In simple words: This surgery helps lower eye pressure in people with glaucoma who have had previous eye surgery or injuries. The doctor creates a new drainage channel and removes some tissue to improve fluid flow, and then injects medication to reduce scarring.

This procedure involves creating a fistula and removing a portion of the trabecular meshwork in an eye with scarring from prior surgery or trauma.The procedure is performed ab externo (from outside the eye).Antifibrotic agents are injected to help prevent post-operative scarring and fibrosis. The creation of the fistula improves aqueous humor outflow and reduces intraocular pressure, addressing glaucoma. Due to pre-existing scarring, the procedure presents increased challenges such as potential for increased bleeding and meticulous closure is necessary.

Example 1: A 65-year-old male patient with a history of previous unsuccessful glaucoma surgery presents with elevated intraocular pressure.Code 66172 is used to perform a trabeculectomy ab externo with antifibrotic injection to address the glaucoma and the challenges posed by previous surgical scarring., A 72-year-old female patient experienced trauma to her eye resulting in significant scarring. She develops glaucoma as a consequence. Code 66172 is used to address the glaucoma by creating a fistula and removing scar tissue that obstructs the normal outflow of aqueous humor., A 58-year-old patient underwent previous glaucoma surgery.Due to complications from the previous surgery resulting in scarring and elevated IOP, a revision surgery using code 66172 is performed to relieve pressure and improve drainage.The presence of extensive scar tissue significantly increases the complexity of the revision.

* Preoperative assessment including visual acuity, intraocular pressure measurements, and gonioscopy.* Detailed operative report including the approach (ab externo), the creation of the fistula, the amount of trabecular meshwork removed, and the type and amount of antifibrotic agent used.* Postoperative assessment including visual acuity, intraocular pressure measurements, and examination for complications such as bleeding or infection.* Patient history of previous surgeries, including dates and surgical details.* Medical necessity documentation to justify the procedure.

** This procedure is more complex and potentially riskier in the presence of pre-existing scarring. Careful surgical technique and consideration of potential complications are crucial. Always refer to the most up-to-date CPT and payer guidelines for accurate coding and reimbursement.