and post-surgical patients. In addition, the I-PEN??Tear Osmolarity System is an invaluable asset for monitoring the progress of dry eye treatment therapies.

The I-PEN??Tear Osmolarity System is for professional in-vivo use only.

How to use the I-PEN? from I-MED Pharma

Measuring tear osmolarity has risen to be one of the most important tests to help diagnose dry eye, as well as monitor the condition more effectively. The test itself is quick, efficient, non-invasive, and causes no pain or discomfort to the patient. The I-PEN??by I-MED Pharma allows for an easy and efficient way to measure tear osmolarity, with its sleek design and its quick ability to provide an accurate calculation. The I-PEN? provides important information to the doctor to be able to help diagnose dry eye and therefore get their patients on a management plan quickly. It helps eye care professionals have the ability to monitor the effectiveness of dry eye treatments, by allowing them to follow-up accordingly to see if results are improving.

Learn more about the innovative I-PEN? Tear Osmolarity System and how it can help you in your practice.

Originally published June 4th, 2024 at imedpharma.com.

[1] Potvin R, Makari S, Rapuano CJ. (2015, November 2) Tear film osmolarity and dry eye disease: a review of the literature. Clin Ophthalmol. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4636089/

[2] Lemp MA, Bron AJ, Baudouin C, Benítez Del Castillo JM, Geffen D, Tauber J, Foulks GN, Pepose JS, Sullivan BD. (2011, May). Tear osmolarity in the diagnosis and management of dry eye disease. American journal of ophthalmology. https://pubmed.ncbi.nlm.nih.gov/21310379/

[3] Nguyen, D., & Miranda, T. (2020, November 17).?Tear osmolarity explained. My Dry Eye.

[4] Lazarus, R. (2021, November 21).?Does tear osmolarity indicate dry eyes?. Optometrists.org. https://www.optometrists.org/general-practice-optometry/guide-to-eye-conditions/dry-eye/does-tear-osmolarity-indicate-dry-eyes/#:~:text=Tear%20osmolarity%20is%20a%20measure,ocular%20surface%20disease%20(OSD).

[5] Mannis, M. J., Holland, E. J., & Lee, W. B. (Eds.). (2013). Ocular Surface Disease: Cornea, Conjunctiva and Tear Film. https://www.sciencedirect.com/book/9781455728763/ocular-surface-disease-cornea-conjunctiva-and-tear-film#book-description

[6] Lemp MA, Bron AJ, Baudouin C, Benítez Del Castillo JM, Geffen D, Tauber J, Foulks GN, Pepose JS, Sullivan BD. (2011, May). Tear osmolarity in the diagnosis and management of dry eye disease. American journal of ophthalmology. https://pubmed.ncbi.nlm.nih.gov/21310379/

[7] Hessen, M. (2018, May 15).?All about osmolarity. Review of Optometry. https://www.reviewofoptometry.com/article/all-about-osmolarity

[8] Mannis, M. J., Holland, E. J., & Lee, W. B. (Eds.). (2013). Ocular Surface Disease: Cornea, Conjunctiva and Tear Film. https://www.sciencedirect.com/book/9781455728763/ocular-surface-disease-cornea-conjunctiva-and-tear-film#book-description