title: Corneal hysteresis as a risk factor for glaucoma progression: a prospective longitudinal study.
abstract: OBJECTIVE
  To evaluate the role of corneal hysteresis (CH) as a risk factor for the rate of visual field progression in a cohort of patients with glaucoma followed prospectively over time.
  
  
  METHODS
  Prospective observational cohort study.
  
  
  METHODS
  The study group included 114 eyes of 68 patients with glaucoma followed for an average of 4.0 ± 1.1 years. Visual fields were obtained with standard automated perimetry. Included eyes had a median number of 7 (range, 5-12) tests during follow-up.
  
  
  METHODS
  The CH measurements were acquired at baseline using the Ocular Response Analyzer (Reichert Instruments, Depew, NY). Evaluation of rates of visual field change during follow-up was performed using the visual field index (VFI). Linear mixed models were used to investigate the relationship between rates of visual field loss and baseline CH, baseline intraocular pressure (IOP), and central corneal thickness (CCT), while adjusting for potentially confounding factors. An interaction term between IOP and CH was included in the model to investigate whether the effect of IOP on rates of progression depended on the level of CH.
  
  
  METHODS
  Effects of CH, IOP, and CCT on rates of VFI loss over time.
  
  
  RESULTS
  The CH had a significant effect on rates of visual field progression over time. In the univariable model including only CH as a predictive factor along with time and their interaction, each 1 mmHg lower CH was associated with a 0.25%/year faster rate of VFI decline over time (P<0.001). The multivariable model showed that the effect of IOP on rates of progression depended on CH. Eyes with high IOP and low CH were at increased risk for having fast rates of disease progression. The CH explained a larger proportion of the variation in slopes of VFI change than CCT (17.4% vs. 5.2%, respectively).
  
  
  CONCLUSIONS
  The CH measurements were significantly associated with risk of glaucoma progression. Eyes with lower CH had faster rates of visual field loss than those with higher CH. The prospective longitudinal design of this study supports the role of CH as an important factor to be considered in the assessment of the risk of progression in patients with glaucoma.
  
  
  BACKGROUND
  Proprietary or commercial disclosure may be found after the references.
authors: Hamilton Glaucoma Center and Department of Ophthalmology, University of California, San Diego, California, USA. fmedeiros@glaucoma.ucsd.edu
authors: Felipe A
authors: FA
authors: Medeiros
authors: Daniel
authors: D
authors: Meira-Freitas
authors: Renato
authors: R
authors: Lisboa
authors: Tung-Mei
authors: TM
authors: Kuang
authors: Linda M
authors: LM
authors: Zangwill
authors: Robert N
authors: RN
authors: Weinreb
mesh_terms: D000368:Aged; D015331:Cohort Studies; D003315:Cornea / Q000503:physiopathology; D003316:Corneal Diseases / Q000175:diagnosis* / Q000503:physiopathology; D018450:Disease Progression; D004547:Elastic Tissue / Q000503:physiopathology; D005260:Female; D005500:Follow-Up Studies; D005901:Glaucoma / Q000175:diagnosis* / Q000503:physiopathology; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D014065:Tonometry, Ocular; D014786:Vision Disorders / Q000175:diagnosis* / Q000503:physiopathology; D058609:Visual Field Tests; D014794:Visual Fields
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