PURPOSE: To quantify the orientation of the collagen fibrils in the @entity1 limbus and to compare it with the orientation in the @entity5692 . METHODS: Fibril orientation was measured from 100 synchrotron x-ray diffraction patterns collected at intervals along lines across the @entity267 , limbus, and sclera. RESULTS: A distinct circumcorneal annulus of collagen fibrils was revealed in the limbus. For the individual @entity267 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 @entity267 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 @entity267 the biaxial preferred directions became more pronounced from the center of the @entity267 toward the limbus along the superior-inferior @entity2270 . 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 @entity267 . Before further research, it was hypothesized that some refractive problems associated with an incorrect curvature of the @entity267 may be related in @entity854 of this circumcorneal annulus.

Circumcorneal annulus of collagen fibrils in the XXXX limbus.

@entity1 :: ('9606', 'Species') :: ['human'] @entity267 :: ('MESH:D065306', 'Disease') :: ['cornea'] @entity854 :: ('MESH:D018376', 'Disease') :: ['part to abnormalities'] @entity2270 :: ('MESH:C566610', 'Disease') :: ['axis'] @entity5692 :: ('MESH:D015422', 'Disease') :: ['cornea and the sclera']
@entity1 :: (9606,Species) :: ['human']
