C-shaped flashes of light in the eye are usually caused by posterior vitreous detachment and retinal tears. The retina is the tissue in the eye that is responsible for sensing optical stimuli, and once the retina is stimulated by other abnormalities, such as pulling or tearing, the patient experiences a flashing sensation in front of the eyes. If the patient presses on the eye, he or she may also feel a white flash in front of the eye. When the eye has a C-shaped flash, it is usually due to incomplete posterior vitreous detachment, where the residual vitreous adheres to the retina and pulls to stimulate the retina, resulting in a flashing sensation. In addition, when a fissure forms in the retina, the retina is torn locally and the patient may also experience flashes of light. If flashes of light are frequent, the patient may have a retinal detachment. It is recommended that patients who experience frequent flashes of light before their eyes should be seen in a hospital to have their condition evaluated and treated according to the doctor’s instructions.