The COMS Grading Scheme: Graded Features
White lines along the edges of the arterial or venous blood column (sheathing) or complete opacification of the venous wall (“white threads”) are the abnormalities graded. The total length of vessels involved by either appearance is graded. Sheathing is not graded within 500 microns of the optic disc. Sheathing is to exceed the minimal sheathing standard to be graded as present.
|None: not present|
Mild: less than 1000 microns (minimum standard photograph)
|Moderate: more than 1000 microns, but less than 3000 microns|
|Severe: more than 3000 microns|
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