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Assessment of Corneal Shape

  • Melanie Corbett
  • Nicholas Maycock
  • Emanuel Rosen
  • David O’Brart
Chapter

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.

Keywords

Corneal topography Corneal shape Corneal elevation Corneal curvature Corneal power Videokeratoscopy Scheimpflug 

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Copyright information

© Springer Nature Switzerland AG 2019

Authors and Affiliations

  • Melanie Corbett
    • 1
  • Nicholas Maycock
    • 2
  • Emanuel Rosen
    • 3
  • David O’Brart
    • 4
  1. 1.Imperial College Healthcare NHS TrustLondonUK
  2. 2.University Hospital Coventry and WarwickshireCoventryUK
  3. 3.ManchesterUK
  4. 4.Department of OphthalmologySt. Thomas HospitalLondonUK

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