The Study On Biomechanical Properties Of Sclera After Posterior Sclera Reinforcement Operation

Progressive myopia is induced by the axial elongation of the eyeball. At present as an effective method to treat progressive myopia, the posterior sclera reinforcement operation (PRS) is designed to strengthen the weakened and thinned sclera by using reinforcement materials, thus to prevent the axial elongation of the eyeball and the deterioration of optical function.In this paper, PSR were performed on normal rabbit eyes. During different period after the operation, the cutting of sclera samples was performed. Using Instron 5544 mechanical machine, the biomechanical properties were measured, including the implanted areas of the operated eyes, the areas near the implanted area, the corresponding areas of the control eyes, the circumferential areas of the operated eyes and the corresponding areas. At the same time, associated with Bethune International Peace Hospital, some samples were chosen to detect the collagen content of the sclera, both in the implanted areas of operated eyes and in the corresponding areas of the control eyes, in order to explore the possible relationships between the collagen changes and the biomechanical characteristics.The main work both in experiments and in theories is: 1. Fifty rabbits were divided randomly into five groups, sclera were obtained from these animals. For each rabbit, only one eye was selected randomly to perform PRS, the other was the control eye. After one month, two months, three months, six months and nine months respectively, the sclera samples including the implanted areas of the operated eyes, the areas near the implanted area, the corresponding areas of the control eyes, the circumferential areas of the operated eyes and the corresponding areas were cutted.2. At the same time, the collagen content in sclera samples was detected by acid hydrolysis technique both in the implanted areas and in the corresponding areas.3. As a simple and effective method, uniaxial tension was chosen. The sclera samples obtained after one month, two months, three months and six months were axial tensed in pretesting, relaxing, creeping and deforming. A series of dates and curves that represent conventional mechanical properties and viscoelastical properties were obtained. At the same time, the problems in axial tension were founded out, so a new experimental method were chosen.4. The experimental method was improved, by using a ball to press the sclera samples, which were obtained nine months after surgery. The pretesting, relaxing and creeping experiments were carried out. In order to compare these two methods, the sclerasamples obtained after nine months also were tested with uniaxial tension.5. Through ball pressing method and uniaxial tension method, sclera relaxing and creeping curves were obtained, the sclera were treated as standard linear viscoelastic bodies, and the viscoelastical coefficients were calculated by least square method.6. For rabbit sclera that in implanted areas and in the corresponding areas of the control eyes, the conventional mechanical properties were analyzed statistically and compared. The sclera viscoelastical properties get by the different testing methods were analyzed statistically and compared. The changes of the collagen content and the biomechanical properties after PSR were analyzed statistically and compared, too. hi this way, some theoretic evidence to popularizing the PSR in human myopic eyes were founded.