Diagnostic tools allow clinicians the opportunity to effectively assess the underlying cause and diagnose dry eye earlier in the disease process.
Traditional diagnostic tools
Several dry eye diagnostic tests such as Schirmer's test, phenol red thread (PRT) test, tear break-up time (TBUT), and ocular surface staining have been available for decades and remain important tools for DED diagnosis.
The most common tests for measuring aqueous production are Schirmer's and PRT. Although most physicians use Schirmer, studies have found PRT to be equally reliable and perhaps more beneficial for patients.5
PRT is more comfortable for the patient, does not require an anesthetic, and takes significantly less time to perform, taking about 15 seconds per eye while the Schirmer's test takes 5 minutes.
TBUT is the most frequently used diagnostic test for tear film instability. TBUT uses a fluorescein strip to measure the average seconds between a blink and the appearance of a dark spot in the fluorescein. A TBUT of 10 seconds or less is considered indicative of dry eye; healthy eyes without DED have an average TBUT of 27 seconds.6
Lissamine green and rose bengal fluorescein detect superficial damage to the ocular surface by staining areas not covered by mucin. Conjunctival ocular surface staining is indicative of early-stage DED. Sodium fluorescein staining can be used to stain the cornea if advanced DED is suspected.
Although ocular surface staining cannot be used to differentiate disease, it can tell clinician how far advanced the disease is and if dry eye treatments are working.
1. Dana R, Bradley JL, Guerin A, et al. Estimated Prevalence and Incidence of Dry Eye Disease Based on Coding Analysis of a Large, All-age United States Health Care System. Am J Ophthalmol. 2019;202:47-54.
2. Schein OD, Tielsch JM, Munoz B, et al. Relation between signs and symptoms of dry eye in the elderly. A population-based perspective. Ophthalmology. 1997;104(9):1395-401.
3. Begley CG, Chalmers RL, Abetz 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;44(11):4753-61.
4. Ngo W, Situ P, Keir N, et al. Psychometric properties and validation of the Standard Patient Evaluation of Eye Dryness questionnaire. Cornea. 2013;32(9):1204-10.
5. Vashisht S, Singh S. Evaluation of Phenol Red Thread test versus Schirmer test in dry eyes: A comparative study. Int J Appl Basic Med Res. 2011;1(1):40-2.
6. Sweeney DF, Millar TJ, Raju SR. Tear film stability: a review. Exp Eye Res. 2013;117:28-38.
7. Craig JP, Nelson JD, Azar DT, et al. TFOS DEWS II Report Executive Summary. Ocul Surf. 2017;15(4):802-12.