Findings from a recent study published in Ophthalmology Glaucoma identified clinical and demographic predictors of intraocular pressure (IOP)-lowering success following goniotomy using the American Academy of Ophthalmology (AAO) Intelligent Research in Sight (IRIS) Registry.
Give me some background.
Goniotomy is one of the fastest-growing minimally invasive glaucoma surgeries (MIGS) performed by glaucoma specialists and comprehensive ophthalmologists alike in recent years.
The procedure involves excision and/or incision of the trabecular meshwork (TM) to increase aqueous outflow and is generally considered to be a safe procedure with a low barrier to entry as a combined procedure at the time of cataract surgery or as a standalone intervention to reduce IOP.
The study authors noted that while goniotomy is widely performed, long-term real-world analysis of factors associated with goniotomy outcomes remains limited.
As such: Investigators sought to elucidate the factors that influence goniotomy success to help inform surgeons on how to stratify patients in preoperative surgical planning and identify those most likely to respond to this MIGS procedure.
Now talk about the study.
In this retrospective clinical cohort study, investigators included adults who underwent goniotomy between 2013 and 2022 in the IRIS Registry.
The research team evaluated the predictors of short-term surgical success and long-term failure, defined as:
- Short-term success: Between Months 1-6 postoperatively, the eye met the following criteria for at least two consecutive visits after the first postop month:
- IOP ≤21 mmHg
- ≥20% reduction from baseline
- No hypotony (IOP <6 mmHg)
- No additional glaucoma surgery
- Long-term failure: Recorded at the first visit, the aforementioned success criteria were no longer met.
Note: Medication data was excluded from this study.
Plus: Mean IOP over 36 months was compared across glaucoma subtypes and disease severity.
Findings?
Among 48,098 eyes (median age at surgery: 73 years, 55% female patients), 52% achieved short-term success by 6 months.
At 36 months postoperatively, mean IOP decreased from baseline 16.8 mmHg to 15.06 mmHg (10.4% reduction) after phaco-goniotomy (n=31,861) and from 21.28 mmHg to 15.26 mmHg (28.3% reduction) after standalone goniotomy (n=3,776).
Which factors predicted successful or poor outcomes?
The following parameters were independently associated with higher odds of short-term success and lower risk of long-term failure (all P<0.05):
- Higher baseline IOP
- Older age
- Male sex
- Severe glaucoma
- Concurrent cataract surgery
- Pseudoexfoliation glaucoma (PXG)
- Low-tension glaucoma (LTG)
Conversely: Postoperative pilocarpine use (assumed to be applicable to the surgical eye) conferred greater odds of short-term success and greater odds of long-term failure.
Moreover: Black race was a risk factor for failure after 6 months, although other social determinants of health that could underlie this association were not examined.
Expert opinion?
The study authors noted that PXG and LTG being associated with greater odds of success relative to POAG may have been explained by:
- PXG: May respond well to TM excision surgery as it targets the disease at the proximal drainage system, where pseudoexfoliative material clogs the meshwork
- LTG: Within LTG cases, those with higher baseline IOP were more likely to succeed, whereas in cases with the same baseline IOP, those with LTG were more likely to succeed than those with POAG.
Regarding postoperative pilocarpine use, the study authors added that while pilocarpine could theoretically enhance the effect of gonitomy in improving outflow and reducing hyphema-associated IOP spike, long-term failure result suggests that there is lack of persistent remodeling effect on the TM after cessation of medication.
Any limitations?
A few to note, including:
- This study differed from previous studies because its definition of surgical success was limited to IOP values due to the lack of medication laterality in the IRIS Registry; thus the effect of goniotomy on medication burden could not be assessed
- The retrospective nature of the study introduced possibilities of selection bias and unmeasured confounders, such as medication burden, angle anatomy, or diagnostic information, such as imaging data
- Surgical variables, including the device used to perform or the extent of goniotomy, were unavailable
- Concurrent canaloplasty cases were also likely to be grossly underrepresented due to surgeon coding preferences and billing restrictions for the combined procedure
- Follow-up duration varied by patient and may have influenced success detection, although they performed sensitivity analyses to account for this.
- The lack of standardization of postoperative appointments and resulting scarcity of follow-up appointments required a binarization of short-term success data for a more accurate representation of this period
Take home.
These findings suggest that several demographic and clinical factors, including higher baseline IOP, more severe glaucoma, PXG and LTG diagnoses, were predictive of goniotomy success.
Consequently: Goniotomy may benefit patient groups not traditionally prioritized for MIGS.
Although at least half of cases achieved IOP reduction at 6 months, a substantial proportion of eyes ultimately experienced failure by two to three years—highlighting the need for ongoing surveillance and individualized treatment plans.