What CDR is suspicious for glaucoma?

CDR >=0.7 vertical is suspicious for glaucoma. CDR >0.8 is definitely abnormal. Intereye asymmetry >0.2 is suspicious regardless of absolute CDR. CDR must be correlated with disc size (physiologically large cup in large discs is normal).

How is CDR estimated on fundoscopy?

CDR = vertical cup diameter / vertical disc diameter. Assess with slit-lamp biomicroscopy (78D or 90D lens) or fundus photography. OCT optic nerve head analysis provides objective, reproducible measurements.

What is the ISNT rule for optic nerve assessment?

ISNT rule: normal optic nerve rim tissue should be thickest Inferiorly, then Superiorly, then Nasally, then Temporally (ISNT). Violation of ISNT rule (especially inferior thinning) suggests focal rim loss from glaucoma.

CDR Cup-to-Disc Ratio Significance

Assess glaucomatous optic nerve damage using vertical cup-to-disc ratio (CDR). CDR >=0.7 or asymmetry >0.2 between eyes warrants glaucoma evaluation. Correlate with RNFL thickness and VF.

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CDR Cup-to-Disc Ratio Significance

Frequently Asked Questions

What CDR is suspicious for glaucoma?

How is CDR estimated on fundoscopy?

What is the ISNT rule for optic nerve assessment?