ABSTRACT
Objective To evaluate the effect of two polymer membranes, polyhydroxyalkanoates(PHA)and polylactic acid(PLA)during glaucoma filtration surgery(GFS),and to evaluate the morphology of membranous PHA after interlamellar implantation. Methods Twenty-eight New Zealand white rabbits were chosen and twenty-four of them were randomly divided into 6 groups(n=4):the PHA-low group,PHA-high group,PLA-low group,PLA-high group,positive control group(MMC group)and blank control group. The rabbits in each group received GFS. The corresponding polymer membranes were implanted under the scleral flap,while the MMC group was treated with 0.2 mg/mL mitomycin C(MMC) for 3 minutes,and the blank control group was treated without extra drugs. The intraocular pressure(IOP)was examined at 0 d,1 d, 3 d, 7 d, 14 d, 28 d and 84 d after GFS. The corneal layers of four rabbits were implanted with PHA membranes and the corneal morphological changes were observed after 84 d. Results The IOP of the PHA-low and PLA-high groups was lower than that of the blank control group at 84 d after GFS(P < 0.05),and was similar with that of the MMC group(P> 0.05). Morphological studies showed that there were no collagenous fibers filling in the duct, and the collagenous fibers around the membranes were generally arranged in parallel. There were no obvious changes in the peripheral collagen structure after implantation of PHA membranes between the corneal layers. Conclusions Application of PHA and PLA membranes during GFS in rabbits may maintain the level of IOP,and the effect is similar with MMC. The mechanism may be achieved through the mechanical blocking of fibrous tissue.
ABSTRACT
The authors investigated the toxicity of two antimetabolites. 5-fluorouracil(5-FU) and mitomycin-C(MMC) on the rabbit cornea and sclera following glaucoma filtration surgery(GFS). Forty rabbits were divided into four groups; the first control group(I) was the balanced salt solution soaked group(BSS) during GFS, the second(II) was the 5-FU subconjunctival injected group(5-FU SC) after GFS, the third(III) was the 5-FU soaked group(5-FU) during GFS, and the fourth(IV) was the MMC soaked group(MMC) during GFS. At the fifth day after GFS, scanning electron microscopic findings showed that corneal epithelial cells were most seriously damaged in 5-FU SC group, slightly damaged in 5-FU group, and no change in MMC and BSS group. At six months after GFS, transmission electron microscopic observation on sclera revealed the most profound degenerative changes in 5-FU group, and followed by an order of MMC, 5-FU SC, and BSS group. These results suggest that the dosage and application method of antimetabolites should be selected with great caution to prevent ocular toxicity.
Subject(s)
Rabbits , Antimetabolites , Cornea , Epithelial Cells , Filtering Surgery , Filtration , Fluorouracil , Glaucoma , Mitomycin , ScleraABSTRACT
The most common cause of the postoperative failure of glaucoma filtration surgery(GFS) is scarring secondary to fibroblast proliferation and fibrosis at the interface of the episclera and conjunctive. To inhibit this process, mitomycin C(MMC) has been studied experimentally, both in vivo and in vitro. In evaluating the toxicity of MMC, we observed the inhibition of fibroblast proliferation and of fibrosis by light microscope, and the ultrastructual changes of the sclera by transmission electron microscope following the soaking of MMC during GFS in rabbit eyes. The sixty rabbits which comprised this study were divided into four groups; the first control group(I) was soaked with the BSS during GFS, the second(II), the third(III), and the fourth(IV) group were soaked with the 0.2 mg/ml, 0.5 mg/ml, and 0.5 mg/ml MMC soaked groups, respectively, during GFS as experimental groups. On histologic examination, the degree of proliferation of fibroblasts with fibrosis and infiltration of lymphocytes in MMC soaked groups was less than those of BSS soaked group at 2 weeks and 2 months after GFS. At six months after GFS, there was ultrastructural evidence of degenerative changes of scleral fibroblasts such as clumping of nuclear chromatin, wrinkling of nuclear membrane, and cystic dilatation of rough endoplasmic reticulum in MMC soaked groups. Higher concentration of MMC caused more degenerative changes in cellular structures. These results surggested that the scar formation after GFS could be significantly suppressed by a single application of MMC during surgery, and MMC could be0 used effectively in cases of poor prognosis of GFS. Further experiments need to be conducted to determine the optimal concentration, exposure time, and application method of MMC.