Abstract
Purpose :
Elevated intraocular pressure (IOP) is a major risk factor for open angle glaucoma (OAG). During each heartbeat, IOP exhibits pulsations described as ocular pulse amplitude (OPA). OPA has been shown to be relevant in glaucoma as IOP and OPA are affected by several factors, including systolic and diastolic blood pressure (SBP, DBP), tissue biomechanics, and aqueous humor (AH) flow. Here, we use a mathematical model to investigate how IOP and OPA are influenced by variations in SBP, DBP, and model parameters characterizing tissue biomechanics and AH flow in comparison with clinical data.
Methods :
The model calculates IOP and OPA from the balance between AH inflow and outflow, the pulsatile BP inputs, and the deformability of ocular tissues. Two simulation scenarios are considered (health and disease), with the latter characterized by an outflow facility reduced by 70% with respect to baseline. In both scenarios, physiological variations are included in SBP and DBP as normal distributions [SBP∼ N (124.1, 11.1) and DBP ∼ N (77.5, 7.1)].
Variations in all other model parameters were assumed to follow a uniform distribution [± 15% with respect to published baseline values (Szopos et al 2016, Stefanoni et al 2018)].
Results :
The table in Fig.1 compares model predictions for IOP and OPA with clinical data on 90 healthy subjects (Cheng et al, 2017) and 115 glaucoma patients. In both health and disease, model results are within the same range of clinical data. Fig. 2 shows the scatterplots of OPA versus pulse pressure (PP=SBP-DBP) as computed by the model (a) and measured clinically (b) on glaucoma patients. When fitted with a linear regression, both computed and measured data had a positive slope of 0.0265 and 0.0122, respectively.
Conclusions :
The model proved capable of simulating IOP and OPA in health and disease. OPA was predicted to increase with PP as evidenced by clinical data on glaucoma patients. These data suggest mathematical modeling approaches may help clinicians confirm and/or discriminate OAG disease.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.