IOP variability and risk for glaucoma development in patients with ocular hypertension

Abstract

Abstract: : Purpose: To study whether IOP variability contributes to the risk of developing glaucoma in patients with high–risk ocular hypertension. Methods: Ninety patients included in the Malmö ocular hypertension study were examined every 3 months with office hour diurnal tension curves and computerized perimetry. Patients were followed prospectively for 10 years or until glaucomatous visual field loss could be demonstrated. Perimetric post–study data was included in the analysis, extending maximum follow–up to 17 years. Results: After 17 years 37 patients had developed glaucomatous visual field defects. Univariate Cox regression analyses showed that mean IOP measured during the prospective part of the study was a highly significant risk factor for developing glaucoma, while IOP variation was almost significant. The risk increased with 22% for each mmHg of increase in mean follow–up IOP (p=0.013), while each mmHg variation measured as the mean of the range of all diurnal IOP curves increased the risk 34% (p=0.063). However, when combining mean IOP level and mean IOP variation in multivariate Cox regression analysis, only IOP level came out as significant (p=0.005), and IOP variation did not contribute to the risk (p=0.40). IOP variability depended strongly and linearly on IOP level (p<0.0001), i.e. IOP variability was larger in eyes with higher IOP level. Conclusion: Mean IOP was a very strong risk factor for glaucoma development in these patients with high–risk ocular hypertension, while IOP variability was not an independent risk factor.

Keywords: intraocular pressure