A light and electron microscopic study of the healing of pars plana incisions in the rhesus monkey

Abstract

Pars plana incisions were made in 11 rhesus monkey eyes. Six animals had injections of 0.1 ml of blood into the vitreous cavity with a 25-gauge needle and five animals had vitrectomy through a 4-mm incision with a multifunction vitrectomy probe. Six to 13 years later the scars in the pars plana were found to consist of fibrous tissue and blood vessels which extended from the episclera into the vitreous. The intravitreous scar was shaped by the incarceration of vitreous strands in the internal aspect of the wounds. There were quantitative, but no qualitative differences between the two types of incision. The ultrastructural features were those of mature scar tissue: fibroblasts, adult collagen, uveal melanocytes, macrophages, myelinated and non-myelinated nerves, and capillaries with non-fenestrated endothelium. There were associated proliferative ciliary epithelial changes, but no evidence of ciliary epithelial metaplasia.

An endoscopic overview of the anterior vitreous base in retinal detachment and anterior proliferative vitreoretinopathy

“…; Koch et al. , ). And as early as the beginning of the 1990s, anterior PVR was found to be significantly more frequent in eyes with previous vitrectomy than in eyes without prior surgery (Lewis & Aaberg ; Lewis et al.…”

“…), and ciliary epithelial changes at the pars plana incisions suggested the formation of new vitreous collagen (Koch et al. ). Hyalocytes have been suggested to stimulate cell migration, proliferation and gel contraction and to play a central role in macular pucker pathogenesis (Kohno et al.…”

“…The potential development of anterior PVR after incomplete vitrectomy has been recognized as early as in the 1970s (Buettner & Machemer 1977;P€ ulhorn et al 1977); additional human and animal studies followed in the 1980s and early 1990s (Ho et al 1984;Lewis et al 1987;Kreiger 1991Kreiger , 1993Elner et al 1988;Koch et al 1994Koch et al , 1995. And as early as the beginning of the 1990s, anterior PVR was found to be significantly more frequent in eyes with previous vitrectomy than in eyes without prior surgery .…”

“…It has long been shown that uveal cells and blood components can be displaced into the vitreous cavity (Kreiger 1991). Morphological ciliary stress has been found to be induced at the sclerotomy (Inoue et al 2011), and ciliary epithelial changes at the pars plana incisions suggested the formation of new vitreous collagen (Koch et al 1994). Hyalocytes have been suggested to stimulate cell migration, proliferation and gel contraction and to play a central role in macular pucker pathogenesis (Kohno et al 2009).…”

Development and Ex-vivo Evaluation of a Novel Device to Facilitate and Standardize Intravitreal Injections in Rabbits

“…The optimal location of the needle-penetration-point when injecting into the vitreous is the pars plana which is located between the retina and ciliary body [6][7][8]. This injection location ensures sensitive tissues such as the retina and choroid are avoided [9]. In the rabbit, the pars plana measures only approximately 1 mm and the only external feature that can be used to estimate its location is the distance from the limbus [10].…”