The sclera plays a leading role in the biomechanical deformation of the cornea in air-puff induced deformation, which may have important clinical implications, a new study suggests.

Researchers from Ohio State University used a two-dimensional axisymmetric model of the whole human eye to examine the effects scleral stiffness and intraocular pressure (IOP) had on the maximum apical displacement of the cornea. The model was comprised of the cornea, sclera, vitreous and surrounding air region. The study replicated the velocity and pressure profiles of an air-puff from a dynamic Scheimpflug analyzer. Investigators simulated IOP as a uniform pressure on the globe interior and compared the simulation results with data from ex vivo scleral stiffening experiments with human donor globes. 

The study’s model predicted decreased maximum apical displacement with increased IOP and increased ratio of scleral-to-corneal Young’s moduli. These predictions were in good agreement—within one standard deviation—with results from ex vivo scleral stiffening experiments using human donor eyes, researchers noted.

“These findings demonstrate the importance of scleral material properties on the biomechanical deformation response of the cornea in air-puff induced deformation,” researchers said. 

The results of an air-puff test are often considered to be solely due to IOP and corneal properties, they added. “The current study showed that the stiffer the sclera, the greater will be the limitation on corneal deformation, separately from IOP. This may have important clinical implications to interpreting the response of the cornea under air-puff loading in pathologic conditions,” investigators said.

Nguyen BA, Roberts CJ, Reilly MA. Biomechanical impact of the sclera on corneal deformation response to an air-puff: a finite-element study. Front Bioeng Biotechnol. January 10, 2019. [Epub ahead of print].