| The biomechanical properties of corneal can be enhanced by riboflavin/UVA collagen crosslinking (often referred to’CXL’). After CXL was first introduced in clinical by Wollensak G in 2003, a large number of studies were carried out. The results show that, CXL can enhance the stiffness of corneal and halt the progression of keratoconus.The cornea of keratoconus becomes thinning and projections progressively. The pathological change of pathological myopia sclera is similar to keratoconus. The sclera of pathological myopia, especially the posterior pole sclera, becomes thining, and the biomechanical properties weakening with the deepening of myopia. CXL can strength the stiffness of the sclera and prevent the progression of pathologic myopia and other scleral diseases theoretically.Wollensak administrated riboflavin/UVA collagen crosslinking on rabbit sclera, though the stiffness of sclera was enhanced, there were pathological changes in retinal. Zhang found the optical parameters of riboflavin/UVA scleral collagen crossinking, i. e. under the condition of 0.1% ribof lavin with UVA (365 nm) at energy density 3 mW/cm2, the optical illuminating time is 40 minutes. With such parameter, the sclera enhanced significantly and no retinal damages were found. However, the poor penetration of UVA limits its application in sclera. Besides 365 nm,445 nm is another absorption peak of riboflavin, thus, blue light is also suitable for crosslinking. The penetration of blue light is bigger than UVA, and it is more suitable for scleral collagen crosslinking.Iseli administrated blue light (465 nm) crosslinking in rabbit sclera, found that the stiffness of crosslinked sclera enhanced three times and no retinal damages were found. The wavelength of 440 nm is more close to the absorption peak of riboflavin than 465 nm, and it is more suitable for riboflavin/blue light crosslinking. The first part of our study is to investigate whether blue light (440 nm) is suitable for scleral crosslinking, and the second part of our study is to investigate the optical irradiation time of riboflavin/blue light (440 nm) crosslinking.Part Ⅰ:Effect of riboflavin/blue light (440 nm) UVA crosslinking in rabbit scleraPURPOSE:To investigate the effect of riboflavin/blue light (440 nm) scleral crosslinking and riboflavin/UVA scleral crosslinking, and demonstrate whether blue light (440 nm) is suitable for scleral crosslinking.METHODS:This study involved 36 New Zealand white rabbits. The animals were divided into 3 groups randomly depending on the irradiation parameter. Grope Ⅰ irradiated by 365 nm at energy density 3 mW/cm2 for 40 minutes; grope Ⅱ irradiated by 440 nm at energy density 10 mW/cm2 for 40 minutes; and grope Ⅲ irradiated by 440 nm at energy density 10 mW/cm2 for 10 minutes. Scleral crosslinking only administrated on the upper nasal quadrant of left eye of each rabbit. The right eyes as control grope, without any treatment. One eye in each treated group was used for light microscopy. The other treated eyes and corresponding control eyes were used for biomechanical testing. The biomechanical parameters examined were ultimate stress, Young’s modulus, and the physiological modulus.RESULTS:1、Compared with control grope, the ultimate stress, Young’s modulus, and the physiological modulus of grope Ⅰ、Ⅱ and Ⅲ had significant increase (p<0.05).2、One factor ANOVA of grope Ⅰ、Ⅱ and Ⅲ:ultimate stress:F=0.26, p=0.78; Young’s modulus:F=1.04, p=0.37; the physiological modulus:F=0.76, p=0.48.3、Allirradiated regions showed inflammation reaction. Eyes that irradiated by 365 nm at energy density 3 mW/cm2 for 40 minutes (grope Ⅰ) and eyes irradiated by 440 nm at energy density 10 mW/cm2 for 10 minutes (grope Ⅲ) without exhibiting retinal damage. Eyes that irradiated by 440 nm at energy density 10 mW/cm2 for 40 minutes (grope Ⅱ) exhibited retinal damage.CONCLUSIONS:1、Riboflavin/blue light (440 nm) crosslinking can increase the biomechanical stiffness of rabbit sclera.2、The larger of cumulative energy illuminated, the more obvious effect of collagen crosslinking, and too large cumulative energy can cause retinal damage.3、When blue light (440 nm) energy density is 10 mW/cm2, the safety and efficacy irradiation time of rabbit scleral crosslinking is 10 minutes.Part Ⅱ:The optical irradiation time of riboflavin/blue light (440 nm) crosslinking in rabbit scleraPURPOSE:To compare the effect of riboflavin/blue light (440 nm) crosslinking in rabbit sclera under different irradiation time and find the optical irradiation time of riboflavin/blue light (440 nm) scleral crosslinking.METHODS:This study involved 10 New Zealand white rabbits. Grope Ⅰ included all left eyes of rabbits, which irradiated by 440 nm at energy density 10 mW/cm2 for 5 minutes; and grope Ⅱ included all right eyes of rabbits, which irradiated by 440 nm at energy density 10 mW/cm2 for 20 minutes. Scleral crosslinking only administrated on the upper nasal quadrant. One eye in each group was used for light microscopy. The other eyes were used for biomechanical testing. The biomechanical parameters examined were ultimate stress, Young’s modulus, and the physiological modulus.RESULTS:The date of control grope still use the outcomes of part Ⅰ of our study, ie. The ultimate stress, Young’s modulus and the physiological modulus of control grope is 6.47 ± 1.53 MPa,2.95±1.92 MPa and 4.03 ± 0.50 MPa, respectively.1、Compared with control grope, the ultimate stress, Young’s modulus, and the physiological modulus of grope Ⅰ did not has significant increase (p>0.05).2、Compared with control grope, the ultimate stress, Young’s modulus, and the physiological modulus of grope Ⅱ had significant increase (p<0.05).3、All irradiated regions showed inflammation reaction. Eyes that were irradiated by 440 nm at energy density 10 mW/cm2 for 5 minutes without exhibiting retinal damage; and eyes irradiated by 440 nm at energy density 10 mW/cm2 for 20 minutes exhibited retinal damage.CONCLUSIONS:Combined with the outcomes of part Ⅰ, when energy density is 10 mW/cm2, the optical irradiantion time of 0. 1%riboflavin/blue light (440 nm) rabbit scleral crosslinking is 10 minutes. |
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