Open angle glaucoma usually develops with the atrial angle remaining open. This is generally thought to be caused by a lesion in the trabecular tissue that results in increased resistance to outflow of atrial fluid. The resistance to outflow of aqueous humor is impeded because the endothelial mesh of the trabecular meshwork becomes smaller due to various reasons, or because lesions in the post-trabecular tissues lead to elevated superficial scleral venous pressure, or because of the dysregulation of intraocular pressure by the brain center. The resultant poor drainage of atrial fluid leads to pathologically elevated intraocular pressure and typical atrophy of the optic nerve. The disease may also be associated with metabolic diseases, myopia, stress, anxiety, depression, etc. as well, with some familial predisposition. Unlike closed-angle glaucoma, the disease has an insidious onset and often has no obvious self-conscious symptoms, so it is often detected during routine ophthalmologic examinations or health checkups.