Aims This study evaluates ocular biometrics and aqueous humour dynamics (AHD) in healthy Chinese volunteers to determine how the various ocular parameters interact to maintain physiological intraocular pressure (IOP) at all ages.
Methods Sixty-nine volunteers enrolled in this cross-sectional study and were categorised into young (20–30 years) and old (≥50 years) groups. Measurements included IOP, ocular biometrics and AHD. Data were analysed using mixed model with random sampling to account for both eyes from the same individual. Spearman’s rank correlation with bootstrap resampling was used to find associations between parameters.
Results Compared with young subjects, old subjects had significantly (p<0.05) thinner corneas (CCT; 549.7±5.7 vs 530.6±5.3 µm; mean±SEM), shallower anterior chambers (3.14±0.05 vs 2.37±0.05 mm) and slower aqueous flow (Fa; 3.0±0.1 vs 2.7±0.1 µL/min). Uveoscleral outflow slowed (Fu; 1.0±0.2 vs 0.7±0.1) but not significantly. A positive linear association between IOP and episcleral venous pressure was found (young: R2=0.16; old: R2=0.08). Negative correlation between Fa and CCT (R2=0.06) and positive correlation between Fa and outflow facility (R2=0.08) was found in old participants.
Conclusions In the healthy ageing Chinese eye, IOP remains unchanged, while Fa slows, which is counterbalanced by slowing of Fu. Aqueous humour exits the eye preferentially through the trabecular route at all ages. Ageing is also associated with shallowing of the anterior chamber and thinning of the cornea. A slower Fa with lower outflow facility supports existence of autoregulatory mechanisms.
- anterior chamber
- aqueous humour
- ciliary body
- intraocular pressure
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Contributors CBT designed the study, analysed data and edited the paper. SF taught techniques to Drs TG and FW, translated all text and conversations when needed and helped prepare the figures. TG recruited the patients from his clinic and collected the data; FW contributed ideas for the study design and provided space and funding to undertake the study. NM provided the statistical help, prepared figures and wrote the sections related to statistics in the paper; SS contributed greatly to the manuscript preparation and revision.
Competing interests None declared.
Ethics approval Research Ethics Committee, Tenth People’s Hospital of Tongji University, Shanghai, China.
Provenance and peer review Not commissioned; externally peer reviewed.
Correction notice This paper has been amended since it was published Online First. Owing to a scripting error, some of the publisher names in the references were replaced with 'BMJ Publishing Group'. This only affected the full text version, not the PDF. We have since corrected these errors and the correct publishers have been inserted into the references.