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N. Lassota, J. F. Kiilgaard, J. U. Prause, E. Scherfig, M. la Cour; The Development of CNV After Surgical Induction in an Animal Model. Invest. Ophthalmol. Vis. Sci. 2007;48(13):3427.
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To study the time course of surgically induced CNV in a porcine model applying fluorecscense angiography and immunohistology.
22 porcine eyes underwent vitrectomy, a retinal bleb was raised and the detached retina perforated using endodiathermy. Bruch's membrane was perforated with a retinal perforator at a site where the overlying neuroretina was normal. Eyes were enucleated at different time intervals after the perforation: 30 minutes, 3, 7, 14, 28 and 42 days. Immediately prior to enucleation, fundus photographs and fluorescein angiograms were obtained. Sections of paraffin embedded eyes were immunohistochemically stained and examined by light microscopy.
In fundus photographs the CNV membranes appeared yellowish sometimes surrounded by a hypopigmented halo. On fluorescein angiography 82 % of membranes exhibited leakage while the remaining showed persistent staining. The propensity to leak diminished with time and only 1 / 3 of the oldest membranes leaked. In eyes enucleated immediately after surgery neuroretinas overlying the induced lesions were intact without apparent atrophy of cells. At day three a cluster of cells forming a membrane like structure in the subretinal space was identified. Macrophages and myofibroblasts constituted the majority of these cells. At day seven the outer surface of the membrane was covered by RPE cells and blood vessels were identified inside the membrane. The neuroretinas had suffered damage in the form of outer segment loss and a thin glial plaque had formed between the neuroretina and the CNV membrane. In the time period 14 to 42 days the CNV membrane became completely enveloped by RPE cells, which covered all surfaces except for areas where glial plaques had formed. The degree of membrane vascularization increased with time and was at its maximum after 42 days. Intact outer segments were identified over the oldest membranes.
The formation of surgical CNV membranes followed the normal reparatory pathway and the degree of vascularization of CNV membranes continued to increase during the 42 days. However, propensity to leak diminished with time. We believe that this was due to the fact that RPE cells completely enveloped older membrane and thus prevented leakage from the newly formed vessels. Photoreceptor outer segments, which had atrophied after seven days, were able to regenerate over CNV membranes and could be identified again after 42 days.
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