Diurnal IOP fluctuation: not an independent risk factor for glaucomatous visual field loss in high-risk ocular hypertension

Purpose: To establish whether intraocular pressure (IOP) fluctuations contribute to the risk of developing glaucoma in patients with high-risk ocular hypertension. Methods: Ninety patients included in the Malmo Ocular Hypertension Study were examined every 3 months with office-hours diurnal tension curves and computerised perimetry. Patients were followed up prospectively for 10 years or until glaucomatous visual field loss could be demonstrated. Poststudy data were included in the analyses, extending maximum follow-up to 17 years. Results: After 17 years, 37 patients had developed glaucomatous visual field defects. When applying univariate Cox regression analyses, mean IOP of all measurements during the prospective part of the study was a significant risk factor for developing glaucoma (95% confidence interval [CI] 1.08 - 1.39), while IOP fluctuations were almost significant ( 95% CI 0.98 - 1.93). When separating effects of mean IOP level and mean IOP fluctuation using Cox multiple regression analysis, only IOP level came out as significant ( 95% CI 1.09 - 1.38), and IOP fluctuations did not contribute to the risk ( 95% CI 0.80 - 1.60). IOP fluctuation depended linearly on IOP level ( p< 0.0001), i.e. IOP fluctuation was larger in eyes with higher IOP levels. Conclusion: IOP fluctuations were not an independent risk factor for the incidence of glaucomatous visual field loss in subjects with ocular hypertension.