Experimental Studies Of Collagen Cross-Linking(CXL)by Sclera Of The Rabbits

ObjectiveThe collagen crosslinking induced by riboflavin and ultraviolet A has been shown significant increase of biomechanical strength and long-term effectiveness of rabbit sclera without side effects in vitro and laboratory animals.However,the previous method need to rotate and hold the globe to expose the target sclera while irradiating which lead to related ocular tissue damage and could not expose the area of the posterior sclera.The aim of this study was to come up with a novel method that is minimally invasive and could effectively irradiate the area of the posterior sclera which names “The method of collagen crosslinking by using minimally invasive riboflavin and ultraviolet A in the sclera”.A series of experiments on the living rabbits were carried out to verify the suitable experimental parameters,the validity and safety of the method.Methods70 clean and healthy New Zealand rabbits whose weight were in the range of 2.0Kg to 2.5Kg were divided into 7 groups randomly and averagely which names respectively that the normal control(group Ⅰ),1 day after crosslinking(groupⅡ),7days after crosslinking(group Ⅲ),15 days after crosslinking(group Ⅳ),1 month after crosslinking(group Ⅴ),2 months after crosslinking(group Ⅵ)and 3 months after crosslinking(group Ⅶ).The experimental parameters were set as follows: set the parameters of the ultraviolet A instrument(wave length: 370 nm,energy density:3m W/cm2,irradiation time: 30 minutes),insert the probe of the light source into the eye to irradiate the area of the posterior sclera,dropped riboflavin of concentration of0.1% into the eye once every 2 minutes for 20 minutes.Execute the rabbit at the time which was defined by the time of its belonging group to gather and store the eyes.In every group,6 rabbits were selected randomly to be used for biomechanical test to analyze the change of the biomechanics characteristics,the residual 4 rabbits were used for TUNEL test and HE test in order to analyze the histopathology change.Results1.The results of the the scleral thickness showed that comparaing the scleral thickness of the 7 groups,there was no statistical difference among the groups and among the eyes,there was no interaction between the eyes and the groups.2.The results of the the biomechanical test contained 6 parts.There was statistical difference among the groups,there was statistical difference among the eyes,there was interaction between the eyes and the groups.Compare the groupⅠwith the residual 6 groups,there was no statistical difference between the left eyes but there was statistical difference between the right eyes.Compare from group Ⅱ to group Ⅶ,there was no statistical difference between the left eyes and between the right eyes.Compare the group Ⅱ to group Ⅵ with the group Ⅶ respectively,there was no statistical difference between the left eyes but there was statistical difference between the right eyes.Compare within the group Ⅰ,there was no statistical difference between the eyes.Compare within the group Ⅱ to group Ⅶ respectively,there was statistical difference between the eyes.3.The results of the microscope examination indicated that the method had no pathological damage to the the tissues of the eyes such as the corneal,the sclera,the iris,the ciliary body and the choroidea.4.The results of the retinal cell apoptosis detection indicated that the value of the retinal cell apoptosis rate of the control group was 11.00% and the average value of the retinal cell apoptosis rates of the remaining 6 groups was 12.13%.Futhermore,there was no statistical difference among the retinal cell apoptosis rates of the 7groups.ConclusionsCollagen crosslinking by using the minimally invasive riboflavin and ultraviolet A in the rabbit sclera can effectively improve the biomechanical property of the sclera but had no obviously pathological damage to the tisssues of the eyes.In addition,the collagen crosslinking effect would decline gradually over time.