Corneal Biomechanics and Visual Field Progression in Eyes with Seemingly Well-Controlled Intraocular Pressure

Purpose: To investigate the incidence and risk factors for glaucomatous visual field progression in eyes with well-controlled intraocular pressure (IOP). Design: Prospective cohort. Participants: A total of 460 eyes of 334 patients with glaucoma under treatment. Methods: Study subjects had a mean follow-up of 4.3 +/- 0.8 years. Patients were classified as well controlled if all IOP measurements were less than 18 mmHg. Rates of visual field progression were calculated using ordinary least-squares linear regression of standard automated perimetry (SAP) mean deviation (MD) values over time. Progression was defined as a significantly negative MD slope (alpha = 0.05). Main Outcome Measures: Rates of SAP MD change; mean and peak IOP, and IOP fluctuation; and corneal biomechanics: corneal hysteresis (CH), central corneal thickness (CCT), and corneal index. Results: Of the 179 eyes with well-controlled IOP, 42 (23.5%) demonstrated visual field progression. There was no significant difference between progressing and stable patients in baseline MD (-6.4 +/- 7.1 decibels [dB] vs. -6.0 +/- 6.2 dB; P = 0.346), mean IOP (11.7 +/- 2.0 mmHg vs. 12.1 +/- 2.3 mmHg; P = 0.405), IOP fluctuation (1.6 +/- 0.6 mmHg vs. 1.6 +/- 0.5 mmHg; P = 0.402), or peak IOP (14.3 +/- 1.9 mmHg vs. 14.6 +/- 2.1 mmHg; P = 0.926). Progressing eyes had significantly lower CH (8.6 +/- 1.3 mmHg vs. 9.4 +/- 1.6 mmHg; P = 0.014) and thinner CCT (515.1 +/- 33.1 mu m vs. 531.1 +/- 42.4 mu m; P = 0.018, respectively) compared with stable eyes. In the multivariate analysis, a 1 standard deviation lower corneal index, a summation of normalized versions of CH and CCT, resulted in a 68% higher risk of progression (odds ratio, 1.68; 95% confidence interval, 1.08-2.62; P = 0.021). Conclusions: Approximately one-quarter of eyes with well-controlled IOP may show visual field progression over time. Thin cornea and low CH are main risk factors. (C) 2019 by the American Academy of Ophthalmology