discovering dry eye

Rose Bengal or Lissamine Green?

BY CAROLYN G. BEGLEY, OD, MS
MARCH 1999

Rose bengal staining of the conjunctiva is a standard test in the diagnosis of dry eye. But it hurts, especially in dry eye patients. Lissamine green stains the conjunctiva similarly but doesn't hurt.

What's Behind the Ouch?

Studies have shown that lissamine green dye works by diffusing into cells with damaged membranes. Therefore, it stains injured or dead cells on the surface of the eye, and is not toxic to those cells. Rose bengal dye, on the other hand, is actually toxic to corneal epithelial cells in tissue culture. It can enter any cell, damaged or not. When instilled into the normal eye, it doesn't stain because its entry is blocked by the bound mucin layer that covers the healthy cornea and conjunctiva. However, when instilled into a pathologically dry eye where the mucin layer has been disrupted by ocular surface disease, the dye is allowed in and presumably exerts a toxic effect on the ocular surface cells stained by the dye.

Aesthetic Value

Rose bengal staining is also very visible and lasts several hours, so patients are sometimes reluctant to return to work after instillation of the dye. Lissamine green is a fainter stain than rose bengal and is more diffuse in appearance. Because it's harder to see, it's important to observe the conjunctiva carefully for signs of staining. Lissamine green also washes out of the bulbar conjunctiva rather quickly. Therefore, it is essential to observe the patient within five minutes of instillation to see the full staining pattern. The area of the conjunctiva stained by the dye is considered damaged and would also stain with rose bengal.

Lissamine green staining is retained on the lid margins as a bluish-green line, so it is visible for at least 1/2 hour after its instillation. It can't easily be washed off of the lid margin, which may cause some patients to complain of the poor cosmetic appearance. Lissamine green dye stains the skin for a long time, so it's important not to drip any outside of the eye. Lissamine green is now available in strip form, so it's easy to use. If it is instilled carefully and evaluated quickly, lissamine green staining is a rapid and painless method to assess the conjunctival health of dry eye patients.

Final Thoughts

A recent study at Indiana University, in cooperation with Dr. Barbara Caffrey, has verified that lissamine green and rose bengal stain the same areas of the conjunctiva. Figures 1a and 1b show the temporal conjunctival of one of our study patients stained with rose bengal and lissamine green at different times.

Lissamine green dye can be used rather than rose bengal to identify conjunctival damage in dry eye patients. Clinically, it stains the same areas, and it doesn't hurt. There is no longer any reason to subject dry eye patients to rose bengal.