Abstract
PURPOSE: To evaluate the influence of ocular shell biomechanical characteristics on corneal deformation response to an air puff.
SETTING: The Ohio State University, Columbus, Ohio, USA.
DESIGN: Experimental study.
METHODS: Twenty-four eyes of 12 human donors were obtained in matched pairs. One eye was secured in a purpose-designed whole globe mount (whole-globe group). The cornea from the fellow eye was placed in a Barron artificial anterior chamber (artificial-chamber group). The corneas were mounted sequentially and connected to a pressure-control system. Deformation data were acquired using the Corvis ST, a dynamic Scheimpflug analyzer. Internal pressure was set to 10, 20, 30, 40, and 50 mm Hg; at least 4 examinations were performed at each pressure.
RESULTS: Statistically significantly higher maximum deformation amplitude was observed in the whole-globe group than in the artificial-chamber group at all pressures. The mean amplitude differences were 1.006 mm +/- 0.238 [SD], 0.614 +/- 0.137 mm, 0.384 +/- 0.099 mm, 0.229 +/- 0.087 mm, and 0.133 +/- 0.068 mm at 10, 20, 30, 40, and 50 mm Hg, respectively (P<.0001, P<.0001, P<.0001, P<.0001, and P<.0002, respectively). Nonlinear regression of the deformation amplitude differences between pairs showed a significant decrease with increasing pressure (P<.0001, R-2 = 0.8385).
CONCLUSIONS: The deformation response to an air puff was affected by the type of mount used, with a stiffer shell producing a stiffer corneal response and decreasing differences at higher internal pressures. In vivo air-puff examinations may be affected by scleral stiffness in addition to the cornea. (C) 2014 ASCRS and ESCRS