This patient’s primary concern is visual improvement rather than reducing glaucoma medications, although she is anticoagulated and not likely to be able to discontinue the topical medication therapy before surgery. I do not know the patient’s baseline or target IOP; however, with stable visual field testing, I can assume that the current level of 15 to 16 mm Hg is adequate, even with thin central corneas.
The lowest risk procedure would be cataract extraction alone with possible selective laser trabeculoplasty in the future, if necessary. With this level of preoperative IOP, cataract extraction alone is not likely to significantly lower the IOP, although the procedure might allow for discontinuation of 1 or both medications.
My preference would be endocyclophotocoagulation (ECP) in combination with cataract extraction, performed at a slightly higher risk than cataract extraction alone, but with a greater likelihood of maintaining IOP and decreasing the use of both glaucoma medications. Alternatively, transscleral micropulse cyclophotocoagulation can be performed with a similar expectation, although it might be less predictable.
The next procedure on the risk spectrum would be trabecular microbypass stent placement, which might involve some risk for reflux of blood from Schlemm canal but with minimum bleeding, unless a problem is encountered with the stent and iris root vessels. Ab interno canaloplasty has a similar risk for blood reflux from the entry point into Schlemm canal. Again, the patient can expect the same IOP as before the surgery, although she might be able to reduce the amount of the glaucoma medications.
Trabecular removal procedures are at the next higher risk for bleeding because of Schlemm canal blood reflux, although this usually clears within 1 week. However, the patient might have a longer visual recovery and a higher IOP because of microhyphema or hyphema. In my experience, removal of trabecular meshwork with ablation causes less bleeding than removal with a cutting dual blade. Performing a trabeculotomy over 360 degrees has the highest bleeding risk in this category.
Because of the risk for bleeding in the suprachoroidal space, I would avoid placement of a shunt device in this region. I would also avoid transconjunctival filtration surgeries, such as placement of a gel stent, trabeculectomy, or placement of an aqueous tube shunt, because of the higher risk for bleeding and because the patient does not require a more aggressive glaucoma procedure.
In summary, this is a patient with moderate visual field loss and thin corneas, but apparently with adequately maintained IOP (with stable visual fields), whose main desire is visual improvement rather than IOP lowering or reducing glaucoma medications. This patient’s main hurdle is the necessity of anticoagulant therapy and the risk for bleeding during or after surgery. My preference would be to perform combined cataract extraction with ECP because this confers minimum risk and reasonable reward. If the patient could stop anticoagulative therapy, I would consider trabecular microbypass or trabecular removal, although both have a small risk for reflux of blood from Schlemm canal (microbypass less than removal) that might occur after recovery from surgery when the anticoagulant has been resumed. In the end, however, the patient’s preference will prevail.