Elsevier

Survey of Ophthalmology

Volume 59, Issue 6, November–December 2014, Pages 599-614
Survey of Ophthalmology

Major Review
Corneal assessment technologies: Current status

https://doi.org/10.1016/j.survophthal.2014.05.001Get rights and content

Abstract

There are now many devices that acquire data about the cornea: shape, power, pachymetry at any desired point of the cornea, corneal hysteresis, flap thickness (in LASIK procedures), endothelial cell count and morphology, and so forth. We review the literature on corneal assessment techniques and devices available in clinical practice. Specifically, we discuss slit lamp biomicroscopy, specular microscopy, ultrasound pachymetry, confocal microscopy, very-high-frequency digital ultrasound biomicroscopy, optical coherence tomography, Placido disk-based keratoscopy, slit-scanning elevation topography, Scheimpflug imaging, and dynamic applanation procedures—all of which can be used to assess the morphology of the cornea. In addition, we present a critical analysis of the instrumentation described and discuss the necessity of developing new technology for assessing both the morphology and the physiology of the cornea.

Section snippets

Corneal morphology

The cornea is the major refractive element of the eye, contributing approximately 43 of the 60 diopters (D) of the eye optical system and accounting for approximately 70% of the total refraction.20 The cornea measures approximately 11 mm vertically and 12 mm horizontally in adults58 (with differences in moderate and high degrees of myopia, which results in lower white-to-white diameters68), and its anterior radius of curvature averages 7.8 mm.20 The cornea is approximately 535 μm thick,25 and

Corneal assessment technologies: Current status

In 1619, Father Christopher Scheiner observed that glass spheres of different radii reflected images of different sizes onto the cornea, and he determined the corneal curvature by matching the size of the images with that produced by the spheres.79 Since then, the biggest advances were made during the 20th century, with the rapid development of new technologies. We review the most important features of the different technologies—from slit-lamp biomicroscopy, first introduced in 1911, to

Discussion

The corneal assessment devices described in this review are among the most common options to clinically assess and evaluate the cornea and the anterior segment of the eye. They are capable of providing a wide range of data: corneal shape, power, pachymetry and hysteresis, flap thickness (after LASIK procedures), epithelial and endothelial cell morphology, and so forth. Moreover, these devices have multiple applications in eye examination and eye disease diagnosis.

It seems that there already

Conclusion

Current corneal assessment technologies make the process of corneal evaluation extremely fast and simple. Despite the significant progress that has been made, the necessity of developing new devices to gain a full understanding of corneal physiology is evident. The SLB is a traditional technique required when performing a correct and complete assessment of the anterior eye anatomy and identifying clinical signs, pathologies or alterations of the cornea. In many cases, however, the different

Method of literature search

We performed an extensive electronic search of the Medline and PubMed databases using individual and combinations of key words (cornea, pachymetry, thickness, epithelium, stroma, endothelium, flap, slit-lamp, biomicroscopy, ultrasound, high-frequency, tomography, specular, confocal, placido, topography, scheimpflug, and microscopy) in December 2013 to identify the relevant publications in this field. We also included additional references (from different sources) that were cited in these

Disclosure

The authors report no proprietary or commercial interest in any product mentioned or concept discussed in this article.

References (121)

  • M.J. Doughty et al.

    Human corneal thickness and its impact on intraocular pressure measures: a review and meta-analysis approach

    Surv Ophthalmol

    (2000)
  • R.C. Drews

    Fundus photography by electronic flash III. A new fundus-anterior segment camera

    Am J Ophthalmol

    (1957)
  • W.J. Dupps et al.

    Multivariate model of refractive shift in Descemet-stripping automated endothe- lial keratoplasty

    J Cataract Refract Surg

    (2008)
  • N. Efron

    Contact lens-induced changes in the anterior eye as observed in vivo with the confocal microscope

    Prog Retin Eye Res

    (2007)
  • J.C. Erie et al.

    Confocal microscopy in ophthalmology

    Am J Ophthalmol

    (2009)
  • D.S. Friedman et al.

    Anterior chamber angle assessment techniques

    Surv Ophthalmol

    (2008)
  • J.R. Hassell et al.

    The molecular basis of corneal transparency

    Exp Eye Res

    (2010)
  • S. Jonuscheit et al.

    Discrepancy between central and midperipheral corneal thickness measurements obtained with slit-scanning pachymetry and noncontact specular microscopy

    J Cataract Refract Surg

    (2009)
  • C. Knupp et al.

    The architecture of the cornea and structural basis of its transparency

    Adv Protein Chem Struct Biol

    (2009)
  • Y. Li et al.

    Pachymetric mapping with Fourier-domain optical coherence tomography

    J Cataract Refract Surg

    (2010)
  • J.J. Lim et al.

    Electrical properties of rabbit corneal endothelium as determined from impedance measurements

    Biophys J

    (1981)
  • Z. Liu et al.

    The effects of long-term contact lens wear on corneal thickness, curvature, and surface regularity

    Ophthalmology

    (2000)
  • D.A. Luce

    Determining in vivo biomechanical properties of the cornea with an ocular response analyzer

    J Cataract Refract Surg

    (2005)
  • R. Martin et al.

    White-to-white corneal diameter differences in moderately and highly myopic eyes: partial coherence interferometry versus scanning-slit topography

    J Cataract Refract Surg

    (2013)
  • R. Martin et al.

    Investigation of posterior corneal curvature in CL-induced corneal swelling

    Cont Lens Anterior Eye

    (2009)
  • J.W. McLaren et al.

    Corneal thickness measurement by confocal microscopy, ultrasound, and scanning slit methods

    Am J Ophthalmol

    (2004)
  • R.L. Niederer et al.

    Clinical in vivo confocal microscopy of the human cornea in health and disease

    Prog Retin Eye Res

    (2010)
  • D.N. Parmar et al.

    Tandem scanning confocal corneal microscopy in the diagnosis of suspected acanthamoeba keratitis

    Ophthalmology

    (2006)
  • C.M. Prospero Ponce et al.

    Central and peripheral corneal thickness measured with optical coherence tomography, scheimpflug imaging, and ultrasound pachymetry in normal, keratoconus-suspect, and post-laser in situ keratomileusis eyes

    J Cataract Refract Surg

    (2009)
  • Y. Qazi et al.

    Corneal transparency: genesis, maintenance and dysfunction

    Brain Res Bull

    (2010)
  • D.Z. Reinstein et al.

    Combined Artemis very high-frequency digital ultrasound-assisted transepithelial phototherapeutic keratectomy and wavefront-guided treatment following multiple corneal refractive procedures

    J Cataract Refract Surg

    (2006)
  • D.Z. Reinstein et al.

    Very high-frequency digital ultrasound biomicroscopy

  • T.M. Almubrad et al.

    Comparison of the precision of the Topcon SP-3000P specular microscope and an ultrasound pachymeter

    Clin Ophthalmol

    (2011)
  • R. Ambrósio et al.

    Evaluation of corneal shape and biomechanics before LASIK

    Int Ophthalmol Clin

    (2011)
  • M. Bald et al.

    Anterior chamber angle evaluation with fourier-domain optical coherence tomography

    J Ophthalmol

    (2012)
  • G. Baum et al.

    The application of ultrasonic locating techniques to ophthalmology. II. Ultrasonic slit-lamp in the ultrasonic visualization of soft tissues

    AMA Arch Ophthalmol

    (1958)
  • M.W. Belin et al.

    An introduction to understanding elevation-based topography: how elevation data are displayed - a review

    Clin Experiment Ophthalmol

    (2009)
  • M.W. Belin et al.

    New technology in corneal imaging

    Int Ophthalmol Clin

    (2010)
  • W.M. Bourne

    Corneal endothelium: past, present, and future

    Eye Contact Lens

    (2010)
  • J. Brody et al.

    Corneal topography: history, technique and clinical uses

    Int Ophthalmol Clin

    (1994)
  • W. Buehl et al.

    Comparison of three methods of measuring corneal thickness and anterior chamber depth

    Am J Ophthalmol

    (2006)
  • H.D. Cavanagh et al.

    Specular microscopy, confocal microscopy, and ultrasound biomicroscopy: diagnostic tools of the past quarter century

    Cornea

    (2000)
  • A. Cheng et al.

    Central corneal thickness measurements by ultrasound, Orbscan II, and Visante OCT after LASIK for myopia

    J Refrac Surg

    (2008)
  • A. Cruzat et al.

    In vivo confocal microscopy of corneal nerves: analysis and clinical correlation

    Semin Ophthalmol

    (2010)
  • J.T. Daniels et al.

    Corneal epithelial stem cells in health and disease

    Stem Cell Rev

    (2006)
  • M.J. Doughty et al.

    The orbscan acoustic (correction) factor for central corneal thickness measures of normal human corneas

    Eye Contact Lens

    (2010)
  • R.C. Drews

    Depth of field in slit image photography. An optical solution using the Scheimpflug principle

    Ophthalmologica

    (1964)
  • N. Efron

    The Glenn A. Fry award lecture 2010: Ophthalmic markers of diabetic neuropathy

    Optom Vis Sci

    (2011)
  • J.G. Flanagan et al.

    Indirect fundus biomicroscopy

    Ophthalmic Physiol Opt

    (1995)
  • D. Gatinel et al.

    Measurement of combined corneal, internal, and total ocular optical quality analysis in anterior segment pathology with the OPD-scan and OPD-station

    J Refract Surg

    (2006)
  • Cited by (77)

    • Diagnostic Instruments

      2023, Contact Lens Practice, Fourth Edition
    View all citing articles on Scopus
    View full text