Relationship between cup-disc ratio and optic disc diameter: the Blue Mountains Eye Study

Area of Science:

• Ophthalmology
• Optometry
• Public Health

Background:

• The optic disc's size is a key anatomical feature.
• The vertical cup-to-disc ratio is a critical parameter in glaucoma assessment.
• Understanding normative values is essential for differentiating disease from anatomical variation.

Purpose of the Study:

• To investigate the relationship between optic disc diameter and vertical cup-to-disc ratio.
• To assess this relationship in a population free from glaucoma and optic nerve disease.
• To establish normative data for optic disc parameters in older adults.

Main Methods:

• A cross-sectional study of 3654 individuals aged 49 years and older.
• Data collected in the Blue Mountains region of Sydney, Australia.
• Standardized optic disc photography and corrected magnification effects were utilized.

Main Results:

• The mean vertical optic disc diameter was 1.51 mm.
• The mean vertical cup-to-disc ratio was 0.43.
• A significant positive correlation was found: vertical cup-to-disc ratio increased by 0.270 per mm increase in vertical disc diameter.

Conclusions:

• Vertical optic disc diameter and vertical cup-to-disc ratio exhibit near-normal distribution in older Australians.
• Larger vertical optic disc diameters are consistently associated with larger vertical cup-to-disc ratios.
• These findings contribute to understanding normal optic disc morphology and its variability.