The purpose of this study was to establish a standardized in vitro phacoemulsification damage model for future investigations of the effects of phacoemulsification, surgical devices, protective ophthalmic viscoelastic devices (OVDs), irrigation solutions and other aspects related to cataract phacoemulsification surgery on the corneal endothelium using porcine eyes.
Thirty‐four porcine eyes were randomly assigned to three groups (phacoemulsification (n = 13), irrigation (n = 9), control (n = 12)). A total of 5 min of ultrasound energy with intermittent irrigation/aspiration was applied in the eyes of the phacoemulsification group. The eyes of the irrigation group received the identical treatment, but without the application of ultrasound energy. The control group was left untreated. All eyes were then prepared to split corneal buttons followed by 15 days of cultivation. Endothelial cell density (ECD) was assessed blinded on day 15.
Endothelial cell density declined significantly more until day 15 in the phacoemulsification group (2567 ± 317/267 cells/mm² (median ± 25%/75%‐quartiles), −32.5 ± 7.0/6.4%) compared to the irrigation (3450 ± 350/383 cells/mm², −11.8 ± 5.3/2.6%; p < 0.001) and the control group (3650 ± 288/258 cells/mm², −10.2 ± 3.2/4.6%; p < 0.001).
The phacoemulsification damage model presented in this study is sensitive to phacoemulsification energy and may reliably be used to investigate various factors involved in phacoemulsification with regard to their influence on corneal endothelial cells. This method is able to replace animal experiments or in vitro cell culture experiments that often do not translate well to the in vivo situation in humans.
Human corneas usually are not available for research, as they are used for transplantation only. At the same time, scientific studies on cultured human endothelial cells can produce misleading results due to inevitable dedifferentiation. Therefore, an organ-culture model of porcine corneas-displaying endothelial cell death rates comparable to those of cultured human corneas-would be very desirable. Fresh pig eyes were prepared under sterile conditions to obtain corneoscleral buttons, corneal buttons and so called "split corneal buttons" (new preparation method) and cultivated for 15 days. Morphology of the endothelial cell layer was observed by light microscopy on day 1, 8 and 15. On day 15 staining with trypan blue and alizarin red S was performed. Photographs were evaluated in a randomized, blinded manner. Here, the morphology of the corneal endothelium and the number of endothelial cells per mm were analyzed. After 15 days of cultivation the endothelial cell layer was maintained only in corneal buttons and split corneal buttons. Alizarin red S stained areas and the existence of polymorphisms like rosette figures and reformation figures were significantly less frequent in split corneal buttons than in corneal buttons. Loss of endothelial cells was significantly greater in corneal buttons [575 ± 25/250 cells/mm (median ± 25%/75%-quantile); 14.8%] than in split corneal buttons [417 ± 138/179 cells/mm (median ± 25%/75%-quantile); 10.2%]. The new preparation method of split corneal buttons allows the cultivation of porcine corneas for 2 weeks with cell death rates comparable to those of the corresponding human tissue in cornea banks without the need to add de-swelling additives to the media. This is therefore a simple and highly reliable method model to be applied in intervention studies on corneal endothelial cells in their natural compound.
Silicone oil endotamponades need to be injected and removed in a reasonable time and under moderate pressure conditions. However, due to ever-decreasing sizes of incisions and trocars, injection and removal of highly viscous silicone oils is very time-consuming. To address resulting problems like longer treatment times or hypotony, thixotropic silicone oils were developed. These oils are characterized by a diminished viscosity under constant mechanical stress; whilst there is pressure or vacuum acting on it, the oils will become more fluid and, therefore, much easier to be applied. Once the force is being removed from the oil, it will automatically return to its initial viscosity after a short time.
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