Entoptic phenomenon following pars plana vitrectomy caused by retained preretinal gel." A patient who underwent pars plana vitrectomy for vitreous floaters is described. At the time of surgery, the posterior hyaloid was avulsed and stripped from the posterior retinal surface. Postoperatively, the patient described filamentous and ""sea-fan"" entoptic phenomena scattered throughout the periaxial vision that were in focus, attached, and ""waving"" with movement that was counter to the direction of gaze pursuit and demonstrated after movement. The authors believe these structures represent vitreous gel retained at the retinal surface, even though the structures could not be demonstrated by optical coherence tomography or indocyanine green staining at later vitrectomy surgery. This case should raise caution when considering vitrectomy surgery that requires posterior hyaloid stripping in patients with good vision."