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One problem we face when managing dry eye patients is that signs and symptoms often dont correlate. Consider: Researchers from Ohio State University studied 75 patients with varying types and severity of dry eye disease.1 They asked patients about symptoms, then performed a clinical exam only to find that symptoms were generally not associated with clinical signs, even after adjusting for age and use of artificial tears.
This leaves us with a quandary, they say. Indeed, which test can best help us diagnose dry eye in patients?
History
A good history is often the best determinant of dry eye disease, so patient questionnaires would appear to be a good diagnostic test. Examples include the McMonnies Dry Eye Index, the National Eye Institute Visual Functioning Questionnaire (NEI VFQ-25) and the Ocular Surface Disease Index (OSDI).
Studies show a modest to strong association of these tests with a dry eye condition. Researchers found that the OSDI was valid, effectively discriminating between normal, mild to moderate and severe dry eye disease as defined by clinical assessment and a composite disease severity score.2 They also found that the OSDI correlated significantly with the McMonnies questionnaire, the NEI VFQ-25, the physical component summary score of the Short Form-12 Health Status Questionnaire, the patients perception of symptoms and artificial tear usage.3
TBUT of less than 10 seconds is considered significant for dry eye. To optimize reliability of this test, researchers suggest taking five measurements and averaging the three closest measurements.4
Also, the Dry Eye Test (DET)-modified fluorescein strip (Akorn) may provide more consistent measurements than a standard fluorescein strip for assessing dry eye. In one study, researchers used fluorescein strips in one eye and DET strips in the other.5 In three consecutive measurements on 75 patients, the researchers found that DET values were within three seconds of each other for 96% of the patients. TBUT values with the standard strips were within three seconds of each other for 71% of the patients. Patients were less likely to report sensation upon application of the DET strip compared to the conventional one.
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| Researchers suggest using the closest three out of five TBUT measurements. |
Vital Dyes
Vital dyes such as lissamine green or rose bengal are becoming more common for ocular surface staining, particularly of the conjunctiva. One key difference: Patients tolerate lissamine green better than rose bengal. For example, patients in one study noted greater and longer-lasting adverse symptoms when stained with rose bengal, especially patients with keratoconjunctivitis sicca, than when stained with lissamine green.6 The same study showed no difference in objective staining scores, concluding that lissamine green is just as effective as rose bengal, but it does not cause adverse reactions.
Another study revealed that rose bengal damages the viability of human corneal epithelial cells.7 For that reason, the authors suggest using lissamine green for evaluating ocular surface disorders.
Tear Meniscus Height
This quick, easy assessment of the tear volume on the lower lid shows a good correlation to changes in dry eye.8 The tear meniscus height indicates whether minimal tear film exists. It also helps us evaluate the quality of tears. For example, heavy debris would indicate poor quality.
Also, this test may be a good precursor to performing a Schirmer test or phenol red thread test. If you observe a normal tear meniscus height, then you might not want to pursue a Schirmer test to confirm dry eye because the patient probably has ample tear volume. The tear quality may not be there, but the Schirmer test does not measure that. If you observe a scant tear meniscus height, a Schirmer tear test is warranted to confirm the diagnosis of dry eye.
Schirmer Tear Test
Critics question the validity of the Schirmer test due to reflex tearing and inconsistencies such as the amount of tears already present in the fornix, and perhaps a lack of consistent protocol for performing the test. Still, several studies show a correlation between the Schirmer or the phenol red thread tests to desiccation of the cornea as measured by fluorescein, TBUT and vital dye staining.9
The Schirmers-I-test (without anesthesia) and rose bengal staining may be valuable for confirming a diagnosis of Sjgrens syndrome in individuals who report a history of dry eye and dry mouth.10 A value of about zero on the Schirmer test (without anesthesia) is often a final diagnostic determinant for confirming this condition.11 (Of course, you may need to refer the patient for testing of the dry mouth component.)
Although we still need further diagnostic tests to confirm dry eye disease, patient questionnaires or history, TBUT and evaluation of tear meniscus height appear to be reproducible and can help us arrive at the correct diagnosis.12 Lissamine green dye appears as effective as rose bengal, but without the adverse effects. Meanwhile, the Schirmers tear tests may play a key role in the diagnosis of conditions such as Sjgrens syndrome.
Dr. Karpecki is director of research for the Moyes Eye Center in Kansas City, Mo. He has no financial interest in any products mentioned here.
1. Nichols KK, Nichols JJ, Mitchel GL. The lack of association between signs and symptoms in patients with dry eye disease. Cornea 2004 Nov;23(8):762-70.
2. Schiffman RM, Christianson MD, Jacobsen G, et al Reliability and validity of the Ocular Surface Disease Index. Arch Ophthalmol 2000 May;118(5):615-21.
3. Vitale S, Goodman LA, Reed GF, Smith JA. Comparison of the NEI-VFQ and OSDI questionnaires in patients with Sjgrens syndrome-related dry eye. Health Qual Life Outcomes 2004 Sep 01;2(1):44.
4. Cho P. Reliability of a portable noninvasive tear break-up time test on Hon Kong-Chinese. Optom Vis Sci 1993 Dec;70(12):1049-54.
5. Korb DR, Greiner JV, Herman J. Comparison of fluorescein break-up time measurement reproducibility using standard fluorescein strips versus the Dry Eye Test (DET) method. Cornea 2001 Nov;20(8):811-5.
6. Manning FJ, Wehrly SR, Foulks GN. Patient tolerance and ocular surface staining characteristics of lissamine green versus rose Bengal. Ophthalmology 1995 Dec;102(12):1953-7.
7. Kim J, Foulks GN. Evaluation of the effect of lissamine green and rose Bengal on human corneal epithelial cells. Cornea 1999 May;18(3):328-32.
8. Miller WL, Doughty MJ, Narayanan S, et al. A comparison of tear volume (by tear meniscus height and phenol red thread test) and tear fluid osmolality measures in non-lens wearers and in contact lens wearers. Eye Contact Lens 2004 Jul;30(3):132-7.
9. Nichols KK, Nichols JJ, Lynn Mitchell G. The relation between tear film tests in patients with dry eye disease. Ophthalmic Physiol Opt 2003 Nov;23(6):553-60.
10. Vitali C, Moutsopoulos HM, Bombardieri S. The European Community Study Group on diagnostic criteria for Sjgrens syndrome. Sensitivity and specificity of tests for ocular and oral involvement in Sjgrens syndrome. Ann Rheum Dis 1993 Oct;53(10):637-47.
11. Stankusheva T, Boiadzhieva P, Antonova N. [Sjgrens syndrome.] Vutr Boles 1987;26(5):131-4.
12. Nichols KK, Mitchell GL, Zadnik K. The repeatability of clinical measurements of dry eye. Cornea 2004 Apr;23(3):272-85.
