Introduction: The term glaucoma refers to a group of diseases that have a characteristic optic neuropathy with associated visual field loss in common. Intraocular pressure has been considered to be the only causal factor for glaucoma and the only factor that can be manipulated to alter the course of the disease. But considering high intraocular pressure as the only factor responsible for glaucoma confronts us with two problems. First, measurement methods of intraocular pressure are based on superficial pressure of the cornea, therefore, some factors such as corneal thickness and geometrical errors of measurement are included. Second, risk of glaucoma damage changes by changing scleral thickness and size of the eye globe even with equal intraocular pressures. So, there should be some other factors than pressure, which are responsible for glaucoma. Hypothesis: Here, this hypothesis is proposed: stress is responsible for glaucoma and intraocular pressure is just one of the determinants of stress, whereas stress is also dependent on other factors including radius and thickness of sclera. Stress causes strain and obstruction of retinal vessels. Discussion: In fact, a series of factors together determine whether an individual will be affected with glaucoma or not. These factors include intraocular pressure, scleral thickness, radius of the eye globe, and optic nerve head compliance against increased stress. Our hypothesis can explain the existence of normal-pressure glaucoma. It presents a better method for screening of glaucoma and new modalities for glaucoma treatment.