Aging affects retinal oxygen and blood flow metrics in mice

Aging affects the eyes and is a major risk factor for ocular diseases. The purpose of this study was to determine the effect of age on retinal oxygen and blood flow metrics in mice.

Forty-seven C57BL/6 mice were included in four age groups (3-month-old (m): N = 18, 9m: N = 13, 15m: N = 8, and 21m: N = 8). Retinal arterial and venous diameters (D_A, D_V), venous blood velocity (V_V), and arterial and venous oxygen contents (O_2A, O_2V) were measured by our established multimodal imaging system. Average blood flow (BF), oxygen delivery (DO₂), metabolism (MO₂), and extraction fraction (OEF) were calculated. ANOVA, and Tukey post-hoc analyses were performed to determine the effect of age on variables.

We found significant differences in V_V, BF, O_2A, O_2V, and DO₂ among the age groups. V_V was significantly lower in the 21m (p = 0.004) and marginally lower in 15m (p = 0.06) compared to the 3m group, representing reductions of 41% and 30%, respectively. BF was lower in the 21m than the 3m group (p = 0.007), a 42% reduction. Additionally, O_2A and O_2V were significantly lower in 21m compared to the 9m group (p ≤ 0.05), indicating reductions of 30% and 65%, respectively. DO₂ was significantly decreased in the 21m compared to 15m (p = 0.05) and 9m (p = 0.04) groups, representing reductions of 46% and 44%, respectively. Differences in MO₂, OEF, D_A, and D_V did not reach statistical significance (p ≥ 0.07).

Our results showed that retinal vascular oxygen content, oxygen delivery rate, and blood flow were significantly reduced in older mice and established baselines for retinal physiological biomarkers according to age.