Age-Related Reductions in Retinal Vessel Density Partly Reflect Vessel Calibre: A Two-Centre Fundus Imaging Study

Mohd Zulfaezal Che Azemin; Mohd Izzuddin Mohd Tamrin; Adzura Salam; Firdaus Yusof; Edre Mohammad Aidid; Ahmed M Y Osman; Iqbal Jamaludin

doi:10.33102/mjosht.593

Authors

Mohd Zulfaezal Che Azemin Integrated Omics Research Group, Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Kampus Kuantan, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang, Malaysia.
Mohd Izzuddin Mohd Tamrin Kulliyyah of ICT, International Islamic University Malaysia, Jalan Gombak, 53100 Kuala Lumpur, Malaysia.
Adzura Salam Kulliyyah of Medicine, International Islamic University Malaysia, Kampus Kuantan, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang, Malaysia.
Firdaus Yusof Integrated Omics Research Group, Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Kampus Kuantan, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang, Malaysia.
Edre Mohammad Aidid Kulliyyah of Medicine, International Islamic University Malaysia, Kampus Kuantan, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang, Malaysia.
Ahmed M Y Osman Kulliyyah of Pharmacy, International Islamic University Malaysia, Kampus Kuantan, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang, Malaysia.
Iqbal Jamaludin Integrated Omics Research Group, Kulliyyah of Allied Health Sciences, International Islamic University Malaysia, Kampus Kuantan, Jalan Sultan Ahmad Shah, 25200 Kuantan, Pahang, Malaysia.

DOI:

https://doi.org/10.33102/mjosht.593

Keywords:

ageing, fundus photography, retinal vessel calibre, vessel density

Abstract

Purpose: To examine relationships among age, retinal vessel calibre, and vessel density, and determine whether arterial and venous calibre statistically account for part of the association between age and corresponding vessel density. Materials and Methods: This retrospective cross-sectional study included 384 eligible right-eye colour fundus image records from two clinical centres. Retinal vascular measurements were obtained using AutoMorph. Composite scores were derived for arterial and venous calibre and vessel density using measurements from the full analysed field and standard retinal zones. A parallel partial-mediation model evaluated arterial and venous pathways simultaneously, adjusting for sex, centre, and age-by-centre interaction. Indirect effects were assessed using 2,000 centre-stratified bootstrap resamples. Results: Mean age was 40.54 ± 16.13 years; 159 records (41.4%) were male. Older age was associated with smaller arterial (β = −0.531) and venous calibre (β = −0.413; both P < 0.001). Larger calibre was associated with greater corresponding vessel density (arterial β = 0.267; venous β = 0.356; both P < 0.001). Age remained directly associated with lower arterial (β = −0.211) and venous density (β = −0.241; both P < 0.001). Indirect effects through arterial and venous calibre were −0.142 (95% CI, −0.183 to −0.100) and −0.147 (95% CI, −0.191 to −0.105), accounting statistically for 40.2% and 38.0% of the respective total associations. Conclusions: Retinal vessel calibre accounted statistically for approximately two-fifths of the association between older age and lower arterial and venous vessel density, while substantial direct age associations remained. These findings demonstrate that age-related reductions in area-based retinal vessel density cannot be interpreted as vascular rarefaction alone, because vessel width contributes directly to the segmented vascular area. The indirect effects therefore represent statistical decomposition rather than evidence of causal mediation. Joint assessment of vessel calibre, density, and vascular complexity may provide a more informative characterisation of retinal vascular ageing.

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