Purpose :
High intraocular pressure (IOP) and low systolic and diastolic blood pressures (SP and DP) lead to low perfusion pressure and are considered risk factors for glaucoma. Diastole is the low-pressure part of the cardiac cycle and is likely to be more prone to low perfusion. In this study, we investigate how diastolic hemodynamics change in the central retinal artery and vein (CRA and CRV) as a function of SP, DP and IOP.

Methods : A validated mathematical model (Guidoboni et al, 2014) is used to simulate retinal circulation. A sensitivity analysis is performed to quantify variations in the diastolic flux and vascular resistances in the CRA and CRV (DQcra, DQcrv, DRcra and DRcrv) resulting from variations in SP, DP and IOP, whose distributions are based on data on ocular hypertensive subjects (IOP > 21mmHg) from the Singapore Epidemiology of Eye Diseases Study (Tham et al, 2017), see Fig1[A-C]. The fraction of total output variance associated with a given input when it varies singly or jointly with all the input set is given by the first and total Sobol indices, respectively.

Results : Fig1[D-E] shows the computed distribution of DRcra and DRcrv, while Fig2[A-D] reports the computed Sobol indices . Model results indicate that: (i) the distributions of DQcra and DQcrv are very similar and both follow a normal distribution (N~(2.10e-4, 9.98e-09) , N~(1.78e-4 ± 1.08e-8 ml/s), pvalue < 0.001)(ii) DRcra fits a normal distribution (N~(953,31)), while DRcrv exhibits a skewed and more spread distribution (median = 20207 mmHg s cm3 , mean = 32070 mmHg s cm3); (iii) DQcra and DQcrv present a similar dependency on SP, DP and IOP; (iv) DRcra mainly depends on SP and DP, while DRcrv, depends entirely on IOP.

Conclusions : Results from our model predict that DRcra is mainly controlled by SP and DP, while DRcrv is mainly controlled by IOP. Furthermore, different vascular resistance properties in the CRA and CRV result in a similar response in their diastolic flux. These results may provide insight into why high IOP and low SP and DP are risk factors for glaucoma.