A light microscopic and autoradiographic study of non-irradiated and irradiated ocular wounds

Abstract

Focal gamma irradiation was used to limit the intraocular extension of scar tissue which typically occurs after posterior perforating injury to the eye. Standard posterior perforating injuries were created in the right eye of forty-eight rabbits, half of which had the site of perforation focally irradiated using a Cobalt 60 ophthalmic plaque. Non-irradiated wounds healed with profuse formation of highly cellular and vascularised granulation tissue which invaded the vitreous to form contractile vitreo-retinal membranes. In irradiated eyes vitreo-retinal membrane formation was infrequent; the wounds showing only sparse granulation tissue with little or no extension into the vitreous cavity. Autoradiographic studies carried out in a second group of 40 animals showed that the episclera was the main source of the proliferating fibroblasts, and cell counts confirmed that the inflammatory and repair responses in irradiated wounds were both delayed and attenuated.

Radiotherapy of exudative age-related macular degeneration; a clinical and pathologic study

“…Radiotherapy affects the evolution of exudative macular degeneration by endothelial toxicity, resulting in narrowing or occlusion of blood vessels [2,9,13]. Endothelial cells are moderately sensitive to irradiation and vessels may reveal manifestations of radiation injury months to years later [1,2,3,23].…”

“…The mechanism of the effect of ionizing radiation on CNV is not known in detail. Radiotherapy affects the evolution of exudative macular degeneration directly by endothelial toxicity, leading to capillary closure [2], and/or indirectly through its attenuating effects on the inflammatory response, mediated by macrophages and other inflammatory cells [2,9,13].…”

Results of radiotherapy of subfoveal neovascularization with 16 and 20 Gy

“…24,25 The rationale for radiotherapy of ARMD with fairly low doses is to suppress the inflammatory and exudative component of ARMD as well as to inhibit further pathologic endothelial cell proliferation. 17,18,26 All of these features were demonstrated in experimental choroidal neovascularization in rabbit eyes. 27 The degenerative process itself and the persistence of the stimuli that upregulate the growth factors are probably not altered by radiotherapy.…”

“…In vitro and in vivo experiments demonstrated that irradiation inhibits the proliferation of endothelial cells, reduces the neovascular component of healing ocular wounds and may induce vessel obliteration. [17][18][19][20] Low-dose radiation (p25 Gy) has been shown to cause DNA-breaks, decrease cell replication and reduce prostacyclin synthesis and prostacyclin production. [21][22][23] Radiation also increases cell permeability and induces vascular cell apoptosis in vitro.…”

Low-energy Stereotactic Radiotherapy for Treatment of Exudative Age-related Macular Degeneration Adjunctive to Anti-VEGF Therapy

“…[10][11][12] IR in combination with either anti-VEGF or anti-platelet-derived growth factor (PDGF), or both, results in enhanced endothelial apoptosis and reduced endothelial cell migration compared with either agent alone. 13 Besides, IR is able to reduce the macrophage-mediated retinal inflammation and causes a capillary closure, both reducing a local oedema of the retina.…”