title: The effect of changes in intraocular pressure on the risk of primary open-angle glaucoma in patients with ocular hypertension: an application of latent class analysis.
abstract: BACKGROUND
  Primary open-angle glaucoma (POAG) is one of the leading causes of blindness in the United States and worldwide. While lowering intraocular pressure (IOP) has been proven to be effective in delaying or preventing the onset of POAG in many large-scale prospective studies, one of the recent hot topics in glaucoma research is the effect of IOP fluctuation (IOP lability) on the risk of developing POAG in treated and untreated subjects.
  
  
  METHODS
  In this paper, we analyzed data from the Ocular Hypertension Treatment Study (OHTS) and the European Glaucoma Prevention Study (EGPS) for subjects who had at least 2 IOP measurements after randomization prior to POAG diagnosis. We assessed the interrelationships among the baseline covariates, the changes of post-randomization IOP over time, and the risk of developing POAG, using a latent class analysis (LCA) which allows us to identify distinct patterns (latent classes) of IOP trajectories.
  
  
  RESULTS
  The IOP change in OHTS was best described by 6 latent classes differentiated primarily by the mean IOP levels during follow-up. Subjects with high post-randomization mean IOP level and/or large variability were more likely to develop POAG. Five baseline factors were found to be significantly predictive of the IOP classification in OHTS: treatment assignment, baseline IOP, gender, race, and history of hypertension. In separate analyses of EGPS, LCA identified different patterns of IOP change from those in OHTS, but confirmed that subjects with high mean level and large variability were at high risk to develop POAG.
  
  
  CONCLUSIONS
  LCA provides a useful tool to assess the impact of post-randomization IOP level and fluctuation on the risk of developing POAG in patients with ocular hypertension. The incorporation of post-randomization IOP can improve the overall predictive ability of the original model that included only baseline risk factors.
authors.affiliation: Division of Biostatistics, Washington University School of Medicine, St, Louis, MO, 63110, USA. feng@wustl.edu
authors.forename: Feng
authors.initials: F
authors.lastname: Gao
authors.forename: J Philip
authors.initials: JP
authors.lastname: Miller
authors.forename: Stefano
authors.initials: S
authors.lastname: Miglior
authors.forename: Julia A
authors.initials: JA
authors.lastname: Beiser
authors.forename: Valter
authors.initials: V
authors.lastname: Torri
authors.forename: Michael A
authors.initials: MA
authors.lastname: Kass
authors.forename: Mae O
authors.initials: MO
authors.lastname: Gordon
mesh_terms: D001766:Blindness; D015331:Cohort Studies; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000209:etiology*; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension; D012307:Risk Factors; D013534:Survival; D014065:Tonometry, Ocular; D014794:Visual Fields