Preliminary Study Of High Intensity Intensity Focused In Correcting Presbyopia On Rabbits Cornea

Objective:We use High Intensity Focused Ultrasound (HIFU) to irradiate rabbit cornea in vitro and form in different concentric annular focal region of different diameters.So we can observe the effects of HIFU with different dosages irradiated on rabbit cornea organization and diopter in vitro. We want to assess the efficiency and safety of correcting presbyopia with HIFU and establish the suitable parameters of the HIFU irradiating rabbit cornea in vitro, and then provide an experimental basis data for correcting presbyopia with HIFU.Methods:Establish an animal model of the HIFU irradiating rabbit cornea in vitro.The experiments which use fresh rabbit eyes in vitro,divided into control and experimental group and control group rabbit eyes received no experimental treatment do normal blank control. The experimental groups were irradiated with HIFU in different powers(1w,2w,3w,4w), under the same treatment time(6s) in cornea stroma, formed in different concentric annular focal region of different diameters (8mm,9mm,10mm). After that all groups were observed for the focal region classification under the naked eyes and the annular focal region under the hemotoxylin and eosin (HE), and digimizer software measuring the maximum width and length of the focal region. The normal group and the control group only for power1w, power3w, diameting9mm focal region groups were observed the ultrastructure examination under the transmission electron microscope (TEM) and the refractive changes under the automatic subjective refractometer and the corneal topography.Results:1. Successfully established an animal model of the HIFU irradiating rabbit cornea in vitro.2. Corneal stroma after HIFU irradiation, the colour of the cornea were off-white, clear boundary generally observed under the naked eyes. And there is no corneal epithelial damage.3. After HIFU irradiation, focal region within the corneal stroma oval-shaped, the color deepened, and clear boundary, the board layer fiber of the focal region were marshalling, shrinking in the borderline under the light microscope. The interval between the shrinking fibers of the different experimental groups of3w,4w and2w/8mm group decreases, and the the borderline fiber shrink significantly. Compared with the non-irradiated stromal cells volume, the volume of stromal cell within the focal region is significantly reduced. Meanwhile, with the same focal region loop diameters of the HIFU, the maximum width and length of the focal region got longer when the powers of the HIFU got increased, the difference was statistically significant (p<0.05),while with the same powers of the HIFU, the maximum length of the focal region were shorten when focal region loop diameters got increased,the difference was statistically significant (p<0.05).4. The fiber of the cornea storm were significantly distort and mitochondria and cytoplasm of the cells were dissolved in3w/9mm group and slightly bent in lw/9mm group under the TEM.5. After the HIFU irradiation the corneal curvature radius decreased and the corneal diopter increased in lw/9mm group and3w/8mm group, the difference between before and after HIFU irradiation was statistically significant differences (P<0.05), while the difference between lw/9mm group and3w/9mm group after the HIFU irradiation was was statistically significant differences (P<0.05).The corneal topography test results show that:regardless of the level of HIFU irradiation power, HIFU after irradiation can cause the increase in corneal curvature.Conclusions:1. HIFU can be accurate positioning in the corneal stroma, a clear dividing line between irradiation and non-irradiated, HIFU has no significant effect on normal tissue of the area outside irradiation, show that non-invasive exploration mode correction of presbyopia use of HIFU with less damage, and positioning accuracy. That HIFU applied to rabbit corneas non-invasive correction of presbyopia with great application prospects.2. The size of focal region within the corneal stroma of the different experimental groups of the power1w,2w/9mm group and2w/10mm group is appropriate, and only fiber contraction change, no cell damage, that irradiated corneal correction model of presbyopia is more appropriate. Histological and morphological results, which has a higher security, while this experiment that used HIFU to correct presbyopia provides an experimental foundation and the basis for the following experiments.3. Thermal effects of the HIFU can shrink the collagen fibers of rabbit corneal stroma in vitro, resulting in corneal lordosis effect, decrease rabbit radius of curvature and increase the curvature, and more obvious with the increase in corneal curvature of the irradiation power increases. HIFU is expected to become a new method of correction of presbyopia.