Effect of Solution pH on the Biomechanics of Intact Cornea From Inflation Tests

Abstract

Purpose

To investigate the effect of different pH phosphate buffer solution (PBS) drops on intact corneal biomechanics.

Methods

Intact rabbit cornea with a 3 mm scleral skirt was sampled and immediately applied in inflation tests within 5 min. After preconditioning, a stable loading cycle from 0.3 to 6 kPa was performed followed by a 10 min interval. During the interval, the samples were randomized into four groups, with one control group receiving no drops and three groups with PBS drops of pH 6.9, 7.4 or 7.9 administration on the surface once per minute. The pressure and displacement were collected at the baseline and 10, 20 and 30 min following the administration.

Results

Continuous corneal thickness increase was manifested following the administration of PBS but not in the control group. There was significant swelling-independent corneal modulus reduction after PBS administration, which occurred mainly in the first 10 min. PBS of pH 6.9 achieved significantly smaller modulus reduction than that with pH 7.4 PBS adjusted for thickness changes (p < 0.05). Pressure-modulus curve linear fitting demonstrated that the curve coefficient significantly reduced following PBS administration, and the coefficient decline was smallest with pH 6.9 PBS among three PBS administration groups (p < 0.05).

Conclusions

The study demonstrated that the PBS drops of various pH administration could decrease the corneal stiffness independent of corneal swelling. Following the PBS administration, the stiffness changes were more prominent as the posterior pressure increased, and the minimal effect was achieved with slightly acidic PBS. The research provides the essence for stabilizing the corneal biomechanical properties by regulating the pH value of tear film and intraocular pressure.

Keywords:

• pH value
• central cornea thickness
• corneal biomechanics
• epithelization
• inflation test

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

The raw data applied to conclude in the present manuscript will be made available by the authors without undue reservation to any qualified researchers following the publication.

Additional information

Funding

This work was supported by the grant from Chinese Capital’s Funds for Health Improvement and Research [Grant number: CFH2018-2-4093] and National Science and Technology Major Project [Grant number: 2018ZX10101004]. The sponsor or funding organization had no role in the design or conduct of this research.