Glaucoma disc features
0.30
0.40
0.50
0.60
0.70
Disc haemorrhage
0.80
0.8
0.90
Bayonetting &
vessel baring
Notch
Beta zone atrophy
Bayonetting
Beta
zone
Vessel baring
Alpha
zone
99th %
95th %
50th %
0.65
0.56
0.35
1.3mm
0.67
0.61
0.39
1.4mm
0.70
0.63
0.42
1.5mm
0.71
0.65
0.45
1.6mm
0.75
0.68
0.50
1.7mm
0.78
0.69
0.52
1.8mm
0.83
0.74
0.55
1.9mm
Crowston, J G et al. “The effect of optic disc diameter on vertical cup to disc ratio percentiles in a population based cohort: the Blue Mountains Eye Study.”
The British Journal of Ophthalmology vol. 88,6 (2004): 766-70. doi:10.1136/bjo.2003.028548
As the likelihood of normality decreases the level of suspicion should increase.
Accompanying OT
Skills guide video
C:D ratios at the 50th percentile are likely to be normal. At the 95th percentile there are very few normal optic discs with C:D ratios at this
level. At the 99th percentile only 1% of non-glaucomatous eyes have a C:D ratio of this size.
Data represents the spread of C:D ratios found in various optic nerve sizes excluding eyes with glaucoma.
0.62
0.56
0.33
1.2mm
Vertical disc diameter (mm)