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L.I. Ivert, P. Gouras; Comparing Trans–Scleral With Trans–Vitreal RPE Biopsies in Rabbits . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4163.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: To compare the ease of surgery, viability and purity of RPE cells obtained by biopsies using a trans–scleral versus a trans–vitreal approach to the RPE layer in vivo. Methods: The trans–scleral approach is performed under a scleral flap using a surgical incision 2–3 mm behind the limbus. The choroid is dissected away in small pieces with a membrane hook and the pieces examined microscopically to identify the tissue as choroidal. Choroidal bleeding stops rapidly and the RPE and retina become exposed on a convex vitreal bulge. The RPE and accompanying pieces of neural retina can then be removed in patches and examined microscopically to identify RPE cells and the patches cultured. The trans–vitreal method involves forming a scleral port, producing a local vitrectomy, a bleb detachment and then rubbing and sucking up RPE cells off Bruch’s membrane, which are centrifuged and cultured. The retinal region of the biopsy is not as peripheral as that of the scleral method. The incisions are closed and the eyes are examined after the surgical procedures. Cultures are examined weekly for cell survival, purity and proliferation. Results: Choroidal tissue can be identified by the presence of melanocytes and the RPE layer identified by the presence of hexagonal RPE cells and accompanying photoreceptors using compound microscopy from the tissue obtained from surgery. Successful cultures of RPE can be established with a 80–90 % success rate with either method. But the amount of retina that must be denuded to obtain sufficient RPE cells for culturing is larger, at least 10 fold, with the trans–vitreal than the trans–scleral approach and the amount of neural retinal damage consequently greater and more central. The chance of contamination with choroidal cells is greater with the trans–scleral biopsies. Both methods cause no significant additional damage to the eye although there is less inflammation and intraocular pressure reduction with the trans–scleral method. Conclusions: Trans–scleral RPE biopsies are easier, more efficient and less traumatic than trans–vitreal biopsies for obtaining sufficient samples of RPE cells for culturing but the chance of contamination with choroidal cells is greater. Better optics could reduce the latter problem. Trans–scleral biopsies, being more peripheral than the trans–vitreal ones, have the added advantage of being easily amenable to obtaining adult retinal stem cells reported to exist uniquely in the pars plana and pars plicata regions of the eye.
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