To Estimate the Axial Elastic Modulus of Eye and Posterior Wall Thickness in Healthy Human Eye by Ultrasound Images and their Relation with Age and Gender

Introduction: Based on the invasive studies it has been shown that factors such as age, the progress of eye disorders, lens fibers compression and the biochemical changes of ocular matrix alter the physical characteristics and elastic properties of eye. In this study, a noninvasive method of estimating human eye elasticityis proposed and its relation with age and gender is evaluated using ultrasound images. Materials and Methods: To estimate eye elasticity, an especial loading system was designed and an external stress of 2614 ± 146 Pa which is less than the intraocular pressure of eye was applied to 20 eyes in an in vivo study. The pressure was measured using digital force gauge. The ultrasound images of B-mode were acquired prior to and post applying the stress. For the offline study throughout the loading process, the ultrasound images were saved as multi-frames into the computer by video grabber board. Monitoring, saving and further study of images were provided for the extraction of eye axial length and posterior wall thickness (PWT). The elasticity was estimated by measuring the relative changes of the axial length of eye, the posterior wall thickness and the applied stress. The statistical correlation of elastic modulus was analyzed based on age and gender. Results: The elastic modulus of the eye and the posterior wall thickness was estimated to be 51,777 ± 27304 and 14603 ± 4636 Pa, respectively. The obtained results indicated that there was no significant difference between the elastic parameters of the eye and the posterior wall thickness based on gender in both male and female group. The correlation analysis of the elastic parameter showed that there was significant difference between the eye and the posterior wall thickness based on age with a 95% confidence interval. Discussion and Conclusion: Based on the results obtained in this study the ultrasonic instruments might be used to estimate the hardness of eye lesions as well as eye posterior wall thickness.