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.

⚕ Clinical Disclaimer: These calculators are for educational and reference purposes only. Always verify results with qualified clinical judgment and current clinical guidelines. Do not use as a sole basis for medical decisions.

How It Works

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

Each component has a specific meaning:

Vertical cup-to-disc ratio — The vertical cup-to-disc ratio recorded for the scenario being assessed.

Note: Interpret the cdr significance result against the thresholds and context described above.

How to Use

Enter the vertical cup-to-disc ratio for the scenario you are assessing. 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. Use the cdr significance result to inform your calculation.