Relationship between proliferative diabetic retinopathy and ophthalmodynamometric pressure measured during pars plana vitrectomy surgery

Abstract

The evaluation of intraocular pressure (IOP) at the onset of optic disc pulsation (ODP) serves as a vital indicator of ocular perfusion, particularly in patients with retinal vascular diseases. Understanding the relationship between ODP and systemic hemodynamic parameters, such as mean blood pressure (MAP), is crucial for predicting both retinal and systemic circulatory dynamics. Previous studies have demonstrated a significant correlation between ODP and MAP, suggesting that ODP may reflect broader vascular conditions beyond the eye. This study aims to investigate ODP measurements during pars plana vitrectomy in patients with proliferative diabetic retinopathy compared to a control group with non-diabetic retinal vascular diseaase, emphasizing the potential of ODP as a clinical tool for assessing retinal and systemic vascular health. Methods: This cross sectional study, conducted from June 2023 to June 2024 at Nikookari Hospital in Tabriz, evaluated ODP during pars plana vitrectomy (PPV) in two patient groups: those with proliferative diabetic retinopathy (PDR) and a control group undergoing PPV for other reasons, such as rhegmatogenous retinal detachment, macular hole, or idiopathic epiretinal membrane (ERM). Based on previous studies indicating a mean ODP of 63.8 mmHg in diabetic eyes and 71.9 mmHg in non-diabetic eyes (δ = 8.1, σ = 12 mmHg), with an alpha of 5% and a power of 80%, the sample size was determined to be 35 patients per group. ODP was measured during surgery using vented-gas forced infusion (VGFI) by gradually increasing intraocular pressure until pulsation was observed in the central retinal artery, repeating the process three times and averaging the results. MAP was calculated simultaneously. Results: This study analyzed 70 eyes, equally divided between the PDR and non-DR groups. The PDR group had a mean age of 60 ± 8.4 years, 21 females, and 14 males, while the non-DR group had a mean age of 61 ± 15.2 years, with 16 females and 19 males. The mean BMI in the PDR group was higher (28 ± 3.2 kg/m²) compared to the non-DR group (26 ± 5.3 kg/m²). The mean arterial pressure (MAP) in the PDR group was 92 ± 12.4 mmHg, higher than in the non-DR group (87 ± 14.7 mmHg). Additionally, the ODP was significantly higher in the PDR group (55 ± 9.6 mmHg) compared to the non-DR group (47 ± 9.3 mmHg), with a mean difference of 8.2 mmHg (p-value < 0.001), indicating a moderate to large effect size (Cohen’s d = 0.86; 95% CI: [0.37-1.35]). Pearson's correlation showed no significant linear relationship between MAP and ODP in the PDR group (r = 0.1; 95% CI: [-0.24, 0.42]), while a moderate to strong correlation was observed in the non-DR group (r = 0.53; 95% CI: [0.24, 0.74]).