title: Biomechanical evaluation of cornea in patients with ankylosing spondylitis.
abstract: OBJECTIVE
  The aim of this study was to evaluate the corneal biomechanical parameters in patients with ankylosing spondylitis (AS) and to compare them with the healthy subjects.
  
  
  METHODS
  Sixty patients with AS (study group) and 60 healthy subjects (control group) were enrolled in this prospective study. The study group was further classified as active (n:30) and inactive (n:30). After detailed ophthalmological examination including intraocular pressure (IOP) measurement with Goldmann applanation tonometer (IOPGAT), corneal hysteresis (CH), corneal resistance factor (CRF), corneal-compensated IOP (IOPcc), and Goldmann-correlated IOP (IOPg) were measured with the Reichert Ocular Response Analyzer (ORA). Central corneal thickness (CCT) was measured with the Spectral-Domain Optical Coherence Tomography (SD-OCT).
  
  
  RESULTS
  The study group's mean CH, CCT, IOPg, and IOPGAT values were lower than the control group (p < 0.05 for all variables). The mean CH, CRF, CCT, IOPg, and IOPGAT values were higher in active patients when compared to the inactive ones (p < 0.001, p < 0.001, p = 0.013, p = 0.021, and p = 0.002, respectively).
  
  
  CONCLUSIONS
  AS patients have lower CCT, CH, IOPg, and IOPGAT when compared with healthy subjects. In the active stage of AS, patients present with higher levels of corneal biomechanical parameters with thicker corneas. IOPcc is a more accurate measurement than IOPGAT or IOPg in AS patients.
authors.affiliation: Ophthalmology Department, Ataturk Research and Training Hospital, Ankara, Turkey. drmehtap85@hotmail.com.
authors.forename: Mehtap
authors.initials: M
authors.lastname: Caglayan
authors.affiliation: Ophthalmology Department, Ataturk Research and Training Hospital, Ankara, Turkey.
authors.forename: Ozge
authors.initials: O
authors.lastname: Sarac
authors.affiliation: Ulucanlar Eye Research and Training Hospital, Ankara, Turkey.
authors.forename: Pinar
authors.initials: P
authors.lastname: Kosekahya
authors.affiliation: Rheumatology Department, Atatürk Research and Training Hospital, Yildirim Beyazit University, Ankara, Turkey.
authors.forename: Sukran
authors.initials: S
authors.lastname: Erten
authors.affiliation: Ophthalmology Department, Ataturk Research and Training Hospital, Ankara, Turkey.
authors.forename: Berna
authors.initials: B
authors.lastname: Ayan
authors.affiliation: Ophthalmology Department, Atatürk Research and Training Hospital, Yildirim Beyazit University, Ankara, Turkey.
authors.forename: Nurullah
authors.initials: N
authors.lastname: Cagil
mesh_terms: D000328:Adult; D003315:Cornea / Q000473:pathology / Q000503:physiopathology*; D003316:Corneal Diseases / Q000175:diagnosis / Q000209:etiology / Q000503:physiopathology*; D004548:Elasticity; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007429:Intraocular Pressure / Q000502:physiology*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D015203:Reproducibility of Results; D013167:Spondylitis, Ankylosing / Q000150:complications*; D041623:Tomography, Optical Coherence / Q000379:methods*; D055815:Young Adult
keywords: Ankylosing spondylitis; Central corneal thickness; Corneal hysteresis; Corneal resistance factor