title: Does Valsalva Maneuver Affect Corneal Morphology in Eyes With Keratoconus?
abstract: OBJECTIVE
  The aim of this study was to investigate the effect of the Valsalva maneuver on corneal morphology and anterior chamber parameters in patients with keratoconus.
  
  
  METHODS
  A total of 39 eyes from 39 patients with keratoconus and 41 eyes from 41 age-matched and gender-matched healthy individuals were included in this cross-sectional study. Measurements of corneal front keratometry values (K-flat, K-steep, and K-max), central corneal thickness, corneal apex thickness, thinnest corneal thickness, corneal volume, anterior chamber volume (ACV), anterior chamber depth (ACD), and iridocorneal angle (ICA) were performed with a Pentacam Scheimpflug camera (Oculus, Germany) before and during the Valsalva maneuver. Changes in the anterior segment parameters from baseline and during the Valsalva maneuver and the differences in parameters between the keratoconus group and the control group were analyzed. A P value less than 0.05 was accepted as statistically significant.
  
  
  RESULTS
  In the patients with keratoconus, the Valsalva maneuver did not have any significant influence on the corneal parameters (P>0.05). However, ACV, ACD, and ICA decreased markedly during the Valsalva maneuver (P=0.006, P=0.048, and P=0.025, respectively). Changes caused by the Valsalva maneuver were similar for all parameters when compared with those in healthy individuals (P>0.05).
  
  
  CONCLUSIONS
  During corneal topography imaging, the Valsalva maneuver observed in patients with keratoconus does not typically cause any significant change in corneal morphology.
authors.affiliation: Department of Ophthalmology (N.D., Z.D., A.C., A.S.K.H., H.B.A.), Kayseri Education and Research Hospital, Kayseri, Turkey; and Department of Ophthalmology (H.A.), Atatürk Education and Research Hospital, Ankara, Turkey.
authors.forename: Necati
authors.initials: N
authors.lastname: Duru
authors.forename: Zeynep
authors.initials: Z
authors.lastname: Duru
authors.forename: Ayşe
authors.initials: A
authors.lastname: Çiçek
authors.forename: Hasan
authors.initials: H
authors.lastname: Altınkaynak
authors.forename: Arzu Seyhan
authors.initials: AS
authors.lastname: Karatepe Haşhaş
authors.forename: Hasan Basri
authors.initials: HB
authors.lastname: Arifoğlu
mesh_terms: D000293:Adolescent; D000328:Adult; D003315:Cornea / Q000473:pathology*; D063171:Corneal Pachymetry; D019781:Corneal Topography; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007640:Keratoconus / Q000473:pathology*; D008297:Male; D011446:Prospective Studies; D014636:Valsalva Maneuver; D014792:Visual Acuity / Q000502:physiology; D055815:Young Adult