AQP4 and ischemia: Therefore, we assume that osmotic pressure, oxygen concentration, hormones, neurotransmitters, cytokines, and other factors affect the expression of AQP4 through cGMP/PKG, MAPK [23], and other signaling pathways, thereby affecting the blood-retinal barrier and active transfer of water, K+, etc., leading to the formation of ischemia and edema in patients with diabetic retinopathy.