Intraocular pressure and circumpapillary retinal nerve fibre layer thickness in the Northern Ireland Cohort for the Longitudinal Study of Ageing (NICOLA): distributions and associations.

AIMS: To describe the distributions of and associations with intraocular pressure (IOP) and circumpapillary retinal nerve fibre layer (cRNFL) thickness in a population-based study.

METHODS

Northern Ireland Cohort for the Longitudinal Study of Ageing participants underwent a computer-assisted personal interview, a self-completion questionnaire and a health assessment (HA). At the HA, participants underwent IOP measurement using Ocular Response Analyser and spectral-domain optical coherence tomography with Heidelberg Spectralis. Participants also underwent a range of anthropometric, ophthalmic, cardiovascular, cognition and blood tests. Participants who attended the HA and had a vertical cup-to-disc ratio (VCDR) measurement in at least one eye were eligible for the study. Participants without any IOP or cRNFL measurements were excluded from the respective analyses.

RESULTS

There were 3221 participants eligible for this study (5753 eyes included in the IOP analysis and 5461 eyes included in the cRNFL analysis). The mean (SD) Goldmann correlated IOP (IOPg) was 15.39 mm Hg (3.55 mm Hg). The mean (SD) average global cRNFL thickness was 94.39 µm (11.18 µm). Increased IOPg was associated with increased age, male sex, hypertension, refractive error (myopic decrease in spherical equivalent) and increased corneal resistance factor, while beta-blocker drug use was associated with lower IOPg in the fully adjusted multivariate analysis. Thinner average global cRNFL was associated with Alzheimer's disease in the age-adjusted and sex-adjusted model. In the fully adjusted multivariate analysis, increased age, male sex, left eyes, hypertension, increased VCDR, refractive error (myopic decrease in spherical equivalent) and increased IOPg were associated with thinner average global cRNFL, while Parkinson's disease and current (vs never) smoking status were associated with thicker average global cRNFL.

CONCLUSIONS

Increased IOP and reduced cRNFL were associated with increased age, myopic refractive error, male sex and hypertension. Alzheimer's disease was associated with thinner average global cRNFL, while Parkinson's disease was associated with thicker average global cRNFL.