Some vitreoretinal diseases require surgical treatment. In some cases, such as retinal detachment and macular hole, surgery must be performed as soon as possible. In other situations, such as macular pucker (a membrane that curls up the retina) and vitreous hemorrhage (sudden hemorrhage within the eye), surgery can be scheduled with less urgency. Vitreoretinal surgery is a highly specialized microsurgical procedure performed on an outpatient basis under local anesthesia. The symptoms of a vitreoretinal disease requiring surgery are various, ranging from sudden vision loss, to distorted vision, to the sudden appearance of floaters in the visual field. An ophthalmologist will evaluate each individual case and make the diagnosis. A medical or surgical treatment will follow. A timely eye examination is essential; a delay in diagnosis can irreversibly compromise vision.