Clinical Investigation of Dry Eye Disease

Although a number of methods have been developed in the evaluation of dry eye, this disease has proven to be challenging

objective testing quantitative measurements methods however, a lack of methods has long precluded the development of specific and sensitive testing. (e.g., Schirmer testing) can be used to grade the severity of the disease and monitor for improvement over time.

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Corneal Staining

The clinical ocular health evaluation often involves the use of vital dyes. These dyes are unique in their ability to penetrate living cells without damaging them; thus, they are valuable tools in the clinical ophthalmic examination. The most commonly used topical ophthalmic dyes include sodium fluorescein, lissamine green, and rose bengal. While there are numerous clinical applications for dyes in eye care (e.g, visualizing retinal blood flow via fluorescein angiography), this article will focus on their role in cornea and tear film assessment.

Sodium Fluorescein

Sodium fluorescein (NaFl) is by far the most common dye used in the eye care setting. It is an orange, water-soluble dye that stains dead and devitalized cells.

• Common tests using NaFl

• Evaluation of corneal/conjunctival staining

• Tear meniscus height

• Tear break-up time

• Seidel testing

• Goldmann applanation tonometry

Lissamine Green

(not to be used)

Rose Bengal

Tear Break-Up Time

Background. Non-invasive, quantitative measurement of tear film stability. Measures the length of time the tear film remains on the ocular surface before evaporating.

Procedure. Sodium fluorescein is instilled in the eye. Using a cobalt blue filter, a diffuse slit lamp beam is focused on the cornea and tear film. The patient is asked to blink, then hold his or her eye open without blinking. Immediately after blinking, the surface of the cornea should appear uniformly coated in NaFl. The physician counts the seconds until the appearance of the first “break” in the tear film. This appears as patches of darkness that disrupt the uniform distribution of dye.

Findings. TBUT of 20-30 seconds is considered normal; <10 seconds is considered abnormal.

“In vivo confocal microscopy of toxic keratopathy” by Chen Y, Le Q, Hong J, Gong L, and Xu J. Licensed under CC BY-NC-ND 4.0 .

Schirmer Testing

Background. Both Schirmer tests are quantitative measurements of tear production. Test can be performed with (Schirmer I) or without (Schirmer II) the use of topical anesthetic. Anesthetizing the eye prevents reflex tearing triggered by the corneal touch response; thus, Schirmer I is a measurement of basal tear secretion only. Schirmer II is a measurement of both basal and reflex tear secretion.

Equipment. A Whartmann-1 paper strip, sodium fluorescein, topical ophthalmic anesthetic, and slit lamp bio microscope with Wrattan filter.

Procedure. If Schirmer II is being performed, topical anesthetic is instilled into the eye(s) being tested. For Schirmer I testing, skip this step. A small fold is created at the end of the Whartmann-1 strip and inserted into the lower conjunctival fornix. The patient is instructed to keep his or her eyes closed for 5 minutes. the strip is removed. The length of saturation of the strip is measured.

Findings.

Tear Osmolarity Testing

Background. Osmolarity (OsM) is a measurement of solute concentration. Measurements of tear film osmolarity are typically elevated in dry eye.

Equipment.