Skip to main content Accessibility help

We use cookies to distinguish you from other users and to provide you with a better experience on our websites. Close this message to accept cookies or find out how to manage your cookie settings.

Close cookie message
×
Hostname: page-component-cd9895bd7-lnqnp Total loading time: 0 Render date: 2024-12-26T03:07:25.790Z Has data issue: false hasContentIssue false

6 - Ocular biomechanics

Published online by Cambridge University Press:  05 June 2012

C. Ross Ethier  and
Craig A. Simmons
C. Ross Ethier
Affiliation:
University of Toronto
Craig A. Simmons
Affiliation:
University of Toronto
Get access

Summary

At first, it may seem like biomechanics play little or no role in the eye, but nothing could be further from the truth. In fact, the eye is a pressurized, thick-walled shell with dedicated fluid production and drainage tissues, whose shape is controlled by biomechanical factors. It has internal and external musculature, a remarkably complex internal vascular system, and a variety of specialized fluid and solute transport systems. Biomechanics play a central role in accommodation (focussing near and far), as well as in common disorders such as glaucoma, macular degeneration, myopia (near-sightedness), and presbyopia (inability to focus on nearby objects). To appreciate the role of biomechanics in these processes we must first briefly review ocular anatomy.

Ocular anatomy

The eye is a remarkable organ. It functions like a camera, with an adjustable compound lens, an adjustable aperture (the pupil), and a light-sensitive medium (the retina) that converts photons into electrochemical signals (Fig. 6.1, color plate). The eye automatically adjusts pupil size and lens shape so that images are clear under a wide variety of lighting conditions and over a wide range of distances from the observer.

The outer coat of the eye is formed by the cornea and sclera, two tough connective tissues that together make up the corneoscleral shell. This shell is pierced at the back of the eye by the scleral canal and at other discrete locations by small vessels and nerves.

Type
Chapter
Information
Introductory Biomechanics
From Cells to Organisms
 , pp. 250 - 281
Publisher: Cambridge University Press
Print publication year: 2007

Access options

Get access to the full version of this content by using one of the access options below. (Log in options will check for institutional or personal access. Content may require purchase if you do not have access.)

References

Krey, H. F. and Bräuer, H.. Chibret Augenatlas: Eine Repetition für Ärtze mit Zeigetafeln Für Patienten (Munich: Chibret Medical Service, 1998).Google Scholar
Karim, S., Clark, R. A., Poukens, V. and Demer, J. L.. Demonstration of systematic variation in human intraorbital optic nerve size by quantitative magnetic resonance imaging and histology. Investigative Ophthalmology and Visual Science, 45 (2004), 1047–1051.CrossRefGoogle ScholarPubMed
Demer, J. L.. The orbital pulley system: a revolution in concepts of orbital anatomy. Annals of the New York Academy of Sciences, 956 (2002), 17–32.CrossRefGoogle ScholarPubMed
Bartels., S. P. Aqueous humor formation: fluid production by a sodium pump. In The Glaucomas, ed. Ritch, R., Shields, M. B. and Krupin, T.. (St. Louis, MO: Mosby, 1989), pp. 199–218.Google Scholar
Schottenstein, E. M.. Intraocular pressure. In The Glaucomas, ed. Ritch, R., Shields, M. B. and Krupin, T.. (St. Louis, MO: Mosby, 1989), pp. 301–317.Google Scholar
Quigley, H. A.. Number of people with glaucoma worldwide. British Journal of Ophthalmology, 80 (1996), 389–393.CrossRefGoogle ScholarPubMed
Quigley, H. A.. Neuronal death in glaucoma. Progress in Retinal and Eye Research, 18 (1999), 39–57.CrossRefGoogle ScholarPubMed
Gloster., J.Tonometry and Tonography (London: J. & A. Churchill, 1966).Google Scholar
Doughty, M. J. and Zaman, M. L.. Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach. Survey of Ophthalmology, 44 (2000), 367–408.CrossRefGoogle ScholarPubMed
Shih, C. Y., Graff, J. S. Zivin, Trokel, S. L. and Tsai, J. C.. Clinical significance of central corneal thickness in the management of glaucoma. Archives of Ophthalmology, 122 (2004), 1270–1275.CrossRefGoogle ScholarPubMed
Brandt, J. D.. Corneal thickness in glaucoma screening, diagnosis, and management. Current Opinion in Ophthalmology, 15 (2004), 85–89.CrossRefGoogle Scholar
Brubaker., R. F. Measurement of aqueous flow by fluorophotometry. In The Glaucomas, ed. Ritch, R., Shields, M. B. and Krupin, T.. (St. Louis, MO: Mosby, 1989), pp. 337–344.Google Scholar
Beck, A. D.. Review of recent publications of the Advanced Glaucoma Intervention Study. Current Opinion in Ophthalmology, 14 (2003), 83–85.CrossRefGoogle ScholarPubMed
Becker, B. and Neufeld, A. H.. Pressure dependence of uveoscleral outflow. Journal of Glaucoma, 11 (2002), 545.CrossRefGoogle ScholarPubMed
Linden, C. and Alm, A.. Prostaglandin analogues in the treatment of glaucoma. Drugs and Aging, 14 (1999), 387–398.CrossRefGoogle ScholarPubMed
Hogan, M. J., Alvarado, J. A. and Weddel, J. E.. Histology of the Human Eye (Philadelphia, PA: W. B. Saunders, 1971).Google Scholar
Ethier, C. R., Read, A. T. and Chan, D.. Biomechanics of Schlemm's canal endothelial cells: influence on F-actin architecture. Biophysical Journal, 87 (2004), 2828–2837.CrossRefGoogle ScholarPubMed
Mäepea, O. and Bill, A.. The pressures in the episcleral veins, schlemm's canal and the trabecular meshwork in monkeys: effects of changes in intraocular pressure. Experimental Eye Research, 49 (1989), 645–663.CrossRefGoogle ScholarPubMed
Mäepea, O. and Bill, A.. Pressures in the juxtacanalicular tissue and schlemm's canal in monkeys. Experimental Eye Research, 54 (1992), 879–883.CrossRefGoogle ScholarPubMed
Ethier, C. R.. The inner wall of schlemm's canal. Experimental Eye Research, 74 (2002), 161–172.CrossRefGoogle ScholarPubMed
Brubaker, R. F.. Determination of episcleral venous pressure in the eye. A comparison of three methods. Archives of Ophthalmology, 77 (1967), 110–114.CrossRefGoogle Scholar
Phelps, C. D. and Armaly, M. F.. Measurement of episcleral venous pressure. American Journal of Ophthalmology, 85 (1978), 35–42.CrossRefGoogle ScholarPubMed
Johnson, M. and Kamm, R. D.. The role of schlemm's canal in aqueous outflow from the human eye. Investigative Ophthalmology and Visual Science, 24 (1983), 320–325.Google ScholarPubMed
White, F. M.. Viscous Fluid Flow, 2nd edn (New York: McGraw-Hill, 1991).Google Scholar
Brubaker, R. F.. The effect of intraocular pressure on conventional outflow resistance in the enucleated human eye. Investigative Ophthalmology, 14 (1975), 286–292.Google ScholarPubMed
Shah, R. K. and London, A. L.. Laminar Flow Forced Convection in Ducts: A Source Book for Compact Heat Exchanger Analytical Data (New York: Academic Press, 1978).Google Scholar
Allingham, R. R., Kater, A. W. and Ethier, C. R.. Schlemm's canal and primary open angle glaucoma: correlation between schlemm's canal dimensions and outflow facility. Experimental Eye Research, 62 (1996), 101–109.CrossRefGoogle ScholarPubMed
Ethier, C. R., Kamm, R. D., Palaszewski, B. A., Johnson, M. C. and Richardson, T. M.. Calculation of flow resistance in the juxtacanalicular meshwork. Investigative Ophthalmology and Visual Science, 27 (1986), 1741–1750.Google Scholar
Alexander, J. P., Samples, J. R. and Acott, T. S.. Growth factor and cytokine modulation of trabecular meshwork matrix metalloproteinase and TIMP expression. Current Eye Research, 17 (1998), 276–285.CrossRefGoogle ScholarPubMed
Bradley, J. M., Kelley, M. J., Zhu, X., Anderssohn, A. M., Alexander, J. P.et al. Effects of mechanical stretching on trabecular matrix metalloproteinases. Investigative Ophthalmology and Visual Science, 42 (2001), 1505–1513.Google ScholarPubMed
Bradley, J. M., Vranka, J., Colvis, C. M., Conger, D. M., Alexander, J. P.et al. Effect of matrix metalloproteinases activity on outflow in perfused human organ culture. Investigative Ophthalmology and Visual Science, 39 (1998), 2649–2658.Google ScholarPubMed
Levick, J. R.. Flow through interstitium and other fibrous matrices. Quarterly Journal of Experimental Physiology, 72 (1987), 409–437.CrossRefGoogle ScholarPubMed
Johnson, M. and Erickson., K. Mechanisms and routes of aqueous humor drainage. In 4: Principles and Practices of Ophthalmology, ed. Albert, D. M. and Jakobiec, F. A.. (Philadelphia, PA: W. B. Saunders, 2000), pp. 2577–2595.Google Scholar
Ye, W., Gong, H., Sit, A., Johnson, M. and Freddo, T. F.. Interendothelial junctions in normal human schlemm's canal respond to changes in pressure. Investigative Ophthalmology and Visual Science, 38 (1997), 2460–2468.Google ScholarPubMed
Johnson, M., Shapiro, A., Ethier, C. R. and Kamm, R. D.. The modulation of outflow resistance by the pores of the inner wall endothelium. Investigative Ophthalmology and Visual Science, 33 (1992), 1670–1675.Google ScholarPubMed
Canning, C. R., Greaney, M. J., Dewynne, J. N. and Fitt, A. D.. Fluid flow in the anterior chamber of a human eye. IMA Journal of Mathematics Applied in Medicine and Biology, 19 (2002), 31–60.CrossRefGoogle ScholarPubMed
Heys, J. J. and Barocas, V. H.. A Boussinesq model of natural convection in the human eye and the formation of krukenberg's spindle. Annals of Biomedical Engineering, 30 (2002), 392–401.CrossRefGoogle ScholarPubMed
Heys, J. and Barocas, V. H.. Mechanical characterization of the bovine iris. Journal of Biomechanics, 32 (1999), 999–1003.CrossRefGoogle ScholarPubMed
Heys, J. J. and Barocas, V. H.. Computational evaluation of the role of accommodation in pigmentary glaucoma. Investigative Ophthalmology and Visual Science, 43 (2002), 700–708.Google ScholarPubMed
Heys, J. J., Barocas, V. H. and Taravella, M. J.. Modeling passive mechanical interaction between aqueous humor and iris. Journal of Biomechanical Engineering, 123 (2001), 540–547.CrossRefGoogle ScholarPubMed
Minckler, D. S.. Histology of optic nerve damage in ocular hypertension and early glaucoma. Survey of Ophthalmology, 33(Suppl) (1989), 401–402.CrossRefGoogle ScholarPubMed
Lodish, H., Berk, A., Zipursky, S. L., Matsudaira, P., Baltimore, D.et al. Molecular Cell Biology, 4th edn (New York: Freeman, 2000).Google Scholar
Anderson, D. R. and Hendrickson, A.. Effect of intraocular pressure on rapid axoplasmic transport in monkey optic nerve. Investigative Ophthalmology, 13 (1974), 771–783.Google ScholarPubMed
Minckler, D. S., Bunt, A. H. and Klock, I. B.. Radioautographic and cytochemical ultrastructural studies of axoplasmic transport in the monkey optic nerve head. Investigative Ophthalmology, 717 (1978), 33–50.Google Scholar
Quigley, H. A. and Anderson, D. R.. The dynamics and location of axonal transport blockade by acute intraocular pressure elevation in primate optic nerve. Investigative Ophthalmology, 15 (1976), 606–616.Google ScholarPubMed
Quigley, H. A., Flower, R. W., Addicks, E. M. and McLeod, D. S.. The mechanism of optic nerve damage in experimental acute intraocular pressure elevation. Investigative Ophthalmology and Visual Science, 19 (1980), 505–517.Google ScholarPubMed
Kerrigan-Baumrind, L. A., Quigley, H. A., Pease, M. E., Kerrigan, D. F. and Mitchell, R. S.. Number of ganglion cells in glaucoma eyes compared with threshold visual field tests in the same persons. Investigative Ophthalmology and Visual Science, 41 (2000), 741–748.Google ScholarPubMed
Quigley, H. A., Addicks, E. M., Green, W. R. and Maumenee, A. E.. Optic nerve damage in human glaucoma. II. The site of injury and susceptibility to damage. Archives of Ophthalmology, 99 (1981), 635–649.CrossRefGoogle Scholar
Quigley, H. A. and Addicks, E. M.. Regional differences in the structure of the lamina cribrosa and their relation to glaucomatous optic nerve damage. Archives of Ophthalmology, 99 (1981), 137–143.CrossRefGoogle ScholarPubMed
Hernandez, M. R.. The optic nerve head in glaucoma: role of astrocytes in tissue remodeling. Progress in Retinal and Eye Research, 19 (2000), 297–321.CrossRefGoogle ScholarPubMed
Anderson., D. R. Optic nerve blood flow. In Optic Nerve in Glaucoma, ed. Drance, S. M. and Anderson, D. R.. (New York: Kluger, 1995), pp. 311–331.Google Scholar
Cioffi., G. A. Vascular anatomy of the anterior optic nerve. In Current Concepts on Ocular Blood Flow in Glaucoma, ed. Pillunat, L. E., Harris, A., Anderson, D. A. and E. L. Greve, . (The Hague, Netherlands: Kugler, 1999), pp. 45–48.Google Scholar
Hayreh., S. S. Blood supply of the optic nerve head. A ‘reality check.’ In Current Concepts on Ocular Blood Flow in Glaucoma, ed. Pillunat, L. E., Harris, A., Anderson, D. A. and Greve, E. L.. (The Hague, Netherlands: Kugler, 1999), pp. 3–31.Google Scholar
Buskirk, E. M. and Cioffi., G. A. Microvasculature of the optic disc and glaucoma. In Glaucoma: Decision Making in Therapy, ed. Bucci, M. G.. (Milan: Springer Verlag, 1996).Google Scholar
Nesterov, A. P. and Egoriv., E. A. Pathological physiology of primary open angle glaucoma. In Glaucoma, ed. Cairns, J.. (Miami, FL: Grune and Stratton, 1986), pp. 382–396.Google ScholarPubMed
Yan, D. B., Metheetrairut, A., Coloma, F. M., Trope, G. E., Heathcote, J. G.et al. Deformation of the lamina cribrosa by elevated intraocular pressure. British Journal of Ophthalmology, 78 (1994), 643–648.CrossRefGoogle ScholarPubMed
Levy, N. S. and Crapps, E. E.. Displacement of optic nerve head in response to short-term intraocular pressure elevation in human eyes. Archives of Ophthalmology, 102 (1984), 782–786.CrossRefGoogle ScholarPubMed
Levy, N. S., Crapps, E. E. and Bonney, R. C.. Displacement of the optic nerve head. Response to acute intraocular pressure elevation in primate eyes. Archives of Ophthalmology, 99 (1981), 2166–2174.CrossRefGoogle ScholarPubMed
Yan, D. B., Flanagan, J. G., Farra, T., Trope, G. E. and Ethier, C. R.. Study of regional deformation of the optic nerve head using scanning laser tomography. Current Eye Research, 17 (1998), 903–916.CrossRefGoogle ScholarPubMed
He, D. Q. and Ren, Z. Q.. A biomathematical model for pressure-dependent lamina cribrosa behavior. Journal of Biomechanics, 32 (1999), 579–584.Google Scholar
Edwards, M. E. and Good, T. A.. Use of a mathematical model to estimate stress and strain during elevated pressure induced lamina cribrosa deformation. Current Eye Research, 23 (2001), 215–225.CrossRefGoogle ScholarPubMed
Timoshenko, S. and Woinowsky-Krieger, S.. Theory of Plates and Shells (New York: McGraw-Hill, 1959).Google Scholar
Jonas, J. B., Mardin, C. Y., Schlotzer-Schrehardt, U. and Naumann, G. O.. Morphometry of the human lamina cribrosa surface. Investigative Ophthalmology and Visual Science, 32 (1991), 401–405.Google ScholarPubMed
Timoshenko, S. and Goodier, J. N.. Theory of Elasticity (New York: McGraw-Hill, 1970).Google Scholar
Sigal, I. A., Flanagan, J. G., Tertinegg, I. and Ethier, C. R.. Finite element modeling of optic nerve head biomechanics. Investigative Ophthalmology and Visual Science, 45 (2004), 4378–4387.CrossRefGoogle ScholarPubMed
Edwards, M. E., Wang, S. S. and Good, T. A.. Role of viscoelastic properties of differentiated SH-SY5Y human neuroblastoma cells in cyclic shear stress injury. Biotechnology Progress, 17 (2001), 760–767.CrossRefGoogle ScholarPubMed
Margulies, S. S. and Thibault, L. E.. A proposed tolerance criterion for diffuse axonal injury in man. Journal of Biomechanics, 25 (1992), 917–923.CrossRefGoogle ScholarPubMed
Morrison, B. III, Cater, H. L., Wang, C. B., Thomas, F. C., Hung, C. T.et al. A tissue level tolerance criteria for living brain developed with an in vitro model of traumatic mechanical loading. Stapp Car Crash Journal, 47 (2003), 93–105.Google Scholar
Triyoso, D. H. and Good, T. A.. Pulsatile shear stress leads to DNA fragmentation in human SH-SY5Y neuroblastoma cell line. Journal of Physiology, 515(Pt 2) (1999), 355–365.CrossRefGoogle ScholarPubMed
Bellezza, A. J., Hart, R. T. and Burgoyne, C. F.. The optic nerve head as a biomechanical structure: initial finite element modeling. Investigative Ophthalmology and Visual Science, 41 (2000), 2991–3000.Google ScholarPubMed
Gray, H.. Anatomy of the Human Body, 20th edn: thoroughly reviewed and reedited by W. H. Lewis (Philadelphia, PA: Lea and Febiger, 1918).
Kolb, H., Fernandez, E. and Nelson, R.. Webvision: The Organization of the Retina and Visual System. Available at http://webvision.med.utah.edu/sretina.html (2005).PubMed
Collins, R. and Werff, T. J.. Mathematical Models of the Dynamics of the Human Eye, No. 34 of Lecture Notes in Biomathematics (Berlin: Springer Verlag, 1980).Google Scholar
Bill, A.. Blood circulation and fluid dynamics in the eye. Physiological Reviews, 55 (1975), 383–416.CrossRefGoogle Scholar
Wangsa-Wirawan, N. D. and Linsenmeier, R. A.. Retinal oxygen: fundamental and clinical aspects. Archives of Ophthalmology, 121 (2003), 547–557.CrossRefGoogle ScholarPubMed
Kamm., R. D. Flow through collapsible tubes. In Handbook of Bioengineering, ed. Skalak, R. and Chien, S.. (New York: McGraw-Hill, 1987), pp. 23.1–23.19.Google Scholar
Shapiro, A. H.. Steady flow in collapsible tubes. Journal of Biomechanical Engineering, 99 (1977), 126–147.CrossRefGoogle Scholar
Cole, D. F.. Aqueous humour formation. Documenta Ophthalmologica, 21 (1966), 116–238.CrossRefGoogle Scholar
Mäepea, O.. Pressures in the anterior ciliary arteries, choroidal veins and choriocapillaris. Experimental Eye Research, 54 (1992), 731–736.CrossRefGoogle ScholarPubMed
Grunwald, J. E., Petrig, B. L. and Robinson, F.. Retinal blood flow autoregulation in response to an acute increase in blood pressure. Investigative Ophthalmology and Visual Science, 27 (1986), 1706–1712.Google Scholar
Stalford, C. B.. Update for nurse anesthetists. The Starling resistor: a model for explaining and treating obstructive sleep apnea. AANA Journal, 72 (2004), 133–138.Google ScholarPubMed
Huang, L., Quinn, S. J., Ellis, P. D. M. and Ffowcs, J. E. Williams. Biomechanics of snoring. Endeavour, 19 (1995), 96–100.CrossRefGoogle ScholarPubMed
Gavriely, N., Kelly, K. B., Grotberg, J. B. and Loring, S. H.. Forced expiratory wheezes are a manifestation of airway flow limitation. Journal of Applied Physiology, 62 (1987), 2398–2403.CrossRefGoogle ScholarPubMed
Brook, B. S. and Pedley, T. J.. A model for time-dependent flow in (giraffe jugular) veins: uniform tube properties. Journal of Biomechanics, 35 (2002), 95–107.CrossRefGoogle ScholarPubMed
Bathe, M. and Kamm, R. D.. A fluid–structure interaction finite element analysis of pulsatile blood flow through a compliant stenotic artery. Journal of Biomechanical Engineering, 121 (1999), 361–369.CrossRefGoogle ScholarPubMed

Save book to Kindle

To save this book to your Kindle, first ensure [email protected] is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below. Find out more about saving to your Kindle.

Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.

Find out more about the Kindle Personal Document Service.

Available formats
×

Save book to Dropbox

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Dropbox.

Available formats
×

Save book to Google Drive

To save content items to your account, please confirm that you agree to abide by our usage policies. If this is the first time you use this feature, you will be asked to authorise Cambridge Core to connect with your account. Find out more about saving content to Google Drive.

Available formats
×