To compare the effects of different intraocular infusion solutions on histology and function of retina.

Human corneal endothelial cells (HCEC), human retinal pigment epithelium (HRPE) cells and rat retinal ganglion cells (RGC) were divided into normal control group, balanced saline solution (BSS) group and compound electrolyte intraocular irrigating solution (CEIIS) group, and the cells were cultured in 10% DMEM/F12 medium, BSS and CEIIS for 12, 24 and 48 hours, respectively, according to grouping.The proliferation absorbance value of cultured cells was measured by cell counting kit-8 (CCK8) method.The expression of apoptosis related proteins in cultured cells was detected by cellular immunofluorescence staining.The cell apoptosis rate and cell cycle were measured by flow cytometry.The mitochondrial damage was detected by lactate dehydrogenase (LDH) and succinate dehydrogenase (SDH) quantitative detection kit.Fifteen New Zealand white rabbits were randomly divided into control group (n=3), BSS group (n=6) and CEIIS group (n=6). The left eyes were taken for vitrectomy and different intraocular perfusion fluids were used during vitrectomy according to grouping.The retinal function of operative eyes was measured by flash electroretinogram (ERG) before operation and 24 hours after operation, and the structural changes of each layer of retina were detected by optical coherence tomography (OCT). The early apoptosis of retinal cells was detected by TUNEL staining.The expressions of cytochrome C and bax protein in retina were detected by immunohistochemical staining.The ultrastructural changes of retina were observed under a transmission electron microscope.The use and care of animals complied with the ARVO statement.This study protocol was approved by an Ethics Committee of Peking University People's Hospital (No.2019PHE059).

The three kinds of cultured cells in BSS and CEIIS groups were damaged in various degrees.With the extension of culture time, proliferated cells were decreased and the number of apoptotic cells was increased.Compared with the BSS group, cultured cells in the CEIIS group were dense and in orderly arrangement with uniform morphology and size.The apoptosis rates of HRPE cells and RGC in the BSS group were (37.157±6.918)% and (29.993±12.330)%, respectively, which were significantly higher than (4.163±1.310)% and (6.337±1.903)% in the CEIIS group (P=0.003, 0.045). There was no significant difference in G0/G1+ S phase ratio of HCEC and HRPE cells among the normal control group, BSS group and CEIIS group (HCEC: F=2.226, P=0.189; HRPE: F=2.634, P=0.151), and the proportion of G2/M division arrest phase of RGC in the BSS group was significantly higher than that in the normal control group and CEIIS group (P=0.047, 0.024). The proliferation absorbance values of HCEC, HRPE cells and RGC in the CEIIS group were significantly higher than those in the BSS group at each culture time point (all at P<0.05). The fluorescence intensity of cytochrome C, bax, caspase-3 and caspase-9 proteins in the BSS group was stronger than that in the normal control group and CEIIS group, and the fluorescence intensity of bcl-2 was weaker than that in the CEIIS group, and the fluorescence intensity of zonula occluden-1 (ZO-1) was weaker than that in the normal control group and CEIIS group.The release level of LDH in the BSS group was significantly higher than that in the CEIIS group at different time points (all at P<0.001). After 48 hours of culture, the release level of SDH in the BSS group was significantly higher than that in the CEIIS group (P<0.05). No retinal histological abnormalities was found through OCT examination of rabbit eyes after vitrectomy in the two groups, but transmission electron microscopy showed that there were different degrees of loose arrangement of retinal photoreceptor cells, a large number of photoreceptor outer membrane discs falling off and vacuolar degeneration in the two groups, especially in the BSS group.TUNEL staining showed that the apoptotic cells were mainly located in the inner nuclear layer and RGC layer.The number of apoptotic retinal cells was (135.2±22.8)/high-power field of vision in the BSS group, which was significantly higher than (81.3±17.7)/high-power field of vision in the CEIIS group (t=4.175, P=0.002). Full field flash ERG showed that the amplitudes of scotopic 3.0 ERG a- and b-wave in the CEIIS group after operation were significantly lower than those before operation, but the differences were not statistically significant (all at P>0.05). The amplitudes of scotopic 3.0 ERG a- and b-wave in the BSS group after operation were significantly lower than those before operation (P=0.026, 0.010).

In vivo and in vitro research results show that compared with BSS, there were few apoptotic cells in retinal tissue after vitrectomy perfused by CEIIS.

Vitrectomy; Infusion solutions; Cell viability; Retinal function; Apoptosis; Oxidative stress