Findings from a study published in International Ophthalmology assessed the long-term outcomes of canaloplasty (CP) and phaco-canaloplasty (PCP) to treat open-angle glaucoma (OAG) and evaluate the predictive factors associated with surgical outcomes.
Give me some background.
Ab-externo CP is a non-filtering, non-penetrating surgical procedure that reduces intraocular pressure (IOP) by increasing the humor aqueous flow through the physiological pathway.
Depending on the patient's risk factors, surgeons may opt to treat concomitant cataract and glaucoma with a combined procedure (i.e., PCP) to reduce the need for additional surgery and follow-up visits.
- However: The study authors noted that there is a dearth of research on whether PCP is more effective than CP alone in reducing IOP and glaucoma medications.
Talk about the study.
In this 48-month retrospective study, investigators analyzed the outcomes from 133 OAG eyes treated with CP and 57 OAG eyes treated with PCP—all performed by a single surgeon.
Surgical success was defined according to six criteria:
- Achieving a target IOP ≤ 21, 18, or 15 mmHg on glaucoma medications
- Considered a qualified success
- Achieving said IOP without any further treatment (including laser therapy or surgery)
- Considered a complete success
Surgical complications in the early postoperative period were compared between CP and PCP.
Findings?
Three key results included:
- CP and PCP significantly reduced postoperative IOP and the number of glaucoma medications (p= 0.001 for both)
- CP demonstrated efficacy (i.e., a steady 30% reduction of IOP) for up to 48 months and PCP for up to 42 months
- A preoperative number of >4 glaucoma medications predicted surgical failure.
Tell me more about phaco-canaloplasty.
PCP showed higher rates of cumulative surgical success over CP, but only for target IOP ≤21 and ≤18 mmHg (p=0.018 and p=0.011, respectively).
Further, PCP was associated with a higher rate of IOP peaks in the first month compared with canaloplasty (40.4% vs. 12.7%, p=0.000)—emphasizing the need for a closer follow-up during the early postoperative period.
Limitations
The main limitations of the study were its retrospective design and the inclusion of patients at various stages of glaucomatous disease with different target IOPs.
- Why: This may have introduced bias in assessing the rate of surgical success.
Expert opinion?
The study authors explained that the elevated IOP the first days after surgery in patients who underwent PCP was likely secondary to:
- The retention of viscoelastic material in the anterior chamber
- A hindered Schlemm’s canal that prevented aqueous humor outflow
- Higher levels of intraocular inflammation
Take home.
These findings indicated that CP and PCP demonstrated long-term efficacy (48 and 42 months, respectively) for holding a steady 30% reduction of IOP in patients with OAG.
In addition: PCP showed higher rates of surgical success compared to CP, excluding target IOPs lower than 16 mmHg.
Lastly, the authors concluded that patients on more than four preoperative glaucoma medications may not be good candidates for CP and could benefit from other surgical options.