| ObjectiveWe studied the removal of huge non-magnetic objects by cryotherapy pens of different diameter and foreign body forcep in vitro. Compared with the effects and analysed the applicable scopes using cryotherapy pen to remove the non-magnetic objects. After that, we further explored the factors affecting the frozen capacity. In the rabbit experiments, the retinal function was evaluated following different degrees of intraocular cryosurgery by F-ERG technique. Then, the tissue damage and recovery were observed in lth and3th after surgery. We approached the feasibility of removal intraocular foreign body by cryotherapy pens.Methods1. We selected huge non-magnetic objects of different material and quality. Then, putted them in a small beaker containing BBS solution and on0.32%agar gel surface. Attempted to remove the objects respectively by foreign body forcep,18-gauge cryotherapy pen or20-gauge cryotherapy pen. Evaluated the effects of removal and analysed the applicable scopes using cryotherapy pens to remove non-magnetic objects.2. Irregular toughened glass pieces were placed in a small beaker containing BBS solution and20-gauge cryotherapy pen was attempted to remove the glass pieces under irrigating. In these experiments, we introduced the principle of single variable, including different quality of glass, different diameter of infusion needle, different high of infusion bottle, different angle or distance between infusion needle and glass. Aimed to explore the factors affecting the frozen capacity of cryotherapy pen.3.27adult New Zealand rabbits weighted1.5-2.0kg were randomly divided into3groups:A, B, C. Each group had9rabbits. All rabbits were performed intraocular cryosurgery. Group A and C were treated with cryosurgery of5seconds,10seconds respectively in vitreous chamber. Group B were treated with cryosurgery of5seconds on the retinal surface. The rabbits of each group were examined by flash electroretinogram before operation and on the1th,2th and3th weeks after surgery, respectively. The light microscopy was performed on the lth,3th weeks after surgery. And transmission electron microscope was performed on the3th week after surgery. We evaluated the impacts of intraocular cryosurgery on the two aspects of visual function and tectology aspects.Results1. A obvious compression was observed using foreign body forcep and only one object was removed successfully by foreign body forcep. However, the objects except copper were removed by20-gauge cryotherapy pen, and the most efficient removal was by18-gauge cryotherapy pen, but the agar gel was damaged during the thawing process.2. Data was analysed by SPSS17.0software, chi-square test of independent sample was used. There was no significant difference in frozen ability among different quality of glass(P＞0.05), different diameter of infusion needle(P＞0.05), different high of infusion bottle (P＞0.05). There was statistical difference in frozen ability among different angle(0°,45°,145°) and different distance (5mm,10mm,15mm,20mm) between infusion needle and glass.3. The F-ERG data was analysed by two-way analysis of variance. There were statistical differences among all groups in implicit times of b-wave and amplitudes of b-wave and OPs (P＜0.05).There were no significant differences among all groups in implicit times and amplitude of a-wave (P＞0.05). Compared with the data of preoperation and2th week,3th week after operation, there were significant differences in the lth week after operation, including implicit times of a-and b-wave and amplitudes of a-, b-wave and OPs among all groups (P＜0.05)4. Histological examination of three groups:group B showed large amounts of exudation, retinal ganglion cell swelling and photoreceptor layer degeneration. The lesions of group B were included the full-thickness retina. Group A showed minimal damage. There were scattered degenerative substances on the surface of retina. In group C, we observed that exudation and degeneration of the blood cells in the vitreous chamber, and degenerative substances on the surface of retina. In the3th week after surgery, all groups had different degrees of recovery, and in group A, the retina was seemed to be normal.5. Transmission electron microscope of three groups were performed in the3th week after cryosurgery. Group A showed the minimal damages, which were mainly within the inner plexiform layer of retina. Group B showed the maximal damages, which were including the full-thickness retina. The injuries of group C were mainly within the outer plexiform layer of retina.Conclusions1. It was applicable to remove the foreign body of non-magnetic and non-metallic using cryotherapy pens. The frozen capacity of20-gauge cryotherapy pen was not affected by quality of glass, diameter of infusion needle and high of infusion bottle. But it was correlated to the angle and distance between infusion needle and glass.2. The retina function was less affected by the intraocular cryosurgery of single, small-scale and short-time. It was applicable to remove the huge intraocular foreign body by20-gaug cryotherapy pen.3. The innovation of this study lied in the fact that we first proposed the method of removing intraocular foreign body by cryotherapy pen. The method was more simplicity, rapidity and practicality. |
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