title: Evaluation of Postural Control in Patients with Glaucoma Using a Virtual Reality Environment.
abstract: OBJECTIVE
  To evaluate postural control using a dynamic virtual reality environment and the relationship between postural metrics and history of falls in patients with glaucoma.
  
  
  METHODS
  Cross-sectional study.
  
  
  METHODS
  The study involved 42 patients with glaucoma with repeatable visual field defects on standard automated perimetry (SAP) and 38 control healthy subjects.
  
  
  METHODS
  Patients underwent evaluation of postural stability by a force platform during presentation of static and dynamic visual stimuli on stereoscopic head-mounted goggles. The dynamic visual stimuli presented rotational and translational ecologically valid peripheral background perturbations. Postural stability was also tested in a completely dark field to assess somatosensory and vestibular contributions to postural control. History of falls was evaluated by a standard questionnaire.
  
  
  METHODS
  Torque moments around the center of foot pressure on the force platform were measured, and the standard deviations of the torque moments (STD) were calculated as a measurement of postural stability and reported in Newton meters (Nm). The association with history of falls was investigated using Poisson regression models. Age, gender, body mass index, severity of visual field defect, best-corrected visual acuity, and STD on dark field condition were included as confounding factors.
  
  
  RESULTS
  Patients with glaucoma had larger overall STD than controls during both translational (5.12 ± 2.39 Nm vs. 3.85 ± 1.82 Nm, respectively; P = 0.005) and rotational stimuli (5.60 ± 3.82 Nm vs. 3.93 ± 2.07 Nm, respectively; P = 0.022). Postural metrics obtained during dynamic visual stimuli performed better in explaining history of falls compared with those obtained in static and dark field condition. In the multivariable model, STD values in the mediolateral direction during translational stimulus were significantly associated with a history of falls in patients with glaucoma (incidence rate ratio, 1.85; 95% confidence interval, 1.30-2.63; P = 0.001).
  
  
  CONCLUSIONS
  The study presented and validated a novel paradigm for evaluation of balance control in patients with glaucoma on the basis of the assessment of postural reactivity to dynamic visual stimuli using a virtual reality environment. The newly developed metrics were associated with a history of falls and may help to provide a better understanding of balance control in patients with glaucoma.
authors.affiliation: Visual Performance Laboratory, Department of Ophthalmology, University of California, San Diego, La Jolla, California; Department of Ophthalmology and Otorhinolaryngology, Federal University of Minas Gerais, Belo Horizonte, Brazil.
authors.forename: Alberto
authors.initials: A
authors.lastname: Diniz-Filho
authors.affiliation: Visual Performance Laboratory, Department of Ophthalmology, University of California, San Diego, La Jolla, California; Department of Mechanical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Erwin R
authors.initials: ER
authors.lastname: Boer
authors.affiliation: Visual Performance Laboratory, Department of Ophthalmology, University of California, San Diego, La Jolla, California; Department of Ophthalmology, Federal University of São Paulo, São Paulo, Brazil.
authors.forename: Carolina P B
authors.initials: CP
authors.lastname: Gracitelli
authors.affiliation: Visual Performance Laboratory, Department of Ophthalmology, University of California, San Diego, La Jolla, California; Department of Ophthalmology, University of Campinas, Campinas, Brazil.
authors.forename: Ricardo Y
authors.initials: RY
authors.lastname: Abe
authors.affiliation: Department of Mechanical Engineering, Delft University of Technology, Delft, The Netherlands.
authors.forename: Nienke
authors.initials: N
authors.lastname: van Driel
authors.affiliation: Visual Performance Laboratory, Department of Ophthalmology, University of California, San Diego, La Jolla, California.
authors.forename: Zhiyong
authors.initials: Z
authors.lastname: Yang
authors.affiliation: Visual Performance Laboratory, Department of Ophthalmology, University of California, San Diego, La Jolla, California. Electronic address: fmedeiros@ucsd.edu.
authors.forename: Felipe A
authors.initials: FA
authors.lastname: Medeiros
mesh_terms: D000058:Accidental Falls; D000368:Aged; D000369:Aged, 80 and over; D003198:Computer Simulation; D003430:Cross-Sectional Studies; D005260:Female; D005500:Follow-Up Studies; D005902:Glaucoma, Open-Angle / Q000175:diagnosis / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D004856:Postural Balance / Q000502:physiology*; D011187:Posture / Q000502:physiology*; D011446:Prospective Studies; D011795:Surveys and Questionnaires; D014584:User-Computer Interface; D014792:Visual Acuity / Q000502:physiology; D058609:Visual Field Tests; D014794:Visual Fields / Q000502:physiology