There are two main categories: 1. Foramen ovale detachment Most retinal detachments are of this type. The retinal detachment is caused by various internal and external causes that have produced a fissure in the retina. Internal causes are the causes of the retina itself, such as: high myopia retinal thinning and degeneration, which spontaneously produces a fissure; or vitreous aging produces spontaneous vitreous and retinal separation, which pulls the retina to form a fissure. External causes have eye trauma, and the force out travels to the retina and tears it. 2.Non-porous retinal detachment A few retinal detachments do not have fissures, including: exudative retinal detachment and retinal detachment by pulling. Exudative: common in uveitis, especially in Koyasu-Harada disease, due to choroidal inflammation causing a large amount of exudate to collect under the retina, resulting in detachment. Retraction: Commonly seen in cases of diabetic retinopathy and vitreous accumulation of blood that has not been absorbed for a long time. Due to the formation of fibrous strips within the vitreous with one end adhering to the retina, the fibers contract and produce a pulling force on the retina, pulling it up.