Abstract
Purpose
To facilitate the protection of corneal stability during corneal epithelium defects by determining the effect of solution pH on corneal stroma biomechanics.
Methods
Thirty rabbit corneas were extracted, and the epithelium was scraped off. The samples were immediately subjected to inflation tests with pressures ranging from 0.3 to 6 kPa at baseline and in three subsequent test cycles. During a 10-min interval between cycles, specimens were randomly divided into four groups; in three of these groups, phosphate-buffered saline (PBS) drops with pH values of 6.9, 7.4, or 7.9 were applied to the surface once per minute, whereas the fourth group did not receive drops.
Results
The corneal thickness significantly increased following the administration of PBS, while the corneal tangent modulus significantly decreased. At 2.5 and 4.5 kPa, the modulus reduction was significantly smaller in the specimens treated with pH 6.9 PBS than in those treated with pH 7.4 or 7.9 PBS, adjusted for changes in corneal thickness. Linear fitting of the pressure-modulus plot revealed that the regression coefficient significantly decreased over time. The reduction in the coefficient was most prominent in the PBS-treated groups, and the administration of pH 6.9 PBS elicited the smallest reduction among those three groups, adjusted for corneal thickness changes.
Conclusion
The study demonstrated that the administration of PBS drops with various pH values affected corneal biomechanics independent of corneal stromal swelling, and the impact of slightly acidic PBS was minimal. The effect became more prominent as posterior pressure increased. The research provides the basis for mediating the pH value of tear film and drops to maintain biomechanical stability of epithelium defects corneal stroma.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
Data availability
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.
References
Sridhar MS (2018) Anatomy of cornea and ocular surface. Indian J Ophthalmol 66(2):190–194. https://doi.org/10.4103/ijo.IJO_646_17
Kling S, Hafezi F (2017) Corneal biomechanics - a review. Ophthalmic Physiol Opt 37(3):240–252. https://doi.org/10.1111/opo.12345
Ni S, Yu J, Bao F, Li J, Elsheikh A, Wang Q (2011) Effect of glucose on the stress-strain behavior of ex-vivo rabbit cornea. Exp Eye Res 92(5):353–360. https://doi.org/10.1016/j.exer.2011.02.005
Spoerl E, Zubaty V, Raiskup-Wolf F, Pillunat LE (2007) Oestrogen-induced changes in biomechanics in the cornea as a possible reason for keratectasia. Br J Ophthalmol 91(11):1547–1550. https://doi.org/10.1136/bjo.2007.124388
Ma J, Wang Y, Wei P, Jhanji V (2018) Biomechanics and structure of the cornea: implications and association with corneal disorders. Surv Ophthalmol 63(6):851–861. https://doi.org/10.1016/j.survophthal.2018.05.004
DelMonte DW, Kim T (2011) Anatomy and physiology of the cornea. J Cataract Refract Surg 37(3):588–598. https://doi.org/10.1016/j.jcrs.2010.12.037
Boote C, Dennis S, Huang Y, Quantock AJ, Meek KM (2005) Lamellar orientation in human cornea in relation to mechanical properties. J Struct Biol 149(1):1–6. https://doi.org/10.1016/j.jsb.2004.08.009
Harvitt DM, Bonanno JA (1998) pH dependence of corneal oxygen consumption. Invest Ophthalmol Vis Sci 39(13):2778–2781
Gioia M, Fasciglione GF, Monaco S, Iundusi R, Sbardella D, Marini S, Tarantino U, Coletta M (2010) pH dependence of the enzymatic processing of collagen I by MMP-1 (fibroblast collagenase), MMP-2 (gelatinase A), and MMP-14 ectodomain. J Biol Inorg Chem 15(8):1219–1232. https://doi.org/10.1007/s00775-010-0680-8
Tsubota K, Mashima Y, Murata H, Yamada M, Sato N (1995) Corneal epithelium following penetrating keratoplasty. Br J Ophthalmol 79(3):257–260. https://doi.org/10.1136/bjo.79.3.257
Prabhasawat P, Kosrirukvongs P, Booranapong W, Vajaradul Y (2000) Application of Preserved Human Amniotic Membrane for Corneal Surface Reconstruction. Cell Tissue Banking 1(3):213–222. https://doi.org/10.1023/a:1026542702099
Huang Y, Meek KM (1999) Swelling studies on the cornea and sclera: the effects of pH and ionic strength. Biophys J 77(3):1655–1665. https://doi.org/10.1016/S0006-3495(99)77013-X
Van Haeringen NJ (1981) Clinical biochemistry of tears. Surv Ophthalmol 26(2):84–96. https://doi.org/10.1016/0039-6257(81)90145-4
Elsheikh A, Wang D, Pye D (2007) Determination of the modulus of elasticity of the human cornea. J Refract Surg 23(8):808–818
Hatami-Marbini H, Etebu E (2013) Hydration dependent biomechanical properties of the corneal stroma. Exp Eye Res 116:47–54. https://doi.org/10.1016/j.exer.2013.07.016
Hatami-Marbini H, Rahimi A (2014) The relation between hydration and mechanical behavior of bovine cornea in tension. J Mech Behav Biomed Mater 36:90–97. https://doi.org/10.1016/j.jmbbm.2014.03.011
Fratzl P, Daxer A (1993) Structural transformation of collagen fibrils in corneal stroma during drying. An x-ray scattering study Biophys J 64(4):1210–1214. https://doi.org/10.1016/S0006-3495(93)81487-5
Chen S, Mienaltowski MJ, Birk DE (2015) Regulation of corneal stroma extracellular matrix assembly. Exp Eye Res 133:69–80. https://doi.org/10.1016/j.exer.2014.08.001
Hassell JR, Birk DE (2010) The molecular basis of corneal transparency. Exp Eye Res 91(3):326–335. https://doi.org/10.1016/j.exer.2010.06.021
Pierre J (1979) The evolution of the thickness of rabbit corneas in hydratation, the influence of pH and composition of the solution (author's transl) (Evolution de l'épaisseur des cornées de lapins en cours d'hydratation. Influence du pH et de la composition du milieu hydratant). J Fr Ophtalmol 2(3): 199–204
Elliott GF, Goodfellow JM, Woolgar AE (1980) Swelling studies of bovine corneal stroma without bounding membranes. J Physiol 298:453–470. https://doi.org/10.1113/jphysiol.1980.sp013094
Doughty MJ (1999) Re-assessment of the potential impact of physiologically relevant pH changes on the hydration properties of the isolated mammalian corneal stroma. Biochim Biophys Acta 1472(1–2):99–106. https://doi.org/10.1016/s0304-4165(99)00109-9
Doughty MJ, Bergmanson JPG (2008) Use of a corneal stroma perfusion technique and transmission electron microscopy to assess ultrastructural changes associated with exposure to slightly acidic pH 5.75 solutions. Curr Eye Res 33(1):45–57. https://doi.org/10.1080/02713680701805742
Meek KM, Boote C (2004) The organization of collagen in the corneal stroma. Exp Eye Res 78(3):503–512. https://doi.org/10.1016/j.exer.2003.07.003
Blackburn BJ, Jenkins MW, Rollins AM, Dupps WJ (2019) A review of structural and biomechanical changes in the cornea in aging, disease, and photochemical crosslinking. Frontiers Bioengin biotechnol 7:66. https://doi.org/10.3389/fbioe.2019.00066
Elsheikh A, Alhasso D, Rama P (2008) Biomechanical properties of human and porcine corneas. Exp Eye Res 86(5):783–790. https://doi.org/10.1016/j.exer.2008.02.006
Funding
This work was supported by grants from the Chinese Capital’s Funds for Health Improvement and Research (grant number: CFH2018-2–4093) and the National Science and Technology Major Project (grant number: 2018ZX10101004). The sponsors or funding organizations had no role in the design or conduct of this research.
Author information
Authors and Affiliations
Contributions
YW contributed to the conceptualization and methodology of the research, performed the inflation test and data analysis, and wrote the original draft; JM prepared the specimens, analyzed the data, and reviewed the original draft; SW wrote the MATLAB program, analyzed the data, and reviewed the draft; YL performed the inflation test and reviewed the draft; XL contributed to the conceptualization, methodology and supervision and reviewed the draft. All of the authors contributed to the revision of the draft and are responsible for the final approval.
Corresponding author
Ethics declarations
Conflict of interests
The authors declare that they have no competing interests.
Ethical approval
The research protocol was approved by the ethics committee of Peking University Third Hospital; the approval number was 2017–0006.
Consent to participate
The research did not involve human subjects.
Additional information
Publisher's Note
Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
About this article
Cite this article
Wang, Y., Ma, J., Wei, S. et al. Investigation of the effect of solution pH value on rabbit corneal stroma biomechanics. Int Ophthalmol 42, 2255–2265 (2022). https://doi.org/10.1007/s10792-022-02226-4
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s10792-022-02226-4