It is essential to understand the pathophysiology of perforating injuries to determine the timing of primary and secondary repair. The foundation of our current understanding of the natural history of posterior segment globe injuries stems from rhesus monkey studies by Cleary and Ryan 30 years ago. They created 8 mm pars plana incisions and prolapsed vitreous, which was cut and removed. The wound was then surgically closed, and autologous blood was injected into the globe. Posterior vitreous detachments (PVD) usually occurred at 1 to 2 weeks. Peripheral tractional retinal detachment then occurred between 7 and 11 weeks, due to contractile fibrovascular ingrowth from the wound along the vitreous scaffold to the vitreous base, and from preretinal membranes in the peripheral and equatorial retina. The end result at 4 months was tractional total retinal detachment and fibrous cyclitic, epiretinal, and subretinal membranes. This model also showed the role of vitreous hemorrhage as an important nidus for PVR.
In the same year, Topping et al reported a rabbit model for perforating injuries. They used a jagged instrument to penetrate the globe and then continued through the vitreous to create a posterior exit wound. The wounds were not closed, and all procedures were performed in a nonsterile manner. The wounds self-sealed by 7 days, and fibroblastic proliferation was found at the wounds and along the vitreal tract. Fibrosis also occurred on the retinal surface adjacent to the wounds.
These studies together showed that the violated vitreous was acting as a scaffold for directed fibroblastic proliferation, and suggested that vitrectomy to remove the hemorrhage and fibrosis should be performed before the proliferative phases.
Int Ophthalmol Clin. 2013;53(4):127-137. © 2013 Lippincott Williams & Wilkins