June 1998
Volume 39, Issue 7
Articles  |   June 1998
Circumcorneal annulus of collagen fibrils in the human limbus.
Author Affiliations
  • R H Newton
    The Open University, The Oxford Research Unit, United Kingdom.
  • K M Meek
    The Open University, The Oxford Research Unit, United Kingdom.
Investigative Ophthalmology & Visual Science June 1998, Vol.39, 1125-1134. doi:
  • Views
  • PDF
  • Share
  • Tools
    • Alerts
      This feature is available to authenticated users only.
      Sign In or Create an Account ×
    • Get Citation

      R H Newton, K M Meek; Circumcorneal annulus of collagen fibrils in the human limbus.. Invest. Ophthalmol. Vis. Sci. 1998;39(7):1125-1134.

      Download citation file:

      © ARVO (1962-2015); The Authors (2016-present)

  • Supplements
This content is PDF only. Please click on the PDF icon to access.

PURPOSE: To quantify the orientation of the collagen fibrils in the human limbus and to compare it with the orientation in the cornea and the sclera. METHODS: Fibril orientation was measured from 100 synchrotron x-ray diffraction patterns collected at intervals along lines across the cornea, limbus, and sclera. RESULTS: A distinct circumcorneal annulus of collagen fibrils was revealed in the limbus. For the individual cornea investigated, the annulus was not uniform around the corneal circumference; its width, fibril angular spread, and fibril density all varied with position. The average width of the annulus was narrower in the superior sector (1.5 mm) than in the inferior sector (2.0 mm). The results from the edge of the cornea suggested that the preferentially aligned corneal fibrils bend sharply at the limbus to run circumferentially or that, together with this bending or alone, extra fibrils arising in the sclera run across this zone. In the cornea the biaxial preferred directions became more pronounced from the center of the cornea toward the limbus along the superior-inferior axis. CONCLUSIONS: The excess of circumferential fibrils in the limbus, predicted from the sharp change of curvature in the surface of the eye at the limbus, appeared to take the form of a well-defined annulus. From a consideration of the mechanics of the system it seemed probable that the purpose of this annulus was to help maintain the correct curvature of the cornea. Before further research, it was hypothesized that some refractive problems associated with an incorrect curvature of the cornea may be related in part to abnormalities of this circumcorneal annulus.


This PDF is available to Subscribers Only

Sign in or purchase a subscription to access this content. ×

You must be signed into an individual account to use this feature.