The Distribution of Vertical Cup-to-Disc Ratio and its Determinants in the Iranian Adult Population
1Noor Research Center for Ophthalmic Epidemiology, Noor Eye Hospital, Tehran, Iran.
2Noor Ophthalmology Research Center, Noor Eye Hospital, Tehran, Iran.
3Department of Medical Surgical Nursing, School of Nursing and Midwifery, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
4Ophthalmic Epidemiology Research Center, Shahroud University of Medical Sciences, Shahroud, Iran.
5Refractive Errors Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.
6Department of Epidemiology and Biostatistics, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran.
Purpose: To determine the distribution of vertical cup-to-disc ratio (VCDR) and its relationship with ocular biometric indices.
Methods: This study was conducted in 4737 individuals aged 45-69 years living in Shahroud who participated in the second phase of Shahroud Eye Cohort Study in 2014. All participants underwent eye examinations including the measurement of visual acuity and refraction, slit-lamp biomicroscopy, retinal examination, and fundoscopy. Normality index was used to describe data distribution, and a multiple beta regression, with adjustment for the effect of cluster sampling, was applied to explore the relationship between VCDR and the study variables.
Results: The mean [95% confidence interval (CI)] VCDR was 0.297 (0.293-0.301) in all participants; 0.296 (0.291-0.302) in men and 0.297 (0.292-0.302) in women. The highest mean VCDR was seen in the age group 55-59 years (0.299, 95% CI: 0.292-0.307). The 97.5th percentile was 0.600. According to multiple beta regression analysis, VCDR had a positive association with the female sex (P = 0.028), spherical equivalent (P < 0.001), cigarette smoking (P = 0.020), and axial length (P < 0.001), and had a negative association with hypertension (P = 0.001), best corrected visual acuity (P < 0.001), hyperlipidemia (P = 0.029) and anterior chamber depth (P = 0.001).
Conclusions: The mean VCDR and the 97.5th percentile were lower than most other studies. Although ethnicity and race may play a role in this difference, this difference should be considered in clinical decisions in the current population.
Keywords: Cohort study; Glaucoma; Optical coherence tomography; Vertical cup-to-disc ratio.