Intraocular Pressure Control Predicts Retinal Nerve Fiber Layer Thinning in Primary Angle Closure Disease: The CUPAL Study.

Purpose: To determine the relationship of intraocular pressure (IOP) control with subsequent retinal nerve fiber layer (RNFL) thinning in patients with primary angle closure disease (PACD).
Design: Prospective cohort study.
Methods: The study monitored 517 treated PACD eyes from 280 Chinese patients at least 24 months. IOP was measured every 3 months using Goldmann applanation tonometry, and RNFLs were measured by spectral-domain optical coherence tomography (Spectralis, Heidelberg Engineering) every 6 months. IOP mean and fluctuation were calculated as the average and the coefficient of variation of IOP measurements during the first 18 months of the study period. The relationship between IOP and subsequent RNFL changes over time were examined using multivariable linear mixed models. Intraclass correlations at the patient and eye levels were also controlled using nested random intercepts in the models.
Results: IOP mean (β = -1.20 µm/y per 1 mm Hg, P < .001) and IOP fluctuation (β = -3.10 µm/y per 10% unit change in the coefficient of variation, P < .001) were independently negatively associated with subsequent progressive global RNFL changes, after adjustment for age, sex, and baseline RNFL thickness. In the sectoral analysis, both higher mean IOP and IOP fluctuation predicted progressive RNFL thinning in the inferotemporal, superotemporal, superonasal, and temporal sectors in the order of strength of association. In the subgroup analysis by disease category, IOP fluctuation showed greater association with global RNFL thinning in eyes with primary angle closure glaucoma (P = .010) than in eyes without glaucomatous changes (P = .07).
Conclusions: In treated PACD eyes, large IOP fluctuation is an independent predictor for subsequent progressive RNFL thinning in addition to high mean IOP during follow-up.
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