A recent study published in Scientific Reports utilized data from the Intelligent Research in Sight (IRIS) Registry to describe the real-world incidence and maintenance of clinically meaningful intraocular pressure (IOP) reduction following standalone phacoemulsification in eyes with suspected or confirmed glaucoma.
Give me some background.
The American Academy of Ophthalmology’s (AAO’s) IRIS Registry is a de-identified clinical database that contains data from almost 500 million patient visits from over 78 million unique patients.
Previous studies have suggested that standalone phacoemulsification reduces IOP for eyes both with and without glaucoma.
- Why: Changes from lens removal may deepen the anatomic angle, which could increase aqueous outflow by expanding the trabecular meshwork, lumen of Schlemm’s canal, and collapsed aqueous valves.
Bring it back to the study.
Consequently, researchers sought to leverage the size of the IRIS Registry to evaluate predictors of a clinically meaningful IOP response and the survival of said IOP response for eyes with glaucoma or pre-glaucoma.
Now talk about the study.
In this retrospective cohort study, investigators included 667,987 eyes in the IRIS Registry with suspected or confirmed glaucoma from January 1, 2013 to September 30, 2019.
Clinically meaningful IOP responses were defined as a ≥20% IOP reduction in daily mean IOP from baseline measured at two consecutive postoperative visits.
- Conversely: If a responder no longer maintained a ≥20% IOP reduction, they were considered a failure.
Findings?
The estimated IOP responder rate was 41.3%, as determined by Kaplan-Meier analysis, and 50% of IOP responders failed at a median time of 14.3 months.
Multivariate analyses demonstrated relationships between IOP response and:
- For every 3 mmHg increase in baseline IOP (hazard ratio [HR] 1.48, 95% confidence interval [CI] 1.48-1.49, P<0.0001)
- Age (HR 1.14, 95% CI 1.13-1.14, per 10 years, P < 0.0001)
- Male sex (HR 1.13, 95% CI 1.12-1.15, P < 0.0001)
- Prostaglandin analog (HR 0.88, 95% CI 0.87-0.90, P < 0.0001)
- Rho-kinase inhibitor use (HR 1.50, 95% CI 1.32-1.70, P = 0.01)
What factors were associated with failed IOP responses?
Additional multivariate analyses indicated relationships between failed IOP response and:
- For every 3 mmHg increase in baseline IOP (HR 0.75, 0.75-0.76, per 3 mmHg, P < 0.0001)
- Nitric oxide donating prostaglandin use (HR 1.78, 1.46-2.18, P < 0.0001)
- Rho-kinase inhibitor use (HR 1.73, 1.43-2.09, P < 0.0001)
Anything else?
With glaucoma suspect as a reference, diagnoses of primary angle-closure suspect (PACS), pseudoexfoliative glaucoma, and primary angle-closure glaucoma (PACG) were more likely to have an IOP response.
- Meanwhile: Patients with normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG) were less likely to have an IOP response.
Expert opinion?
Takeaways from the study highlighted by the authors included:
- Eyes that were aphakic after cataract surgery were less likely to have an IOP response.
- The causative mechanism attributed to age likely involves more than lens density
- Why: Cataract diagnosis, such as total or mature cataract, was not an independent predictor of IOP response.
- Unsurprisingly, nearly all glaucoma diagnoses had greater odds of IOP response failure compared to glaucoma suspect eyes.
- The exception to this was PACS.
Limitations?
These included:
- The retrospective design of the study.
- History of prior filtering surgery was not considered in the exclusion criteria.
- Eyes with combined procedures, such as microinvasive glaucoma surgery (MIGS) were excluded from the study, which may have introduced bias.
- Data from clinical visits with providers who did not participate in the IRIS Registry were not available for analysis.
- IOP and visual acuity (VA) were obtained with variable methods.
- The sample size dropped significantly after 4 months.
Take home.
These findings suggest that physicians could counsel glaucoma patients with the above-mentioned risk factors on whether to anticipate an IOP response and its expected duration after standalone phacoemulsification.
This information may help guide surgical planning to better predict which eyes with glaucoma or pre-glaucoma may or may not have a clinically meaningful and sustained IOP reduction after cataract surgery.
Next steps?
Due to its precision and data volume, the IRIS Registry could be used to train predictive models that could enhance personalized medicine and aid in the decision-making process.