Intraocular Pressure (IOP) is defined as the pressure of aqueous in the eye. It has been reported that the normal range of IOP should be within the 10-20 mmHg with an average of 15.50 mmHg among the ophthalmologists. Keratoconus is an anti-inflammatory eye disorder that debilitated cornea unable to reserve the normal structure contrary to the IOP in the eye. Consequently, the cornea would bulge outward and invoke a conical shape following by distorted vision. In addition, it is known that any alterations in the structure and composition of the lens and cornea would exceed a change of the eye ball as well as the mechanical and optical properties of the eye.
OBJECTIVE:
Understanding the precise alteration of the eye components' stresses and deformations due to different IOPs could help elucidate etiology and pathogenesis to develop treatments not only for keratoconus but also for other diseases of the eye.
METHODS:
In this study, at three different IOPs, including 10, 20, and 30 mmHg the stresses and deformations of the human eye components were quantified using a Three-Dimensional (3D) computational Fluid-Structure Interaction (FSI) model of the human eye.
RESULTS:
The results revealed the highest amount of von Mises stress in the bulged region of the cornea with 245 kPa at the IOP of 30 mmHg. The lens was also showed the von Mises stress of 19.38 kPa at the IOPs of 30 mmHg. In addition, by increasing the IOP from 10 to 30 mmHg, the radius of curvature in the cornea and lens was increased accordingly. In contrast, the sclera indicated its highest stress at the IOP of 10 mmHg due to over pressure phenomenon. The variation of IOP illustrated a little influence in the amount of stress as well as the resultant displacement of the optic nerve.
CONCLUSION:
These results can be used for understanding the amount of stresses and deformations in the human eye components due to different IOPs as well as for clarifying significant role of IOP on the radius of curvature of the cornea and the lens.
SawaguchiS, FukuchiT, AbeH, KaiyaT, SugarJ, YueBY. Three-dimensional scanning electron microscopic study of keratoconus corneas. Arch Ophthalmol. 1998; 116(1): 62-8.
2.
SnellRS, LempMA. Clinical anatomy of the eye: Wiley-Blackwell; 1997.
3.
TaberneroJ, VazquezD, SeidemannA, UttenweilerD, SchaeffelF. Effects of myopic spectacle correction and radial refractive gradient spectacles on peripheral refraction. Vision Res. 2009; 49(17): 2176-86.
4.
GefenA, ShalomR, EladD, MandelY. Biomechanical analysis of the keratoconic cornea. J Mech Behav Biomed Mater. 2009; 2(3): 224-36.
5.
MeekKM, BooteC. The organization of collagen in the corneal stroma. Exp Eye Res. 2004; 78(3): 503-12.
6.
ShinTJ, VitoRP, JohnsonLW, McCareyBE. The distribution of strain in the human cornea. J Biomech. 1997; 30(5): 497-503.
7.
KomaiY, UshikiT. The three-dimensional organization of collagen fibrils in the human cornea and sclera. Invest Ophthalmol Vis Sci. 1991; 32(8): 2244-58.
8.
HukinsDW, AspdenRM. Composition and properties of connective tissues. Trends Biochem Sci. 1985; 10(7): 260-4.
9.
TuoriAJ, VirtanenI, AineE, KalluriR, MinerJ, UusitaloHM. The immunohistochemical composition of corneal basement membrane in keratoconus. Current Eye Res. 1997; 16(8): 792-801.
10.
ChengEL, MaruyamaI, SundarRajN, SugarJ, FederRS, YueBY. Expression of type XII collagen and hemidesmosome-associated proteins in keratoconus corneas. Current Eye Res. 2001; 22(5): 333-40.
EdmundC. Corneal topography and elasticity in normal and keratoconic eyes. A methodological study concerning the pathogenesis of keratoconus. Acta Ophthalmologica Supplement. 1988; 193: 1-36.
13.
VinciguerraP, AlbèE, TrazzaS, RosettaP, VinciguerraR, SeilerT, et al. Refractive, topographic, tomographic, and aberrometric analysis of keratoconic eyes undergoing corneal cross-linking. Ophthalmology. 2009; 116(3): 369-78.
14.
DuppsWJ, WilsonSE. Biomechanics and wound healing in the cornea. Exp Eye Res. 2006; 83(4): 709-20.
15.
BryantMR, McDonnellPJ. Constitutive laws for biomechanical modeling of refractive surgery. J Biomech Eng. 1996; 118(4): 473-81.
16.
AndersonK, El-SheikhA, NewsonT. Application of structural analysis to the mechanical behaviour of the cornea. J Royal Soc Interface. 2004; 1(1): 3-15.
17.
PandolfiA, ManganielloF. A model for the human cornea: constitutive formulation and numerical analysis. Biomech Model Mechanobiol. 2006; 5(4): 237-46.
18.
AndreassenTT, SimonsenAH, OxlundH. Biomechanical properties of keratoconus and normal corneas. Exp Eye Res. 1980; 31(4): 435-41.
19.
BrooksA, RobertsonIF, MahoneyA. Ocular rigidity and intraocular pressure in keratoconus. Austr J Opthalmol. 1984; 12(4): 317-24.
20.
HartsteinJ, BeckerB. Research into the pathogenesis of keratoconus: a new syndrome: low ocular rigidity, contact lenses, and keratoconus. Arch Ophthalmol. 1970; 84(6): 728-9.
21.
OrssengoGJ, PyeDC. Determination of the true intraocular pressure and modulus of elasticity of the human cornea in vivo. Bulletin Math Biol. 1999; 61(3): 551-72.
22.
HerndonLW. Measuring intraocular pressure-adjustments for corneal thickness and new technologies. Current Opinion Ophthalmol. 2006; 17(2): 115-9.
23.
WangR, OkumaE. Biomechanical response of the cornea to phototherapeutic keratectomy when treated as a fluid-filled porous material. J Refract Surg. 2002; 18(5): S593.
24.
MamelokAE, PosnerA. Measurements of Corneal Elasticity: In relation to disease, using the Wiegersma elastometer. Am J Ophthalmol. 1955; 39(6): 817-21.
25.
LiuJ, RobertsCJ. Influence of corneal biomechanical properties on intraocular pressure measurement: quantitative analysis. J Cataract Refract Surg. 2005; 31(1): 146-55.
26.
PallikarisIG, KymionisGD, GinisHS, KounisGA, TsilimbarisMK. Ocular rigidity in living human eyes. Invest Ophthalmol Vis Sci. 2005; 46(2): 409-14.
27.
OrtizD, PiñeroD, ShabayekMH, Arnalich-MontielF, AlióJL. Corneal biomechanical properties in normal, post-laser in situ keratomileusis, and keratoconic eyes. J Cataract Refract Surg. 2007; 33(8): 1371-5.
28.
KarimiA, RazaghiR, NavidbakhshM, SeraT, KudoS. Dynamic finite element simulation of the gunshot injury to the human forehead protected by polyvinyl alcohol sponge. J Mater Sci Mater Med. 2016; 27(4): 74-85.
29.
KarimiA, RazaghiR, NavidbakhshM, SeraT, KudoS. Computing the stresses and deformations of the human eye components due to a high explosive detonation using fluid-structure interaction model. Injury. 2016; 47: 1042-50.
30.
KarimiA, RazaghiR, NavidbakhshM, SeraT, KudoS. Quantifying the injury of the human eye components due to tennis ball impact using a computational fluid-structure interaction model. Sports Eng. 2016; 19: 105-15.
31.
DjotyanGP, SoongHK, MianS, FernándezDC, KurtzRM, JuhaszT. Finite-element modeling of posterior lamellar keratoplasty: Construction of theoretical nomograms for induced refractive errors. Ophthalmic Res. 2006; 38(6): 329-34.
32.
PierscionekBK, Asejczyk-WidlickaM, SchacharRA. The effect of changing intraocular pressure on the corneal and scleral curvatures in the fresh porcine eye. Br J Ophthalmol. 2007; 91(6): 801-3.
33.
Asejczyk-WidlickaM, śródkaD, KasprzakH, PierscionekB. Modelling the elastic properties of the anterior eye and their contribution to maintenance of image quality: the role of the limbus. Eye. 2007; 21(8): 1087-94.
34.
HjortdalJØ. Regional elastic performance of the human cornea. J Biomech. 1996; 29(7): 931-42.
35.
BronAJ. Keratoconus. Cornea. 1987; 7(3): 163-9.
36.
EmaraB, ProbstLE, TingeyDP, KennedyDW, WillmsLJ, MachatJ. Correlation of intraocular pressure and central corneal thickness in normal myopic eyes and after laser in situ keratomileusis. J Cataract Refract Surg. 1998; 24(10): 1320-5.
37.
ManualL-DKUs, VolumeI. Version 971. Livermore Software Technology Corporation. 2007; 7374.
38.
KarimiA, NavidbakhshM, RazaghiR. A finite element study of balloon expandable stent for plaque and arterial wall vulnerability assessment. J Appl Phys. 2014; 116(4): 044701-10.
39.
KarimiA, NavidbakhshM, RazaghiR. Plaque and arterial vulnerability investigation in a three-layer atherosclerotic human coronary artery using computational fluid-structure interaction method. J Appl Phys. 2014; 116(6): 064701-10.
40.
KarimiA, NavidbakhshM, YamadaH, RazaghiR. A nonlinear finite element simulation of balloon expandable stent for assessment of plaque vulnerability inside a stenotic artery. Med Biol Eng Comput. 2014; 52(7): 589-99.
41.
KarimiA, NavidbakhshM, RazaghiR. Dynamic simulation and finite element analysis of the human mandible injury protected by polyvinyl alcohol sponge. Mater Sci Eng C. 2014; 42: 608-14.
42.
KrachmerJH, FederRS, BelinMW. Keratoconus and related noninflammatory corneal thinning disorders. Surv Ophthalmol. 1984; 28(4): 293-322.
43.
SakamotoY, SasakiK. Accuracy of Biometrical Data Obtained from the NIDEKEAS-1000. Ophthalmic Res. 1994; 26(Suppl. 1): 26-32.
44.
BurnsDM, JohnstonFM, FrazerDG, PattersonC, JacksonAJ. Keratoconus: an analysis of corneal asymmetry. Br J Ophthalmol. 2004; 88(10): 1252-5.
ZuckermanA. Occular injuries resulted from the war. Trans Opthal Soc UK. 1941; 61: 45-50.
47.
StitzelJD, DumaSM, CormierJM, HerringIP, editors. A nonlinear finite element model of the eye with experimental validation for the prediction of globe rupture. Sae conference proceedings p; 2002: SAE; 1999.
48.
HeysJJ, BarocasVH, TaravellaMJ. Modeling passive mechanical interaction between aqueous humor and iris. J Biomech Eng. 2001; 123(6): 540-7.
49.
ZhangK, QianX, MeiX, LiuZ. An inverse method to determine the mechanical properties of the iris in vivo. Biomed Eng Online. 2014; 13(1): 66.
50.
LiuX, WangL, WangC, FanJ, LiuS, FanY. Prediction of globe rupture caused by primary blast: A finite element analysis. Comput Methods Biomech Biomed Engin. 2015; 18(9): 1024-9.
51.
SchoemakerI, HoefnagelPP, MastenbroekTJ, KolffCF, SchutteS, van der HelmFC, et al. Elasticity, viscosity, and deformation of orbital fat. Invest Ophthalmol Vis Sci. 2006; 47(11): 4819-26.
52.
LeeB, LittM, BuchsbaumG. Rheology of the vitreous body. Part I: Viscoelasticity of human vitreous. Biorheology. 1991; 29(5-6): 521-33.
