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Conventional Scanning Electron Microscopy Analysis Of Cornea Surface Damage Induced By Ultrasound

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Ultrasound is an important medical modality because it can provide numerous therapeuticeffects, ranging from increasing drug delivery to a target organ, stimulating an organ to release hormones, and finally for diagnostic imaging. Every year, a great number of patients suffer from various corneal disorders, for example infections, keratoconus, and genetic disorders of the cornea. On one hand, ultrasound exhibits promise in treating these conditions, on the other hand, ultrasound may induce undesired biological effects in the cornea and in other neighboring ocular tissues. Hence, the aim of this study is to investigate and quantify lesions in the form of pits to the corneal cell membrane, using SEM, after applying ultrasound of varying intensities and frequencies. In this study, dissected adult rabbit corneas, from New Zealand white rabbits obtained from a commercial supplier (Pel-Freez Biologicals, Rodgers, AR), were placed inside a diffusion cell in between the donor and receiver compartment, both filled with saline solution. Each set of corneas was subjected to ultrasound for a period of 5 minutes. The sham group did not receive any ultrasound. The range of frequencies utilized were 400, 600, and 1 MHz. The intensities employed varied from 0.5, 0.8, to 1 W/cm^2 . Conventional scanning electron microscopy was then employed to discern and visualize corneal damage. The microscope utilized was an FEI Teneo SEM, manufactured by Thermo Fisher. This microscope has numerous detectors, such as a segmented backscatter detector, an Everhart detector, and three-in-lens secondary electron detectors. In this investigation, the backscatter electron detector was utilized. Once the cornea images were obtained, the total area of the lesions, including corneal membrane damage, as a percentage of the total cell surface area was calculated. Additionally, various mathematical tools, such as integral equations, proportionality calculations, as well as curve fitting were employed to investigate the relationship between the frequency and intensity on the total lesion area. Lastly, differential equations and ML/AI models were presented to describe in detail the mechanism of the ultrasound waves passing through the corneal tissue to obtain further insights on the effect of ultrasound on the corneal epithelium.

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