Question: How should I bill lacrimal probing when performed bilaterally? North Carolina Subscriber Answer: You should report bilateral lacrimal probing with 68810* (Probing of nasolacrimal duct, with or without irrigation) with modifier -50 (Bilateral procedure) appended for Medicare, and modifiers -RT (Right side) and -LT (Left side) on two lines for private payers. This is a unilateral code.