Skip to main content
SpringerLink
Log in

Assessment of Corneal Shape

  • Chapter
  • First Online:
Corneal Topography

  • 997 Accesses

Abstract

The shape of the anterior corneal surface can be measured in terms of height or elevation, slope and radius of curvature. This can then be converted to corneal power using the refractive index of the cornea.

Reflection-based techniques (including keratometry and videokeratoscopy) require a smooth corneal surface and in fact measure the anterior surface of the tear film. Projection-based techniques (including slit images) are able to measure elevation, even in irregular corneas. Scheimpflug-based systems also measure elevation of the corneal surface relative to a reference surface.

Corneal topography has been used to quantify the shape of the normal cornea and its variations and improve our understanding of the relationships between anatomy and function. It can facilitate contact lens fitting, especially in complex cases, and detect contact lens-induced corneal warpage. In corneal disease it can detect subclinical stages, monitor progression and provide measurements prior to surgery. Preoperatively, topography can help plan corneal interventions or intraocular lens implantation. Postoperatively, topography can help with monitoring healing, identifying the cause of visual problems or poor outcomes and planning further interventions (including suture removal) and surgery. Topography is also valuable in communicating with patients and colleagues and maintaining a medicolegal record.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Log in via an institution
Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 99.00
Price excludes VAT (USA)
  • Available as EPUB and PDF
  • Read on any device
  • Instant download
  • Own it forever
Hardcover Book
USD 129.99
Price excludes VAT (USA)
  • Durable hardcover edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

References

*References Particularly Worth Reading

  1. Scheiner C. Occulus Hoc est: fundamentum opticum. Innsbruck: Agricola; 1619.

    Google Scholar 

  2. Placido A. Novo instrumento de esploracao da cornea. Periodico d’Ofthalmologica Practica Lisbon. 1880;5:27–30.

    Google Scholar 

  3. von Helmholtz H. Graefes Arch Ophthalmol. 1854;2:3.

    Google Scholar 

  4. Ambrosio R Jr, Belin MW. Imaging of the cornea: topography vs tomography. J Refract Surg. 2010;26:847–9.

    Article  PubMed  Google Scholar 

  5. Belin MW, Khachikian SS. An introduction to understanding elevation-based topography: how elevation data are displayed – a review. Clin Exp Ophthal. 2009;37:14–29.

    Article  Google Scholar 

  6. Klyce SD, Wilson SE, Kaufman HE. Corneal topography comes of age [editorial]. Refract Corneal Surg. 1989;5:359–61.

    CAS  PubMed  Google Scholar 

  7. Wilson SE, Klyce SD. Advances in the analysis of corneal topography. Surv Ophthalmol. 1991;35:269–77.

    Article  CAS  PubMed  Google Scholar 

  8. Morrow GL, Stein RM. Evaluation of corneal topography: past, present and future trends. Can J Ophthalmol. 1992;27:213–25.

    CAS  PubMed  Google Scholar 

  9. *Roberts C. Corneal topography: a review of terms and concepts. J Cataract Refract Surg. 1996;22:624–629.

    Article  CAS  PubMed  Google Scholar 

  10. *Waring GO. Making sense of keratospeak II: proposed conventional terminology for corneal topography. Refract Corneal Surg. 1989;5:362–367.

    Article  PubMed  Google Scholar 

  11. Klyce SD, Wilson SE. Methods of analysis of corneal topography. Refract Corneal Surg. 1989;5:368–71.

    CAS  PubMed  Google Scholar 

  12. Piñero D, Alio JL, Aleson A, Vergara ME, Miranda M. Corneal volume, pachymetry, and correlation of anterior and posterior corneal shape in subclinical and different stages of clinical keratoconus. J Cataract Refract Surg. 2010;36(5):814–25.

    Article  PubMed  Google Scholar 

  13. Roberts C. Characterisation of the inherent error in a spherically-biased corneal topography system in mapping a radially aspheric surface. J Refract Corneal Surg. 1994;10:103–11.

    Article  CAS  PubMed  Google Scholar 

  14. Klein SA, Mandell RB. Axial and instantaneous power conversion in corneal topography. Invest Ophthalmol Vis Sci. 1995;36:2155–9.

    CAS  PubMed  Google Scholar 

  15. Klein SA, Mandell RB. Shape and refractive powers in corneal topography. Invest Ophthalmol Vis Sci. 1995;36:2096–109.

    CAS  PubMed  Google Scholar 

  16. Cohen KL, Tripoli NK, Holmgren DE, Coggins JM. Assessment of the power and height of radial aspheres reported by computer-assisted keratoscopy. Am J Ophthalmol. 1995;119:723–32.

    Article  CAS  PubMed  Google Scholar 

  17. Eryildirim A, Ozkan T, Eryildirim S, Kaynak S, Cingil G. Improving estimation of corneal refractive power by measuring the posterior curvature of the cornea. J Cataract Refract Surg. 1994;20:129–31.

    Article  CAS  PubMed  Google Scholar 

  18. Patel S, Marshall J, Fitzke FW. Shape and radius of posterior corneal surface. Refract Corneal Surg. 1993;9:173–81.

    CAS  PubMed  Google Scholar 

  19. Gullstrand A. (1911). In: Southall JPC, editor. Helmholtz’s treatise in physiological optics volumes I and II (Appendix). New York: Dover; 1962.

    Google Scholar 

  20. Use of the keratometer. In: Bennett AG, editors. Optics of contact lenses. London: ADO publishing; 1974.

    Google Scholar 

  21. Arffa RC, Klyce SD, Busin M. Keratometry in epikeratophakia. J Refract Surg. 1989;2:61–4.

    Article  Google Scholar 

  22. Patel S. Refractive index of the mammalian cornea and its influence on pachymetry. Ophthalmic Physiol Opt. 1980;7:503–6.

    Article  Google Scholar 

  23. Roberts C. The accuracy of ‘power’ maps to display curvature data in corneal topography. Invest Ophthalmol Vis Sci. 1994;35:3525–32.

    CAS  PubMed  Google Scholar 

  24. *Mandell RB. Corneal power correction factor for photorefractive keratectomy. J Cataract Refract Surg 1994;10:125–128.

    CAS  Google Scholar 

  25. Corbett MC, Verma S, Prydal JI, Pande M, Oliver KM, Patel S, Marshall J. The contribution of the corneal epithelium to the refractive changes occurring after excimer laser photorefractive keratectomy. Invest Ophthalmol Vis Sci. 1995;36:S2.

    Google Scholar 

  26. Applegate RA, Nuñez R, Buettner J, Howland HC. How accurately can videokeratoscophic systems measure surface elevation? Optom Vis Sci. 1995;72:785–92.

    Article  CAS  PubMed  Google Scholar 

  27. Tripoli NK, Cohen KL, Holmgren DE, Coggins JM. Assessment of radial aspheres by the arc-step algorithm as implemented by the Keratron keratoscope. Am J Ophthalmol. 1995;120:658–64.

    Article  CAS  PubMed  Google Scholar 

  28. Tripoli NK, Cohen KL, Obla P, Coggins JM, Holmgren DE. Height measurement of astigmatic test surfaces by a keratoscope that uses plane geometry surface reconstruction. Am J Ophthalmol. 1996;121:668–76.

    Article  CAS  PubMed  Google Scholar 

  29. Swartz T, Marten L, Wang M. Measuring the cornea: the latest developments in corneal topography. Curr Opin Ophthalmol. 2007;18(4):325–33.

    Article  PubMed  Google Scholar 

  30. Oliveira CM, Ribeiro C, Franco S. Corneal imaging with slit-scanning and Scheimpflug imaging techniques. Clin Exp Optom. 2011;94(1):33–42.

    Article  PubMed  Google Scholar 

  31. Corbett MC, Shilling JS, Holder GE. The assessment of clinical investigations: the Greenwich grading system and its application to electrodiagnostic testing in ophthalmology. Eye. 1995;9(Suppl):59–64.

    PubMed  Google Scholar 

  32. Thornton SP. Clinical evaluation of corneal topography. J Cataract Refract Surg. 1993;19(Suppl):198–202.

    Article  Google Scholar 

  33. McDonnell PJ. Current applications of the corneal modeling system. Refract Corneal Surg. 1991;7:87–91.

    CAS  PubMed  Google Scholar 

  34. Piñero DP, Nieto JC, Lopez-Miguel A. Characterization of corneal structure in keratoconus. J Cataract Refract Surg. 2012;38(12):2167–83.

    Article  PubMed  Google Scholar 

  35. Corbett MC, Shun-Shin GA, Awdry PN. Keratometry using the Goldmann tonometer. Eye. 1993;7:43–6.

    Article  PubMed  Google Scholar 

  36. Zabel RW, Tuft SJ, Fitzke FW, Marshall J. Corneal topography: a new photokeratoscope. Eye. 1989;3:298–301.

    Article  PubMed  Google Scholar 

  37. Ediger MN, Pettit GH, Weiblinger RP. Noninvasive monitoring of excimer laser ablation by time-resolved reflectometry. Refract Corneal Surg. 1993;9:268–75.

    CAS  PubMed  Google Scholar 

  38. Wegener A, Laser-Junga H. Photography of the anterior eye segment according to Scheimpflug’s principle: options and limitations – a review. Clin Exp Ophthalmol. 2009;37(1):144–54.

    Article  PubMed  Google Scholar 

  39. Read SA, Collins MJ, Carney LG, et al. The topography of the central and peripheral cornea. IOVS. 2006;47:1404–15.

    Google Scholar 

  40. Sunderraj P. Clinical comparison of automated and manual keratometry in pre-operative ocular biometry. Eye. 1992;6:60–2.

    Article  PubMed  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Imperial College Healthcare NHS Trust, London, UK

    Melanie Corbett

  2. University Hospital Coventry and Warwickshire, Coventry, UK

    Nicholas Maycock

  3. Manchester, UK

    Emanuel Rosen

  4. Department of Ophthalmology, St. Thomas Hospital, London, UK

    David O’Brart

Authors
  1. Melanie Corbett
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Nicholas Maycock
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Emanuel Rosen
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. David O’Brart
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

Copyright information

© 2019 Springer Nature Switzerland AG

About this chapter

Check for updates. Verify currency and authenticity via CrossMark

Cite this chapter

Corbett, M., Maycock, N., Rosen, E., O’Brart, D. (2019). Assessment of Corneal Shape. In: Corneal Topography. Springer, Cham. https://doi.org/10.1007/978-3-030-10696-6_1

Download citation

  • DOI: https://doi.org/10.1007/978-3-030-10696-6_1

  • Published:

  • Publisher Name: Springer, Cham

  • Print ISBN: 978-3-030-10694-2

  • Online ISBN: 978-3-030-10696-6

  • eBook Packages: MedicineMedicine (R0)

Publish with us

Policies and ethics

Search

Navigation