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Kai Januschowski, Siegfried Mariacher, Martina Ebner, sven schnichels, jose hurst, Peter Szurman, Karl Ulrich Bartz-Schmidt, Martin Stephan Spitzer, ; An ex-vivo model for the short term IOP development for vitreous tamponades. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):211.
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© ARVO (1962-2015); The Authors (2016-present)
Intraocular pressure (IOP) development of intravitreal tamponades (e.g. silicone oils) are either directly tested in animal models or in spherical model eye chambers; while model chambers are an artificial system without a functioning trabecular meshwork (TMW) and therefore do not reflect the physiological situation well, animal models such as the rabbit eye differ from the human situation significantly and are cost intensive. It was the goal of this study to introduce a standardized and cost effective physiological experimental ex-vivo model that can monitor IOP development with a functioning trabecular and uveoscleral regulation of the IOP and without the high costs.
Pars plana vitrectomy (ppV) was performed on pig eyes and silicone oils were injected (silicone oil 1000, 2000 and 5000, n=5) BSS served as control. Eyes were perfused with DMEM supplemented with 1.5 mg/mL glucose, 1% (vol/vol) fetal calf serum (FCS) and 100 U/mL penicillin, 0.1 mg/mL streptomycin and 17 g/mL gentamycin at a constant flow rate of 4.5 µL/min while the IOP was continuously monitored for 24h. To study cell death in the trabecular meshwork we used fluorescent in situ terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick-end labelling (TUNEL, n = 5).
The TUNEL assay showed a cell death rate of 4.12 % cell death (SD 2.25) in the BSS group (SD) compared to a 5.74 % (SD 2.27) after 1000, 2000 or 5000 ct silicone oil implantation (Manuwhitney, p= 0,209). In the BSS group initial pressure was 13.23 mmHg (SD 5.91) after 1 h, the pressure increased slightly to 18.46 mmHg (SD 14.31) after 12 h and was 15.51 (SD 11.10) after 24. In the 1000 ct group mean IOP after 1 h was 12.81 mmHg (SD 1.79), it increased to 17.30 (SD 7.48) after 12 hours and to 21.01 (SD 6.60) after 24 h. In the 2000 ct group the initial IOP was 10.00 mmHg (SD 3.10) after 1 h, 17.30 (SD 7.50) after 12 h and 19.48 mmHg (SD 11.11) after 24 h. In the 5000 ct group IOP started at 11.83 mmHg (SD 1.62) and increase to 22.14 mmHg (SD 7.46) after 12 h. The IOP remained increased at 22.33 mmHg (SD 5.99) after 24 h.
The trabecular meshwork showed an excellent viability thus indicating a good functionality. IOP development could be monitored for 24 h and is comparable to the literature indicating that the porcine model can be used as an excellent preclinical IOP assessment tool.
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