| AIM: Microwave therapy technology has advantages for its operating convenience, strong controllability, curative accurate effect, few side effect and etc. Microwave, which is the electromagnetic wave, is a kind of ultra short wave. Microwave treatment mechanism is completely different from the laser and high frequency electricity, because it is not to accumulate the high energy in a minimum tissue's area to cause the local tissue getting hotter, but to cause rapidly electric field change and result in the polar molecule in tissue rotary motion oneself to give off heat. Therefore the microwave may have a stronger thermal effect on the tissue with more water. In addition, the local high temperature also may increase the immunity function of organism and may promote the activation of immunity factors. And there is different water content in each tissue of eyeball. These make us have a tentative plan to apply the microwave therapy technology in the ophthalmological treatment. According to literature reports, microwave has been used in treating the melanoma of choroid, retinal glioblastoma, the eyelid and orbital melanoma, pterygium, margo palpebrae, the conjunctiva neoplasm and etc. But the research of applying microwave direct on the cornea has been rarely reported till now. This experiment aims at this topic to take preliminary study on applying microwave on the cornea. The first stage, we have observed and analyzed the effect of different power of microwave with different length of duration time on living rabbit's cornea and eyeball tissue, and furthermore to preliminarily identify the viable range of microwave power and duration. The second stage, we have observed whether microwave can change rabbit's cornea refraction condition as well as it has what kind of influence to each tissue of eyeball after using microwave antenna directly on the living rabbit's cornea. And we preliminarily discussed the feasibility of applying the microwave technology to improve ametropia. METHODS: The first stage: 25 healthy New Zealand rabbits were chosen and randomly divided into 4 groups of different disposal time from immediately after surgery to 1 month later. 6 rabbits (12 eyes) in each group received 2450MHz microwave frequency, 5 to 20W microwave power and the duration of 3 to 7s. The remaining one rabbit(2 eyes) was chosen as a blank control group. We used 2mm-diameter-antenna to provide the microwave output. Different levels of power were applied directly into the peripheral cornea 2mm from corneal limbus through the antenna's tip contact and press lightly at circular symmetrically 6~8 points. Rabbits'eyeball was removed at 1-day (IA group), 3-day (IB group), 7-day (IC group) and 1-month (ID group) after surgery to observe the pathomorphological changes. Cornea, anterior chamber and lens were observed through slit-lamp microscope, the ocular fundus was observed with ophthalmoscope everyday at the same time. In the second stage, 14 healthy New Zealand rabbits were chosen and randomly divided into 7 groups of different disposal time from 1 day after surgery to 6 month after surgery. 7 rabbits (14 eyes) in each group received 2450MHz microwave frequency, 5W microwave power and the duration≤5s, or 10W microwave power and the duration≤3s, and we used 2mm-diameter-antenna to provide the microwave output. Different levels of power were applied directly into the peripheral cornea 2mm from corneal limbus through the antenna's tip contact and press lightly at circular symmetrically 6~8 points. Rabbits'eyeball was removed at 1-day (IIA group), 3-day (IIB group), 7-day (IIC group), 14-day (IID group), 1-month (IIE group), 3-month (IIF group) and 6-month (IIG group) after surgery to observe the changes of pathomorphology. Cornea, anterior chamber and lens were observed through slit-lamp microscope, corneal curvature radius was measured by computer optometry uni, and the morphological changes of cornea were observed through pathological section and transmission electron microscope.RESULTS:First stage: Before the surgery, rabbits'cornea, aqueous humor and lens were transparent, in normal places and shapes. After the surgery, a semitransparent white cylinder footprint could be observed on the rabbits'cornea. The cylinder footprints deepened with the increase of microwave output power and durational time.Checking the rabbits'ocular fundus after the surgery didn't find abnormal changes. After surgery, by studying the pathology slice, we could get a clear image of the loss of corneal epithelium and cylinder injury area with different depth in peripheral cornea. Most endothelial cell layer had not been injured. We could see corneal edema around the injury area, when we observed some pathology slice. Abnormal morphology was not seen in the other eyeball tissues.Second stage: Before the surgery, rabbits'cornea, aqueous humor and lens were transparent , which were in normal places and shapes. After the surgery, a semitransparent white cylinder footprint could be observed with slit-lamp microscope, which was 2/3 corneal thickness.After the surgery, corneal curvature radius had been changed with certain regularity. After surgery, by studying the pathology slice, we could get a clear image of the gentle loss of corneal epithelium and cylinder injury area with different depth in peripheral cornea. The entire endothelial cell layer had not been injured. We could see corneal light edema around the injury area. Abnormal morphology was not seen in the other eyeball tissues.Being observed under transmission electron microscope after the surgery, the swollen corneal cell could be seen. And collagenous fibers were irregular. The morphous of keratocyte tended to be normal after 1-month. The field outside the wound was normal.CONCLUSION:1. By observing the eyeball tissue injury and repair after using microwave directly on rabbits'cornea, the feasibility and security of this surgery under certain microwave power and duration could be verified. It would not cause clear injury and could be directly used on cornea, when microwave power≤5W and the duration≤5s, or microwave power≤10W and the duration≤3s, with 2450MHz microwave frequency.2. After the surgery, the corneal curvature radius could be changed regularly.3. Observing pathology slice and transmission electron microscope proved that if we controlled the microwave power and duration time within the certain range, corneal endothelium would be in the normal conditions.4. Through the experiment, we gradually came to the conclusion that microwave technology for the treatment of cornea was feasible and could be used to improve the refractive state.
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