Ophthalmoscopic estimation of cup‐to‐disc ratio and its relation to the evening intraocular pressure in normal individuals

Abstract

Purpose: To record and relate the cap‐to‐disc ratio (C/D ratio), as assessed by ophthalmoscopy and the evening intraocular pressure (IOP) of normal individuals of various age groups. Methods: 467 normal individuals, randomly selected, were examined by the same experienced ophthalmologist. The C/D ratio was assessed by ophthalmoscopy and the IOP was measured in the evening by Applanation Tonometry. The individuals were divided into three age groups (Group A: 120 individuals 20‐40 years old, Group B: 233 individuals 41‐60 years old, Group C: 114 individuals 61‐80 years old). Results: Group A: C/D ratio ranged from 0 to 0.9 (mean±SD 0.496±0.221) and IOP ranged from 8 to 22 mmHg (mean±SD 13.35±2.650 mmHg). Group B: C/D ratio ranged from 0 to 0.85 (mean±SD 0.452±0.212) and IOP ranged from 8 to 22 mmHg (mean ± SD 14.079 ± 2.781 mmHg). Group C: C/D ratio ranged from 0 to 0.85 (mean±SD 0.499±0.221) and IOP ranged from 10 to 20 mmHg (mean±SD 14.133±2.419 mmHg). The relation (r) between IOP and C/D ratio was as follows: Group A: r = 0.268 (p<0.001), Group B: r = 0.063 (p<0.001), Group C: r = 0.109 (p<0.001). Conclusions: The C/D ratio values were, in general, larger in individuals with higher IOP values. However, this relation was weak though statistically significant. In Group B the relation was of lower statistical significance than in the Group A and in the Group C. This weak relation is possibly indicative that other factors except for IOP contribute to the final C/D ratio of normal individuals. There are individuals with high C/D ratios and relatively low IOP values and vice versa. The examiner is responsible for identifying cases which should undergo further investigation.