Distribution of cup-disc ratio in a Swedish population.

Background: 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.

Methods: 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.

Results: 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).

Conclusions: 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.