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BackgroundSeveral cornea collagen crosslinking methods have been used to treat keratoconus.However,the safety of these methods is dissatisfactory.Glyceraldehyde is a very potent and highly reactive crosslinking agent,with little toxicity,but its effect on corneal biomechanical property is poorly clear.ObjectiveThe aim of this study was to evaluate the biomechanical effects of glyceraldehyde collagen crosslinking on rats cornea.Methods Fifteen clean SD rats were randomly divided into 0.005 mol/L glyceraldhyde group,0.050 mol/L glyceraldhyde group and blank control group.Glyceraldhyde drops was topically administered in the right ryes 2 times per day for consecutive 7 days in the 0.005 mol/L and 0.050 mol/L glyceraldhyde groups,and no any eye drops was used in the blank control group.Seven days later,the rats were sacrificed.Transparency of corneal buttons in these different groups was evaluated.The central corneal strips of 2 mm×6 mm with 2 mm scleral tiasue were obtained for the biomeehanical stress-strain measurement,including ultimate stress ( MPa),ultimate strain (％) and 6％ elastic modulus (MPa).Corneal collagen fibril density was assessed by histological examination under a light microscopy.The use of the animals followed the Regulations for the Administration of Affair Concerning Experimental Animals by State Science and Technology Commission.ResultsThe words could be clearly displayed transcorneally in all the three groups.When strain was 6％,the stress was (0.463±0.065 ) MPa in 0.005 mol/L glyceraldehyde group,(0.846±0.240) MPa in 0.050 mol/L glyceraldehyde group,both showing a significant increase in comparison with (0.195±0.103 ) MPa of the blank control group (P=0.029,0.000 ).Following the crosslinking treatment,the ultimate stress was significant elevated in 0.050 mol/L glyceraldehydes group compared with the blank control group ( ( 10.759 ± 3.337 ) MPa vs.(5.295± 1.313 ) MPa,P =0.007 ),but no significant change between the 0.005 mol/L glyceraldehydes group and the blank control group ( ( 6.043 ±2.084) M Pa vs.(5.295 ± 1.313 ) MPa,P =0.660 ).Corneal ultimate strain was lower in the 0.005 mol/L glyceraldehyde group and 0.050 mol/L glyceraldehyde group than the blank control group (36.57％ ±3.09％ vs.43.87％ ± 1.89％,P =0.009;28.53％ ±1.89％ vs.43.87％ ± 1.89％,P =0.000).However,significantly increased 6％ elastic modulus were seen in the 0.005 mol/L glyceraldehyde group and 0.050 moL/L glyceraldehyde group compared with the blank control group ( ( 7.718 ± 1.076 ) MPa,( 14.102 ± 4.011 ) MPa vs.( 3.252 ± 1.717 ) M Pa),with statistically significant differences ( P =0.029,0.000).Histological examination showed a increase of collagen fiber density in the 0.050 mol/L glyceraldehyde group.Conclusions Corneal collagen crosslinking induced by glyceraldehyde strengthens biomechanical intensity and increases the density of corneal collagen fiber.But the safety of glyceraldehyde crosslinking for keratoconus needs further study.
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To describe a modified simple iris suture for pupillary dilation technique during vitrectomy in cases with a miotic pupil.Four translimbal incisions were created with a sharp straight blade at 1:30,10:30,4:30,and 7:30 o'clock,respectively.The straight needle of 10-0 polypropylene suture and a Sinskey IOL hook was used to displace the pupillary margin toward the limbus.In 3 cases,four sutures caused a 6-mm to 9-mm square-shaped pupil,and the pupil was allowed to return to a smaller size at the end of the operation.It is simple and may reduce postoperative complications.