Authors’ Response to comment on “Outcomes of bent ab interno needle goniectomy with phacoemulsification in moderate to severe primary open-angle glaucoma”

Dear Editor, In the current scenario, most angle-based minimally invasive glaucoma surgeries (MIGS) for glaucoma are combined with phacoemulsification. In patients with angle-closure glaucoma, angle-based MIGS are performed after phacoemulsification, as this procedure deepens the anterior chamber (AC). In these cases, following phacoemulsification and intraocular lens implantation, the pupil is pharmacologically constricted to enhance visualization of the anterior chamber angle, aiding in the MIGS procedure. In open-angle glaucoma, angle-based MIGS can be performed either before or after phacoemulsification.[1] X et al. questioned the pupillary status when angle-based MIGS is performed prior to phacoemulsification.[2] In our recent study, bent ab interno needle goniectomy (BANG) was conducted before phacoemulsification with a dilated pupil.[1] In eyes with open-angle glaucoma, the AC depth is usually adequate and can be further deepened using cohesive viscoelastic, such as Healon GV Pro (1.8% Sodium hyaluronate: Johnson-Johnson Surgical Vision, Inc, Santa Ana, CA, USA) to improve visualization of the AC angle.[3] In these cases, pupillary constriction was not necessary for angle visualization. Further, if we constrict the pupil for angle-based MIGS, it would need to be redilated for phacoemulsification. Inadequate pupil dilation can complicate phacoemulsification and increase the risk of intraoperative complications. As noted by X et al., if hyphema occurs immediately after BANG, irrigation and aspiration should be performed until the hyphema resolves.[2] Additionally, the bottle height of the phacoemulsification machine or intraocular pressure (IOP) level should be increased (depending on the type of phacoemulsification machine used) to further help prevent hyphema. Once resolved, phacoemulsification can proceed as usual. Performing angle-based MIGS prior to phacoemulsification in open-angle glaucoma cases offers two main advantages. First, optimal visualization can be achieved with a clear cornea. If angle-based MIGS is performed after phacoemulsification, corneal edema could cloud the cornes, impeding angle visualization and complicating the MIGS procedure. Second, the use of viscoelastic in a phakic eye can tamponade any bleeding, allowing it to stop sooner. After phacoemulsication, the IOP tends to drop, which increases the risk of bleeding when MIGS is performed due to hypotony. Additionally, post-operative hyphema is more likely, with potential for blood to enter the vitreous cavity and cause prolonged decrease in visual acuity. If MIGS is performed after phacoemulsification, the eye must be closed at higher IOP using either viscoelastic or an air bubble to prevent early post-operative hyphema, which could contribute to the progression of glaucomatous optic neuropathy. The primary disadvantage of performing MIGS before phacoemulsification is the ability to attend the constrict the pupil, as a dilated pupil is necessary for phacoemulsification, posing a small risk of damaging the anterior capsule. Thus, when angle-based MIGS is combined with phacoemulsification in eyes with open-angle glaucoma, it is generally performed before cataract surgery. However, performing MIGS after lens extraction remains a viable option. Financial support and sponsorship: Nil. Conflicts of interest: There are no conflicts of interest.