diagnosis

Dry Eye Diagnosis: Time to Update Your Toolkit

How do you best diagnose a multi-factorial disease?

Scot Morris, O.D., F.A.A.O. Conifer, Colo.

With all the new technology available, it's very easy to get caught up in looking for the one test that tells you that your patient has dry eyes. If you haven't yet found the test, don't fret. Why? Well, in short, there isn't one. The reason, in part, is because dry eye disease is a multi-factorial disease that affects many different parts of the ocular surface with differing levels of severity in each individual.

As a general disease, dry eye encompasses many different subtypes and four levels of severity, as laid out by the International Task Force on Dry eye (ITF) panel in the Dry Eye Workshop (DEWS) guidelines.¹ (See “Four Levels of Dry Eye,” at the end.) Much like glaucoma, there is no substitute for the trained ear, the trained observer and experience. However, through a combination of a comprehensive patient history, a few subjective diagnostic tests and a few new objective diagnostic devices, the optometric physician can compile the necessary information to make the correct diagnosis. This article will review some of the more traditional diagnostic modalities as well as incorporate how the new technologies fit into this diagnostic landscape.

The challenge of history

The methodical history still remains the single most important diagnostic test that is performed. Undoubtedly, there is such a range of patient descriptions that this step can be daunting to many clinicians. Whether the clinician utilizes a standardized test, such as the Ocular Surface Disease Index or one of the other patient questionnaires available on the market, they must ask a series of questions that will help them identify which of the many forms of dry eye with which they are dealing.

Symptoms, such as itching, may signal allergy or some form of lid margin disease. A patient reporting that their eyelids are stuck together early in the morning and that they experience chronic tearing in certain environmental conditions may suggest evaporative dry eye issues related to posterior blepharitis and more specifically meibomian gland disease.² Symptoms such as chronic irritation that increases toward the end of the day with visual fluctuations may suggest an aqueous deficient subtype of dry eye. Each of these pieces of information on their own may not make the diagnosis, but when the series of answers are compared with subjective clinical observations and more objective data analysis, a clear picture may be ascertained.

Clinical observations

The next few tests involve observation without the slit lamp. Evaluation of the unaltered blink rate, facial and dermatological status, facial symmetry and a cursory evaluation of the lid margin are all necessary and should be performed before the slit lamp is utilized. The blink rate, especially in relation to the tear break-up time (TBUT) may be one the most sensitive indicators of dry eye disease.³

For example, if the patient's TBUT is faster than their normal blink rate, their ocular surface is exposed, and the patient is likely symptomatic. Conversely, if the blink rate is faster than the TBUT, the patient is likely non-symptomatic regardless of the clinical observations.

Facial observation may yield clues to exposure issues, including incomplete blink or dermatological issues, such as rosacea. Once these have been evaluated, undertake a more comprehensive evaluation of the lid margin with the slit lamp.

There has been a tremendous amount of discussion through the last few years about the role of the eyelid in ocular surface disease and the various forms of lid margin disease. Currently, there is no diagnostic device other than the slit lamp—and experience—to evaluate the lid margin and the various forms of seborrheic, anterior and posterior blepharitis. Undoubtedly, the lid margin plays a significant role in many forms of ocular surface disease because of its proximity to the ocular surface, as well as the fact the outer lipid layer of the tear film is derived from the meibomian glands within the posterior eyelid. (Shortly, a Delphi panel, an international group of dry eye experts, will convene to determine lid margin guidelines.)

Evaluate the ocular surface

Next is an evaluation of the tear film and ocular surface. First an overview of the bulbar conjunctiva should be performed to evaluate for the presence of hyperemia, edema, conjunctival chalasis—any or all of which may suggest the presence of one of the many forms of ocular surface inflammation. The cornea should be evaluated for any epithelial defects, corneal pannus, or neovascularization, which may suggest ocular surface hypoxia and/or generalized inflammation. Anterior segment optical coherence tomography (AS-OCT) may be used to diagnose corneal thinning disorders, such as keratoconus, and other posterior corneal diseases.⁴ As it provides blur-free imaging and precise measurement of the tear meniscus, AS-OCT is expected to become a valuable technique in dry eye screening and diagnosis.

Consider using slit lamp photography to photo document the general presentation of the ocular surface. Slit lamp photodocumentation is especially helpful for trend analysis and monitoring whether the selected therapy is having a positive effect on the clinical signs.

A test for tear film

After these diagnostic observations, we may want to evaluate the tear film itself. Until recently, tear film osmolarity testing using either freezing point depression or vapor pressure was limited to research institutions. A new diagnostic device on the market is able to measure the tear film osmolarity via electrical impedance (TearLab Osmolarity Test, Tear-Lab Corporation). This portable device allows for small sample measurements (50nL) in the optometric office.

Tests to dye for

Use the vital dyes to assess the integrity of the ocular surface. Both sodium fluorescein and lissamine green (or rose bengal) staining should be used, as they test different parts of the ocular surface and tear film. After the initial instillation of sodium fluorescein, the clinician should measure the TBUT. Many of the new topographers and visual aberrometers may provide a more precise measure of TBUT because they are noninvasive, but sodium fluorescein also works well and provides a convenient method of testing tear film.⁵ Shortly after you record the TBUT, observe the ocular surface staining, and then document it through photography and/or video.

Many clinicians then perform some measure of quantitative tear volume analysis, which may include the Schirmer test, Phenol red thread test or just a general subjective tear film observation. Many clinicians put little weight on Schirmer test results due to concerns regarding the test's reliability.⁶

Once a thorough evaluation of the ocular surface is performed, it is advisable to go back to the lid margin and press on the meibomian glands to evaluate the viscosity of the meibomian gland. You can also make any other observations that may have been necessary to avoid earlier in the exam process so as to not alter the results of earlier tests.

Using all the tools

Although what has been illustrated in this article was a brief overview of diagnostic testing related to dry eye, remember that even the most experienced clinician cannot diagnose dry eye or differentiate it without performing and evaluating—in large part or in whole—a complete series of diagnostic tests. The latest and greatest technology undoubtedly significantly increases the knowledge of the type of ocular surface disease with which the patient presents. This battery of tests still needs to be performed to differentiate the various forms of ocular surface disease as well as to identify coexisting or concomitant disease states. OM

1. The definition and classification of dry eye disease: Report of the Definition and Classification Subcommittee of the International Dry Eye Workshop (2007). Ocul Surf. 2007 Apr;5(2):75-92.
2. Bowman RW, Dougherty JM, McCulley JP. Chronic Blepharitis and Dry Eyes. Int. Ophthalmol Clin. 1987 Spring;27(1):27-35.
3. Vanley GT Leopold IH Gregg TH. Interpretation of Tear Film Break-up. Arch Ophthal. 1977 March. 95:445-448.
4. Qiu X, Gong L, Sun X, Jin H. Age-related Variations of Human Tear Meniscus and Diagnosis of Dry Eye With Fourier-domain Anterior Segment Optical Coherence Tomography. Cornea. 2011 May;30(5):543-9.
5. Mengher LS, Pandher KS, Bron AJ. Non-invasive tear film break-up time: sensitivity and specificity. Acta Ophthalmol (copenh.) 1986 Aug;64:441-444.
6. Lamberts DW, Foster CS, Perry HD. Schirmer test after topical Anesthesia and the tear meniscus height in normal eyes. Arch Ophthamol. 1979 Jun;97(6):1082-1085.

Dr. Morris is the director of Eye Consultants of Colorado, LLC and Morris Education & Consulting Associates. He is a member of the American Optometric Association and is a Fellow of the American Academy of Optometry. E-mail him at smorris@eyeconsultantsofco.com, or send comments to optometricmanagement@gmail.com.