The effect of changing intraocular pressure on the corneal and scleral curvatures in the fresh porcine eye
- Barbara K Pierscionek (b.pierscionek{at}ulster.ac.uk),
- Magdalena Widlicka (m.widlicka{at}ulster.ac.uk),
- Ronald A. Schachar (ron{at}2ras.com)
- University of Ulster, United Kingdom
- University of Ulster, United Kingdom
- University of Texas at Arlington, United States
- Published Online First 6 December 2006
Abstract
Aim: To measure cornea and scleral radii of curvature in response to intraocular pressure.
Methods: Using digital photographic profile images of sixteen fresh porcine eyes, the curvatures of the cornea and sclera were determined in response to five consecutive incremental 100 ml saline intravitral injections. Intraocular pressure (IOP) was measured and ocular rigidity calculated. Elastic moduli of the cornea and sclera were estimated.
Results: Intraocular pressure and the radius of curvature of the sclera increased linearly with increasing volume. There was no statistical change in corneal curvature. The elasticity of the cornea and sclera was constant over the 15 mm Hg to 50 mm Hg increase in IOP. The estimated range of the elastic moduli of the cornea and sclera were respectively 0.07 MPa to 0.29 MPa and 0.2 MPa to 0.5 MPa. The scleral rigidity ranges from 0.0017 to 0.0022.
Conclusions: The elastic moduli of the cornea and sclera are independent of IOP. The modulus of elasticity of the sclera is higher than that of the cornea. Elevation of IOP changes the curvature of the sclera but not the cornea. Porcine scleral rigidity is similar to human scleral rigidity. Scleral curvature may be a novel method for measuring IOP.
