Corneal stiffness affects IOP elevation during rapid volume change in the eye
Jun Liu 1*
and
Xiaoyin He 2
1 Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States; Ophthalmology, The Ohio State University, Columbus, Ohio, United States
2 Biomedical Engineering, The Ohio State University, Columbus, Ohio, United States
* To whom correspondence should be addressed. E-mail: liu.314{at}osu.edu.
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Abstract |
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Purpose: To investigate whether corneal stiffness affects the elevation of intraocular pressure after an acute increase in the volume of ocular fluid.
Methods: Saline (a total of 200 µl) was infused into porcine globes before and after corneal stiffening. The intraocular pressure was continuously monitored by a pressure sensor that was cannulated to the vitreous chamber. Corneal stiffening was achieved by immersing the corneas in a 1% or 4% glutaraldehyde solution for 20 min. Corneal strips were dissected from the globes, and the stress-strain relationships were measured using a Rheometrics System Analyzer. The mean secant modulus of each group of corneas at 5% strain was calculated. Control eyes with no corneal stiffening were also tested.
Results: A significantly higher IOP elevation was observed in the globes after the corneas were stiffened (Mean ± SD, 14.9 ± 1.9 mmHg before stiffening vs. 19.1 ± 2.6 mmHg after 1% glutaraldehyde treatment and 24.3 ± 1.9 mmHg after 4% glutaraldehyde treatment at 200 µl infusion, P<0.001). The control group showed no change in IOP elevation. The 5% secant modulus was 0.46 ± 0.24 MPa, 1.63 ± 0.41 MPa, and 2.78 ± 1.04 MPa (Mean ± SD), respectively, for the original corneal tissue and those with 1% or 4% glutaraldehyde treatment.
Conclusions: This study showed that stiffened corneas induced substantially higher IOP elevations when all other geometrical and material properties of the eye remained essentially the same. The results suggested that corneal stiffness may play an important role in determining IOP elevation caused by an acute increase in the volume of intraocular fluid.
Key Words:
corneal biomechanics, glaucoma, intraocular pressure, IOP fluctuation, corneal stiffness
