In posterior-segment penetrating injuries, the role of cellular and extracellular structures for the development of fraction retinal detachment is a matter of controversy. With the use of immunofluorescence techniques, we studied the cellular components of intravitreal membranes, with particular attention to the presence of intracellular contractile proteins. Our results demonstrate increasing concentrations of intracellular actin filaments in 12- to 21-day-old membrane specimens at the time when traction retinal detachment is most likely to occur in the rabbit eye. The sequence of events reflects the same process that occurs in the wound-healing response throughout the body. The specialized anatomy of the eye, particularly the vitreoretinal relationship at the vitreous base, accounts for the disastrous consequence of fraction retinal detachment.