CLINICAL

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OSD Diagnostic Advances

A slew of recent techniques have made the trial-and-error method of ocular surface disease diagnosis and management obsolete

TOM KISLAN, O.D., STROUDSBURG, PA.

It wasn’t that long ago that correctly diagnosing ocular surface disease (OSD) was a challenge, hindering an O.D.’s ability to provide the appropriate treatment from the outset. For example, as we all know too well, dry eye disease (DED) signs do not always correlate with reported patient symptoms. In addition, it is often difficult to discern between DED and ocular allergy.

Thankfully, recent advancements in OSD diagnostic techniques have aided optometrists in identifying exactly what they are dealing with, while providing tangible proof to patients. As a result, patient compliance to recommended treatment(s) has increased, leading to improved outcomes and, therefore, a growth in patient satisfaction and referrals to practices that implement one or more of these technologies.

Here, I discuss the latest diagnostic techniques for OSD.

Measuring tear osmolarity

By employing a test card that acquires nanoliters of tears from the eyelid margin and placing it in a device that calculates the volume of salt in one’s tears (osmolarity), eyecare practitioners can now determine in less than 30 seconds whether patients who present with ocular surface complaints (e.g., ocular dryness, allergies, contact lens discomfort) have tear film instability.

A higher probability of meibomian gland dysfunction is seen in patients who have a low lipid layer thickness.
PHOTO COURTESY: KATHERINE MASTROTA, O.D.

The technology, known as the TearLab Osmolarity System, was born out of research that reveals a high volume of salt in one’s tears (hyperosmolarity) is an indication of DED. Specifically, too much salt causes a high rate of tear evaporation, which leads to tear film instability, inflicting friction on the conjunctiva and corneal epithelium, which can lead to severe damage.

An osmolarity measurement of 280 and lower is normal, 280 to 300 indicates mild DED, 300 to 320 reveals moderate DED, and 320 or higher is considered severe DED. In addition, a difference of 10 between the eyes is a red flag for tear film instability.

Having a quantitative value that both doctors and patients can understand has made a huge difference is prescribing the correct treatment(s) and instilling patient compliance to treatment(s). In my practice, patients ask, “What’s my number?” As we see their ocular surface improve, we see their tear osmolarity improve through time as well.

Testing for inflammation

By placing a sterile sample collector in the palpebral conjunctiva, snapping it into a test cassette (that mimics a pregnancy test) and immersing the cassette’s tip into a buffer vial, eyecare practitioners can determine whether patients have DED vs. ocular allergy in roughly 10 minutes.

The test, InflammaDry, detects increased levels of matrix metalloproteinase-9 (MMP-9), an inflammatory marker always elevated in the tears of patients who have DED.

Identifying elevated MMP-9 is important in not only distinguishing between DED and ocular allergy, it is also crucial in classifying chronic DED patients and in pre-surgical evaluations. Missed identification of DED during pre-surgical evaluations can result in post-operative poor and/or fluctuating visual acuity, mild DED increasing in severity and epithelial ingrowth and flap slippage in LASIK patients.

Looking for biomarkers

Via a Tear Capture Device used to collect a 0.5ul tear sample from the temporal inferior lid margin, a Test Kit Well, chase solution and a scanner for results, eyecare practitioners can find out whether a patient has aqueous-deficient DED or ocular allergy in roughly 10 minutes.

Specifically, the test, the TearScan Micro Assay System, examines the tears for lactoferrin and immunoglobulin E (IgE), which are biomarkers for aqueous-deficient DED and an allergen, respectively.

Assessing lipid layer thickness

Through the assessment of more than one billion data points of an interferometric image of the tear film, eyecare practitioners can determine lipid layer thickness, aiding in the diagnosis of evaporative DED.

Known as the LipiView Ocular Surface Interferometer, the device uses a light focused on the patient’s corneal surface tear film, which is specularly reflected into a recording camera, producing an interferogram, or interference pattern in 20 seconds for each eye. In addition, the instrument acquires blink rate. A decreased blink rate has also been implicated in hindering lipid production.

Research reveals a higher probability of meibomian gland dysfunction in patients who have a low lipid layer thickness, and that DED symptom severity correlates with lipid layer thickness. Further, lipid layer thickness has been negatively associated with upper and lower meibomian gland loss.

Scanning for DED

Via meibomian gland images, a lipid layer evaluation and tear meniscus height and tear film breakup time measurements, through non-invasive scanning software, eyecare practitioners can acquire qualitative and quantitative tear film data in roughly five minutes, aiding in the DED diagnosis.

The device, the Oculus Keratograph, also includes a corneal topographer and keratometer to facilitate optimum contact lens fits.

Anterior segment photography has proven significant in terms of instilling patient compliance to our prescribed treatments. For example, when patients see their blocked meibomian glands, they become more aware of their disease and, thus, the importance of doxycycline, lid scrubs and warm compresses.

Providing solutions

Through the use of the aforementioned diagnostic techniques, optometrists can now achieve a definitive diagnosis, enabling the correct treatment from the start, which allows for faster symptom relief. In using a couple of these devices myself, I can tell you that they have helped me to create a dry eye center of excellence, which has lead to exponential practice growth. Patients become loyal and refer others to practitioners who can provide them with quick results. OM

Dr. Kislan is owner and medical director of Stroudsburg Eye Specialists, Hazleton Eye Specialists and the Dry Eye Clinic of Northeast PA. He lectures on dry eye disease and glaucoma and has no financial interest in any of the products mentioned. Send comments to optometricmanagement@gmail.com.