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Editors Selection IGR 16-4
Prognostic factors: IOP variability and visual field progression
Comment by Gustavo de Moraes on:
116979 Relationship between Intraocular Pressure Fluctuation and Visual Field Progression Rates in the United Kingdom Glaucoma Treatment Study, Rabiolo A; Montesano G; Crabb DP et al., Ophthalmology, 2024; 131: 902-913
Rabiolo et al. investigated the relationship between intraocular pressure (IOP) fluctuation and visual field (VF) progression in the United Kingdom Glaucoma Treatment Study (UKGTS). The study included 430 participants with at least five VF tests (213 placebo, 217 treatment). In the placebo group, the authors found that a latent variable (PC1) that captures IOP peak and mean, among others, as well Pascal ocular pulse amplitude (OPA) were associated with faster rates of VF progression. In the treatment group, only PC1 had a significant association. However, diurnal or long-term IOP fluctuations were not associated with progression in either group. The study concluded that there was no evidence to support that either diurnal or long-term IOP fluctuation, as measured in clinical practice, are independent factors for glaucoma progression. Other aspects of IOP, including mean IOP and peak IOP, may be more informative.
The paper presents data of a well-conducted randomized trial which helped mitigate the effects of treatment escalation on the investigated relationship between IOP and progression. This was not done as systematically in previous, related studies, therefore limiting the interpretation of their results. The authors meticulously evaluated IOP fluctuation across various timeframes, including short-term, office hours (diurnal fluctuation), and long-term (between-visit variation). This approach provides a thorough understanding of IOP fluctuation dynamics. They also employed principal component analysis (PCA) to address the issue of multicollinearity among IOP-related metrics, which was largely overlooked in previous studies. This approach ensured that the statistical analysis was not compromised by the high correlation between variables.
The study did not include nighttime/ early morning IOP measurements, which could provide valuable insights into the relationship between nocturnal IOP fluctuations and glaucoma progression
Furthermore, the only relevant limitation was that the study cohort primarily consisted of treatment-naïve patients with early glaucomatous damage, mainly of European descent. This limits the generalizability of the findings to other populations, particularly those with advanced glaucoma or different racial backgrounds. Although not of major concern, the study did not include nighttime/ early morning IOP measurements, which could provide valuable insights into the relationship between nocturnal IOP fluctuations and glaucoma progression. Of course, this would have required a much more complex study design and was not the focus of the trial.
Overall, the study by Rabiolo et al. is a well-conducted investigation that contributes significantly to our understanding of the relationship between IOP fluctuation and glaucoma progression. The authors should be commended for their rigorous methodology, comprehensive assessment of IOP fluctuation, and efforts to minimize confounding factors.
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