title: Evaluating relaxed ciliary muscle tone in presbyopic eyes.
abstract: OBJECTIVE
  Studies of age-related changes in ciliary muscle (CM) morphology and contractility have variously reported that CM weakens or strengthens with age. In response, the aim of this study was to evaluate relaxed CM tone in vivo in pre-presbyopic and presbyopic patients using a predictor value (PCM).
  
  
  METHODS
  Two groups of eyes-40 eyes of 40 healthy volunteers with a mean age of 28.1 ± 5.8 years and 40 eyes of 40 healthy volunteers with a mean age of 56.6 ± 7.3 years-formed the sample for this prospective, observational cross-sectional study. Used to evaluate relaxed CM tone, PCMwas calculated as the difference between the change in mean anterior chamber depth (ACD) and lens thickness (LT) before and after cycloplegia, as measured with swept-source optical biometry.
  
  
  RESULTS
  The PCMfor relaxed CM tone was 0.04 ± 0.04 mm in pre-presbyopic participants, 0.06 ± 0.03 mm in presbyopic ones, and significantly greater in presbyopic patients (p = .018).
  
  
  CONCLUSIONS
  The statistical significance of PCMbetween pre-presbyopic and presbyopic eyes might not signify clinical significance, since the difference was close to the repeatability limits for swept-source optical biometry. When relaxed, CM tone does not diminish with presbyopia according to changes in anterior chamber parameters due to cycloplegia.
authors.affiliation: Department of Ophthalmology, Mugla Sitki Kocman University, Training and Research Hospital, Mugla, 48000, Turkey. erhanozyol@mynet.com.
authors.forename: Erhan
authors.initials: E
authors.lastname: Özyol
authors.affiliation: Department of Ophthalmology, Mugla Sitki Kocman University, Faculty of Medicine, Mugla, Turkey.
authors.forename: Pelin
authors.initials: P
authors.lastname: Özyol
mesh_terms: D000065:Accommodation, Ocular / Q000502:physiology*; D000328:Adult; D002924:Ciliary Body / Q000473:pathology / Q000503:physiopathology*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009129:Muscle Tonus / Q000502:physiology*; D011305:Presbyopia / Q000175:diagnosis / Q000503:physiopathology*; D011446:Prospective Studies; D041623:Tomography, Optical Coherence; D055815:Young Adult
keywords: Ciliary muscle; Cycloplegia; Presbyopia