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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.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.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).During corneal topography imaging, the Valsalva maneuver observed in patients with keratoconus does not typically cause any significant change in corneal morphology.