The use of trypan blue to distinguish Pseudo-Seidel sign from lacrimal ductule versus glaucoma drainage device leakage.

INTRODUCTION: The superotemporal fornix location of the lacrimal gland ductule openings coincides with the typical locations of glaucoma drainage devices; as a result, a conjunctival fistula may look and behave like a lacrimal gland ductule. External morphology and Seidel test are helpful in identifying fluid flow but cannot differentiate the fluid as aqueous humor or tears. We describe a novel technique in differentiating a lacrimal gland ductule from a conjunctival fistula secondary to a glaucoma drainage device.

CASE PRESENTATION: An 87-year-old female with a superotemporal Ahmed valve in the right eye presented with increased "tearing" over the past year, with concern for repeat tube exposure versus normal secretion from the lacrimal gland ductules. Difficulty in differentiation was further increased due to a regional conjunctival pedicled flap for previous tube exposure. Intra-operatively, trypan blue was injected into the anterior chamber of the right eye. The dye was visualized to track along the tube in the direction of the plate, and brisk flow was then observed at the conjunctival area of ambiguity. This confirmed that fluid leakage was due to a glaucoma drainage device-associated conjunctival fistula. The plate and tube were subsequently removed.

CONCLUSIONS: Intraocular injection of trypan blue dye was effective in identifying glaucoma drainage device leakage from tube exposure, and specifically allowing clear differentiation from physiologic lacrimal gland flow. This novel technique successfully differentiated a leaking conjunctival fistula requiring treatment from a benign physiologic finding, in a case where topical fluorescein testing was not sufficient.