When patients present with suspected dry eye, we must decide which test is most appropriate.
Research from Ohio State University College of Optometry shows that clinicians choice of tests depends on myriad factors, including time constraints. The order of preference: patient history, fluorescein staining, tear break-up time (TBUT), tear assessment, Schirmers test and rose Bengal staining.1
Proper Testing
Patients complaints may have a higher correlation to dry eye severity than clinical signs and objective tests.2 Ask what symptoms occur and when, and from what tasks. Symptoms tend to be greater in the evening.2
Clinical testing to confirm the diagnosis and establish a treatment plan then includes:
Fluorescein staining. Fluorescein can show punctate staining patterns related to dry eye or inflammation or via delayed fluorescein clearance. Typical dry eye staining often appears in the exposure areas of the cornea and sometimes inferiorly (although this can also point to lagopthalmos, an incomplete blink alone or secondary to an event such as a seventh nerve palsy).3 Testing may yield more definitive results if you administer sufficient fluorescein (but not too much), wait 1-2 minutes and use a filter to enhance staining.4
Fluorescein clearance can be an effective tool for diagnosis even when tear volume tests are normal.5 Researchers instilled 5 microls of 2% fluorescein and measured the concentration in the patients eye after 15 minutes. The test was 95% sensitive and 97% specific for aqueous tear deficiency.6
TBUT. Less than 5 seconds is considered abnormal, but the effectiveness of this test depends on technique. Too much or too little dye will vary the results.7
Dry eye in Sjgrens syndrome. A scant tear meniscus is present, and rose Bengal shows diffuse bulbar staining. Courtesy: Kimberly Reed, O.D.
Tear meniscus. The height of the tear meniscus appears to be a powerful predictor of tear film insufficiency.8 Photo and video measurements and reflective meniscometry all correlate to ocular surface disease.9,10
Tear volume tests. Schirmers and phenol thread tests are easy to perform, but with improper technique, results may vary, and the test may have poor reproducibility.11,12
There appears to be a correlation between tear volume tests and corneal staining.13 A reading of less than 5mm on Schirmers test confirms a diagnosis of Sjgrens syndrome in symptomatic patients.14
Vital dyes. Lissamine green has a similar staining effect to rose Bengal, though lissamine green does not sting and wont last as long in the eye.15
Lissamine green usually stains the conjunctival surface in the exposure areas of 3 and 9 oclock. Both dyes can stain areas of the ocular surface that are not protected by mucin. This tells us about the quality of the mucin layer of the tear film.
Dry eye testing offers us tools to confirm our diagnosis. These tests will become even more important as the prevalence of dry eye grows.
1. Nichols KK, Nichols JJ, Zadnik K. Frequency of dry eye diagnostic test procedures used in various modes of ophthalmic practice. Cornea 2000 Jul;19(4):477-82.
2. Begley CG, Chalmers RL, Abbetz L et al. The relationship between habitual patient-reported symptoms and clinical signs among patients with dry eye of varying severity. Invest Ophthalmol Vis Sci. 2003 Nov; 44(11):4753-61.
3. Marsh PB, Schwab IR. Corneal surface disease topology. Int Ophthalmol Clin 1998 Fall;38(4):1-13.
4. Bron AJ, Evans VE, Smith JA. Grading of Corneal and conjunctival staining in the context of other dry eye tests. Cornea. 2003 Oct; 22(7):640-50.
5. Afonso AA, Monroy D, Stern ME, et al. Correlation of tear fluorescein clearance and Schirmer test scores with ocular irritation symptoms. Ophthalmology 1999 Apr;106(4):803-10.
6. Macri A, Rolando M, Pflugfelder S. A standardized visual scale for evaluation of tear fluorescein clearance. Ophthalmology 2000 Jul; 107(7):1338-43.
7. Cho P, Brown B. Review of the tear break-up time and a closer look at the tear break-up time of Hong Kong Chinese. Optom Vis Sci 1993 Jan;70(1):30-8.
8. Mainstone JC, Bruce AS, Golding TR. Tear meniscus measurement in the diagnosis of dry eye. Curr Eye Res 1996 Jun;15(6):653-61.
9. Oguz H, Yokoi N, Kinoshita S. The height and radius of the tear meniscus and methods for examining these parameters. Cornea 2000 Jul;19(4):497-500.
10. Yokoi N, Bron AJ, Tiffany JM, Kinoshita S. Reflective meniscometry: a new field of dry eye assessment. Cornea. 2000 May;19(3 Suppl): S37-43.
11. Kallarackal GU, Ansari EA, Amos N et al. A comparative study to assess the clinical use of Fluorescein Meniscus Time (FMT) with Tear Break up Time (TBUT) and Schirmers tests (ST) in the diagnosis of dry eyes. Eye 2002 Sep;16(5):594-600.
12. Tomlinson A, Blades KJ, Pearce EI. What does the phenol red thread test actually measure? Optom Vis Sci. 2001 Mar; 78(3):142-6.
13. 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.
14. 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 Disease 1994 Oct;53(10):637-47.
15. Kim J. The use of vital dyes in corneal disease. Curr Opin Ophthalmol 2000 Aug;11(4):241-7.