PURPOSE: To determine the relationship between axial length (AL), retinal function, and relative oxygen (O₂) consumption to better understand the protective effect of axial elongation on diabetic retinopathy development. METHODS: Measurements of AL, multifocal electroretinogram (mfERG), and relative O₂ consumption (difference between arteriolar and venular O₂ saturation levels or A-V difference) were performed on 50 healthy individuals. The relationships between AL, mfERG amplitude, and A-V difference were analyzed using linear regression models. Path analysis was performed to determine the direct and indirect effects (via mfERG amplitude) of AL on A-V difference. RESULTS: mfERG P1 amplitude was positively associated with A-V difference (β = 0.33; 95% confidence interval [CI]: 0.23-0.42). Increased AL was significantly associated with a decrease in A-V difference (β = -1.08; 95% CI: -1.52 to -0.65) as well as a decrease in retinal function (β = -3.14, 95% CI: -4.07 to -2.20). Path analysis models including AL (study factor), retinal function (intermediate variable), and A-V difference (outcome variable) showed that AL had little direct association with A-V difference (β(p) = -0.002), while the indirect effect of AL on A-V difference via changes in retinal function were substantial (β(p) = -0.51). CONCLUSIONS: In eyes with longer AL, the reduction in A-V difference is explained by the parallel reduction in retinal function. These findings suggest that longer eyes have decreased retinal function and O₂ consumption, and thus are relatively less hypoxic in the presence of diabetes, which may partly explain the reduced risk of DR in these eyes.
PURPOSE: To determine the relationship between axial length (AL), retinal function, and relative oxygen (O₂) consumption to better understand the protective effect of axial elongation on diabetic retinopathy development. METHODS: Measurements of AL, multifocal electroretinogram (mfERG), and relative O₂ consumption (difference between arteriolar and venular O₂ saturation levels or A-V difference) were performed on 50 healthy individuals. The relationships between AL, mfERG amplitude, and A-V difference were analyzed using linear regression models. Path analysis was performed to determine the direct and indirect effects (via mfERG amplitude) of AL on A-V difference. RESULTS: mfERG P1 amplitude was positively associated with A-V difference (β = 0.33; 95% confidence interval [CI]: 0.23-0.42). Increased AL was significantly associated with a decrease in A-V difference (β = -1.08; 95% CI: -1.52 to -0.65) as well as a decrease in retinal function (β = -3.14, 95% CI: -4.07 to -2.20). Path analysis models including AL (study factor), retinal function (intermediate variable), and A-V difference (outcome variable) showed that AL had little direct association with A-V difference (β(p) = -0.002), while the indirect effect of AL on A-V difference via changes in retinal function were substantial (β(p) = -0.51). CONCLUSIONS: In eyes with longer AL, the reduction in A-V difference is explained by the parallel reduction in retinal function. These findings suggest that longer eyes have decreased retinal function and O₂ consumption, and thus are relatively less hypoxic in the presence of diabetes, which may partly explain the reduced risk of DR in these eyes.