title: Changes in central corneal thickness over time: the ocular hypertension treatment study.
abstract: OBJECTIVE
  To describe how much change, if any, occurs between central corneal thickness (CCT) measurements performed an average of 3.8 years apart in participants in the Ocular Hypertension Treatment Study (OHTS) and to identify clinical and demographic factors that are associated with changes in CCT, including baseline intraocular pressure, duration and class of ocular hypotensive medication, medical history, and systemic medication.
  
  
  METHODS
  Secondary analysis of data from a randomized clinical trial.
  
  
  METHODS
  Ocular Hypertension Treatment Study participants. Participants who had undergone incisional intraocular or keratorefractive surgery between CCT measurements were excluded.
  
  
  METHODS
  The first CCT measurements were performed starting in 1999, and the second measurements were performed starting in 2002. Measurements were performed by OHTS certified technicians using an ultrasonic pachymeter under a standardized protocol.
  
  
  METHODS
  Central corneal thickness measurement (micrometers).
  
  
  RESULTS
  First and second CCT measurements were available from 73% (1191) of the 1636 OHTS participants randomized. Central corneal thickness decreased a mean rate of -0.74+/-3.5 microm/year between the first and second CCT measurements. The mean medication exposure between first and second CCT measurements in participants originally randomized to observation (n = 595) was 1.1+/-1.6 years, versus 5.0+/-2.7 years in participants originally randomized to medication (n = 596). Central corneal thickness decreased by a mean of 1.0+/-3.4 microm/year among participants originally randomized to observation, compared with 0.5+/-3.5 microm/year among participants originally randomized to medication (P<0.0001). Subgroup analyses suggest that participants treated only with topical prostaglandin analogues (PGAs) between the two CCT measurements had a greater rate of decrease per year than participants treated only with topical beta-blockers.
  
  
  CONCLUSIONS
  The rate of CCT decrease over 3.8 years is comparable to the cross-sectional age differences reported in the OHTS at the first measurement (0.6 microm/year) and comparable to other cross-sectional studies. Use of topical PGAs may be associated with a slightly higher rate of thinning. The modest age- and drug-related rates of thinning observed are unlikely to influence tonometry or clinical decision-making substantially in most clinical situations.
authors: Department of Ophthalmology and Vision Science, University of California, Sacramento, California, USA.
authors: James D
authors: JD
authors: Brandt
authors: Mae O
authors: MO
authors: Gordon
authors: Julia A
authors: JA
authors: Beiser
authors: Shan C
authors: SC
authors: Lin
authors: Monica Y
authors: MY
authors: Alexander
authors: Michael A
authors: MA
authors: Kass
mesh_terms: D000287:Administration, Topical; D000368:Aged; D000959:Antihypertensive Agents / Q000627:therapeutic use*; D001837:Body Weights and Measures; D003315:Cornea / Q000000981:diagnostic imaging / Q000473:pathology*; D005260:Female; D005902:Glaucoma, Open-Angle / Q000175:diagnosis* / Q000517:prevention & control; D006801:Humans; D007429:Intraocular Pressure; D008297:Male; D008875:Middle Aged; D009798:Ocular Hypertension / Q000175:diagnosis / Q000188:drug therapy; D009901:Optic Nerve Diseases / Q000175:diagnosis* / Q000517:prevention & control; D011446:Prospective Studies; D013997:Time Factors; D014463:Ultrasonography; D014786:Vision Disorders / Q000175:diagnosis* / Q000517:prevention & control; D014794:Visual Fields
chemical_list: D000959:Antihypertensive Agents