This chapter examines the dynamic role of fluids in ocular physiology, emphasizing the importance of fluid mechanics in maintaining intraocular pressure (IOP), and transport. Aqueous humor flows from the posterior to anterior chamber and exits via the trabecular meshwork and Schlemm’s canal. Normative IOP ranges from 10 to 21 mmHg, and flow velocities in the anterior chamber average 0.1–0.5 mm/s. Resistance to outflow is a central factor in glaucoma pathophysiology. The vitreous humor influences intraocular mechanics and serves as a medium for cellular and molecular transport. Retinal blood flow averages 40–60 mL/100 g/min. Advanced techniques such as OCT, flow cytometry, PCR, and mass spectrometry allow precise analysis of particulate matter in ocular fluids. Beyond the aqueous and vitreous humors, other fluid compartments such as tears, ciliary body secretions, ocular lymphatics, subretinal fluid, and perilymph contribute to ocular and visual homeostasis. Collectively, these fluids form an integrated system crucial to vision.