This prospective observational study investigates the impact of pulsatile versus non-pulsatile cardiopulmonary bypass (CPB) flow on choroidal circulation in diabetic and non-diabetic patients undergoing elective coronary artery bypass grafting (CABG). A total of 104 patients aged 30 to 70 years will be included, with balanced distribution between diabetic and non-diabetic groups. Optical coherence tomography angiography (OCTA) will be performed preoperatively and at 1 month postoperatively to assess changes in choroidal vascularity. The primary objective is to determine whether the type of CPB flow affects choroidal microcirculation, particularly in diabetic patients. The findings may support more individualized perfusion strategies in patients at risk of ocular microvascular impairment.

This prospective observational study aims to investigate the effects of pulsatile and non-pulsatile cardiopulmonary bypass (CPB) flow types on choroidal and retinal microcirculation in diabetic and non-diabetic patients undergoing elective coronary artery bypass graft (CABG) surgery. Previous literature suggests that pulsatile perfusion may enhance end-organ perfusion, but data on ocular microvascular circulation remain scarce, especially in diabetic patients.

A total of 104 patients between the ages of 30 and 70 will be enrolled and divided into four groups based on diabetes status and CPB flow type. Optical coherence tomography angiography (OCTA) will be performed preoperatively and at 1 month postoperatively to measure the choroidal vascularity index (CVI) and other retinal microvascular parameters.The primary outcome is the change in CVI between baseline and 1-month follow-up. Secondary outcomes include retinal microvascular changes and comparative analyses between diabetic and non-diabetic groups.By evaluating the relationship between CPB flow type and ocular perfusion, particularly in patients with longstanding diabetes, this study may provide evidence to support individualized CPB strategies to minimize ocular microvascular compromise in cardiac surgery.

Inclusion Criteria:

1. Age between 30 and 70 years
2. Undergoing elective, first-time coronary artery bypass graft surgery (CABG)
3. Stable metabolic status
4. For diabetic group: history of diabetes mellitus for more than 10 years
5. No significant ocular media opacity (e.g., cataract or vitreous hemorrhage)
6. No tremor or condition interfering with OCTA imaging
7. Aortic cross-clamp time ≤ 120 minutes

Exclusion Criteria:

1. Age <30 or >70 years
2. Re-do or emergency cardiac surgery
3. Diabetes duration <10 years (for diabetic group)
4. Unstable metabolic state or active infection
5. Presence of significant cataract, vitreous hemorrhage, or tremor
6. Contraindications to OCTA imaging

Patients scheduled for elective coronary artery bypass grafting, including diabetic and non-diabetic individuals, recruited at a single center (Samsun Training and Research Hospital).