Intraocular pressure and optical coherence tomography concerning visual field outcomes in "green" patients: An observational study

Abstract

This study investigates the relationship between intraocular pressure (IOP), optical coherence tomography (OCT) parameters, and visual field (VF) outcomes in 'Green' patients-those with normal OCT findings but potential VF abnormalities. Understanding this relationship is crucial for improving early detection and management strategies for glaucoma, especially in patients who show functional loss despite normal structural findings on OCT. A cross-sectional study was conducted at Taipei City Hospital, Renai Branch, Taiwan, from July 1, 2015, to July 1, 2023. Participants were referred for suspected glaucoma and included based on normal OCT parameters ('green' coding) and completed VF tests. Patients with any ocular disease that could confound results were excluded. Logistic regression models were used to assess relationships between IOP, OCT parameters (rim area, disc area, retinal nerve fiber layer thickness, cup-to-disc ratios, and cup volume), and VF outcomes. Age, sex, and IOP status (normal or ocular hypertension) were also included in the analysis. All data were analyzed using Statistical Package for the Social Sciences version 23.0. Larger disc area was a significant predictor of VF abnormalities, with an adjusted OR of 3.72 (95% confidence interval [CI], 1.14-12.15). Neither normal IOP nor ocular hypertension significantly predicted VF loss (adjusted OR = 0.89; 95% CI, 0.27-2.96). Female sex was associated with a higher likelihood of VF abnormalities (adjusted OR = 5.68; 95% CI, 1.03-31.25). Other OCT parameters, including retinal nerve fiber layer thickness and cup-to-disc ratios, were not significantly associated with VF outcomes. Disc area plays a critical role in predicting VF abnormalities in "green" patients, suggesting the importance of integrating disc size into screening and monitoring protocols. These findings challenge the reliance on IOP alone for predicting VF loss and support the need for more comprehensive assessments. Future research should explore longitudinal studies to further assess the predictive value of disc area and investigate additional factors, such as vascular and biomechanical influences, that may contribute to VF deterioration in this population.

Figure 1.

Flowchart of the selected patients. OCT = optical coherence tomography.