Retinal detachment (RD) represents a common yet sight-threatening condition, if left untreated. Rhegmatogeneous retinal detachment (RRD) is the most common type of RD and it happens when a tear or hole forms in the retina, allowing liquefied vitreous to enter into the subretinal space progressively detaching the retina. The motion of the vitreous humor is known to have an effect on RD progression; however, its effect is not yet fully understood. This work presents a three-dimensional fluid-structure interaction (FSI) computer simulation to assess the hydrodynamic forces acting on retinal tears during saccadic eye movements. Using a realistic eye geometry derived from the literature, we simulate the dynamics of liquified vitreous within the vitreous chamber and its interaction with the retinal flap characteristic of RRD. The FSI simulations are performed using a validated in-house solver that couples the fluid dynamics of the vitreous humor with the structural response of the retinal tissue. During rapid saccadic movements, significant hydrodynamic forces are generated within the vitreous cavity, potentially exacerbating RD. In addition to computing the entire three-dimensional velocity and pressure fields within the vitreous, we evaluate the adhesion energy required to prevent tear propagation and further RD. This analysis enables assessment of how certain anatomical positions of the retinal holes---such as those posterior to the equator of the eye---are at higher risk of detachment progression from a fluid-dynamics standpoint. The methodology represents a forward step toward digital twin applications in ophthalmology, where numerical simulations could help understand the evolution of pathologies and optimize surgical planning for RD prevention.