A recent study published in Investigative Ophthalmology and Visual Science detailed long-term risk factors associated with visual field (VF) progression in eyes with primary angle-closure disease (PACD).
Give me some background.
As an appositional or synechial closure of the anterior chamber angle, PACD is the predominant subtype of glaucoma in the Chinese population—significantly contributing to low vision and blindness within this demographic.
PACD encompasses a spectrum of conditions, including:
- Primary angle-closure suspect (PACS)
- Primary angle-closure (PAC)
- Primary angle-closure glaucoma (PACG)
While several studies have identified risk factors associated with PACD progression, these investigations typically feature short follow-up periods.
Enter: The CUPAL study
The Chinese University of Hong Kong (CUHK) PACG Longitudinal (CUPAL) study is an ongoing, prospective, observational cohort study aimed at investigating the risk factors influencing disease progression in PACD patients.
Consequently: Investigators sought to elucidate long-term risk factors to aid in developing effective treatment strategies and understanding the enduring effects of PACD management.
Now talk about the study.
The research team included 129 PACD eyes that had at least 10 years of follow-up data.
Patients underwent regular evaluation for PACD progression, such as:
- Intraocular pressure (IOP) measurements every 3 months with Goldmann applanation tonometry
- VF testing occurred every 6 months using the 24-2 pattern standard on the Humphrey Field Analyzer
- Initial IOP fluctuation and initial VF index (VFI) slope were calculated based on the first-year follow-up data
Findings?
In total: 40 out of 129 eyes with PACD (31.0%) developed VF progression, with the following breakdown per type:
- PACS eyes: 2 out of 11 (18.2%)
- PAC eyes: 9 out of 52 (17.3%)
- PACG eyes: 29 out of 66 (43.9%)
The two clinical features associated with VF progression in PACG eyes were:
- Higher IOP fluctuation (hazard ratio [HR]: 1.59, 95% confidence interval [CI]: 1.2-2.25)
- Steeper initial VFI slope (HR: 3.33, 95% CI: 2.05-5.40)
Meanwhile: In PACS / PAC eyes only a steeper initial VFI slope (HR: 4.85. 95% CI:1.63-14.45) was associated with VF progression.
Limitations?
These included:
- The study was based on a single site, potentially introducing selection bias and limiting the generalizability of the findings to other clinical settings
- All patients in the study received standardized treatments during follow-up, which may have introduced bias in progression analysis and first-year parameter estimates
- All PACD patients were treated in real-world clinic settings, so the treatment efficacy could have varied between different treatment options
- Cataract and its severity can cause generalized sensitivity reduction on VF testing, potentially confounding the assessment of glaucomatous progression as well as improvements in VF indices by removing the media opacity
Expert opinion?
Based on their findings, the study authors provided key insights into PACD management based on the results of the study, including:
- In PACG, IOP spikes and fluctuations may disproportionately damage the optic nerve due to anatomical constraints (e.g., shallow anterior chamber, crowded angle)
- As IOP levels remained in the normal range for the PACS/PAC group, it is understandable that no associations were found with IOP fluctuation
- This suggests that IOP-lowering intervention may not be the primary intervention strategy to prevent VF progression in PAC and PACS patients
- PACD eyes with a steeper initial VFI slope (< -1.0% / year) were a “high-risk group” for VF progression that required more intensive monitoring and possibly more intensive treatment.
Anything else?
An association between longer axial length (AL) and a higher risk of VF deterioration in PACG was reported.
Further: This was consistent with previous studies that have uncovered that the co-existence of myopia and PACG was common among people younger than 40 years old, and more than half of PACG patients were myopic.
- Why: One possible hypothesis is accommodation-induced IOP fluctuations in myopia, which may increase the vulnerability of myopic eyes to IOP fluctuation, and lead to AL elongation in the sagittal direction.
- Note: With the increasing global prevalence of myopia, it is worthwhile to consider myopia in PACD.
Take home.
These findings emphasize the importance of monitoring IOP fluctuation in PACG eyes and initial VFI slope in PACD eyes, supporting the implementation of tailored management approaches based on disease severity and refractive status.