Distribution of cup-disc ratio in a Swedish population

Increased cup-disc ratio (CDR) is a hallmark of open-angle glaucoma (OAG), an age-related neurodegenerative disease of significant importance for public health. There are few studies on the distribution of CDR in the Nordic populations.

The distribution of CDR was studied in 749 subjects aged 65-74 years in a population survey in the rural district of Tierp, Sweden, from 1984 to 86. The optic discs were assessed with binocular ophthalmoscopy at a slit lamp. Drawings of the discs were made in the protocol and used for the calculation of vertical CDRs. Odds ratios, adjusted for age and sex, according to Mantel-Haenszel (OR_MH), were determined to estimate predictors of increased CDR, defined as a ratio in the upper quartile. For these analyses, the eye with the most advanced OAG or the highest pressure was chosen. Automated perimetry was used to identify OAG.

The distribution of vertical CDR was fairly close to that of other European-derived populations. The mean CDR was 0.45 in both eyes, with no difference between women and men. An increased ratio was associated with the age ≥70 years, a positive family history of OAG and intraocular pressure ≥20 mmHg. OAG increased the risk 8-fold (OR_MH 8.06; 95% CI 4.12-15.8).

In this study, the distribution of CDR was fairly close to that of other European-derived populations. As expected, OAG increased the risk of having a CDR in the upper quartile. The CDR increased with age.