The risk of cataract and glaucoma, two common ophthalmic conditions, increases with age. Consequently, visually significant cataracts often present as a concomitant issue with glaucoma in older patients. There has been a great deal of discussion regarding whether to surgically address both of these conditions at the same time or to perform two separate surgeries at different times. Furthermore, if the decision to carry out cataract surgery on a patient who also has glaucoma has been made, whether the cataract or glaucoma surgery should be performed first has also been debated.

GOAL OF TRABECULECTOMY

Traditionally, the gold standard for the surgical treatment of patients with open-angle glaucoma (OAG) has been trabeculectomy with the use of antifibrotic therapy. Historically, cataract surgery at the time of trabeculectomy has been the most commonly performed glaucoma-cataract combination procedure. The goal of the trabeculectomy procedure is to create an alternative route for aqueous humor to drain out of the eye and into a subconjunctival reservoir, thus creating a bleb. Unfortunately, despite the fact that trabeculectomy surgery has proven to be very effective in both lowering IOP and halting disease progression, it comes with the risk of immediate or delayed postsurgical complications1-6 such as blebitis, bleb-associated endophthalmitis, and hypotony.7-10 These potentially devastating complications have led many surgeons to shy away from bleb-based surgery and have fueled the interest and popularity in minimally invasive blebless procedures.

CANALOPLASTY TO REDUCE IOP

Amidst the boom in advances in glaucoma surgery, canaloplasty has emerged as an effective and safe way to surgically lower IOP with a much lower risk profile than conventional filtration surgery.11-13 Canaloplasty reduces IOP by reestablishing the natural conventional outflow pathway without forming a bleb. Lewis et al demonstrated a significant reduction of IOP and medication usage via canaloplasty 3 years postoperatively11 with results similar to trabeculectomy.14,15 Canaloplasty lowered IOP from 23.5 mm Hg ±4.5 to 15.5 mm Hg ±3.5 (34%) and decreased the average number of medications taken from 1.9 ±0.8 to 0.9 ±0.9 (53%) 3 years postoperatively.

Combining clear corneal cataract extraction via phacoemulsification with canaloplasty resulted in an even greater decrease in IOP.11 Phacocanaloplasty lowered IOP from 23.5 mm Hg ±5.2 to 13.6 mm Hg ±3.6 (42%) 36 months postoperatively, and the average number of medications dropped from 1.5 ±1.0 to 0.2 ±0.5 (80%). Transient hyphema at a rate of 10.2% was the most commonly occurring complication, but no sustained hypotony or related complications were reported. Although inadvertent blebs occurred in 2.5% of cases, no blebitis or bleb-related complications were reported 3 years after phacocanaloplasy.

Patient selection

Patients with a visually significant cataract may be a stong candidate for phacocanaloplasty if he or she has mild to advanced glaucomatous optic neuropathy. Cataract patients who cannot tolerate topical medical therapy for glaucoma or who are burdened by multiple topical medications are also candidates for the procedure. Individuals who have had a failed prior glaucoma procedure, who anticipate cataract surgery in the near future, or who have a phacomorphic glaucoma component without peripheral anterior synechiae may also be considered for phacocanaloplasty.

SURGICAL PROCEDURE

Typically, anesthesia and akinesia are achieved with a retrobulbar block, although some surgeons perform phacocanaloplasty under topical anesthesia. Clear corneal cataract extraction via phacoemulsification is performed using traditional methods; however, the surgeon may have to slightly alter his or her surgical technique.

POINTS TO CONSIDER

The placement of the paracentesis is important when glaucoma surgery is expected to follow the initial procedure. The surgeon must position the sideport incision such that it will not intersect the anticipated corneal traction suture needed during canaloplasty. If working on a right eye, a right-handed surgeon may place his or her sideport incision at approximately 10 o'clock and skew the clear corneal incision inferotemporally. Likewise, the same consideration should be given to the surgeon's standard clear corneal temporal incision.

It is important to thoroughly remove the ophthalmic viscosurgical device after cataract surgery to avoid postoperative IOP spikes. If the surgeon considers suturing the clear corneal incision after cataract surgery to maintain anterior chamber stability, it is crucial that the tied suture not transect or lead to a stricture of Schlemm canal (Figure 1).

PERFORMING THE CANALOPLASTY

Once cataract surgery is successfully performed, the canaloplasty procedure can commence. Canaloplasty involves conjunctival exposure to enable a superficial then deep scleral flap creation followed by unroofing Schlemm canal, which is then catheterized (Figure 2). The surgeon uses a microcatheter tipped with an illuminating optical fiber and an ophthalmic viscosurgical device delivery system to canulate and viscodilate Schlemm canal for 360º (Figure 3). Finally, this same catheter is used to introduce a polypropylene suture into Schlemm canal for tension application and canal distension.

When performing canaloplasty, it is important to consider a superonasal approach during the conjunctival fornix-based peritomy, as it leaves the superior and superotemporal conjunctiva undisturbed, should future incisional surgeries be necessary. To identify Schlemm canal, dissect the deep scleral flap anteriorly and look for cross-striations of scleral spur, as these indicate that the dissection is approaching Schlemm canal.

CONCLUSION

Canaloplasty has become an appealing alternative to traditional incisional glaucoma filtering surgery. The procedure is less invasive and blebless, requires no antifibrotics and lowers IOP, and its intra- and postoperative risk profiles are favorable. Furthermore, postoperative care is very similar to that of cataract surgery. Patients are typically placed on topical antibiotics and low-dose topical steroids for several weeks postoperatively. Phacocanaloplasty shows a lower IOP trend than canaloplasty alone. Therefore, combining canaloplasty and phacoemulsification has gained popularity when treating a patient with visually significant cataracts and glaucoma.

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