Experimental Study On The Effect Of Pars Plana Filtration Technique On IOP And Incision-related Morphology Of Rabbits

ObjectiveTo investigate the effect of pars plana filtration technique on ocular region morphology in both normal and glaucoma rabbits, research the mechanism of controlling IOP and its filterable effect on glaucoma model, then identify the security of pars plana incision, thus make it a specification of pars plana filtration surgery, and provide new methods to clinical treatment.Method1.10 normal eyes were divided into two groups, 5 eyes as the treatment group (group 1) received pars plana filtration surgery, others as control group (group 2) received trabeculectomy. To investigate the appearance of the bleb and anterior segment in the condition of overfiltration, observe the intraocular tissue and measure the depth of anterior chamber with Ultrasonography.2.28 eyes as normal-control group, other 28 eyes with high IOP were divided into 4 groups to received nontreatment (group A), trabeculectomy (group B), pars plana filtration surgery (group C), or pars plana filtration surgery combined silica gel pipe implantation (group D) differently. To investigate IOP, the appearance of the bleb, and anterior segment, observe the intraocular tissue and measure the depth of anterior chamber with Ultrasonography. Then study the ocular region histopathology under light microscope.Result1. On normal rabbits: From postoperative 1^st to 3^rd day, group 1 had complication with flat chamber but group 2 had anterior chamber deepened, there's significant difference between two groups (P<0.01) . From 7^th to 15^th day, anterior chamber of group 1 deepened a lot but still shallower than group 2, and there's still difference between them(P <0.05) . In group 2, there's no abnormity after surgery except several eyes had vitreous overflowed from incision at 1^st week.2. Effect on IOP of postoperative glaucoma rabbits : In first 3 weeks after injecting carbomer in group A, the IOP maintained above 30mmHg, then from 4^th to 5^th week it was above 25mmHg, but fell to normal value from 6^th to 7^th week. Three kinds of filtration surgerical techniques could control IOP well in first 4 weeks, but there's no significant difference among them in statistics. In 6^th week, the effect of group D was better than group C when group B had nearly no effect. 3. Effect on the depth of anterior chamber in postoperative glaucoma rabbits : Within 7 weeks after injecting carbomer in group A, the anterior chamber was obviously deeper than normal value. At postoperative 1^st week, group B had complication with flat chamber, and there's difference between group B and C (P<0.05) . From 2^nd to 6^th week, the depth of group B was always smaller than group C and D, but there's no significant difference among them (P>0.05) .4. Effect on the ocular region morphology of postoperative glaucoma rabbits:4.1 Appearance and function of the bleb: All eyes had functional bleb in the first 3 days after operation. From 1^st to 4^th week, the rate of functional bleb in group C and D was higher than group B. At 6^th week, the rate was the same between group C and D, but group B had no functional bleb. No one postoperation was found bleb leak.4.2 Appearance of anterior segment: Within first 2 weeks after injecting carbomer in group A, conjunctive was congested and oedematous, the cornea was obviously expanded with cloudiness, oedemas, and neovascula. From 3 ^rd to 5^th week, the above-mentioned inflammatory reaction had improved and at 7^th week disappeared. The symptoms had improved after surgery in group B, C and D. Otherwise, 1 eye in group B had a little exudation in anterior chamber at 1^st week, then conglutinated at 8^th week.4.3 UBM inspect result: UBM showed eyes in group B had filtered aisles gradually turned narrow from postoperative 1^st to 2^nd week, then only 1 eye had filtered aisle at 4^th week, but none from 6^th to 8^th week. In group C, filtered aisles were smooth with a little vitreous in incision in first two weeks, then turned narrow at 4^th week, and not smoothly enough but still little vitreous in incision from 6^th to 8^th week. In group D, filtered aisles were smooth in first two weeks, but turned narrow at 4^th week, then it found conjunctive kept close to scelra flap and the silica gel pipe at 6^th week, finally it's not smoothly enough at 8^th week. But no eye had vitreous overflowed from 1^st to 8^th week in group D.4.4 B-scan inspect result: The eyeballs in group A were larger with staphyloma and vitreous opacification in first 5 weeks, and 1 eye found vitreous proliferation at 7^th week. Eyes in group B, C and D found no abnormity except 1 eye in group D found vitreous mambrane and choroids edema at 6^th week.5. Light microscope result:5.1 Eyes in blank-control group were normal without infiltration of lymphocyte or inflammatory cells.5.2 Group A: 2 weeks after injected carbomer, cornea was obviously oedemas with many neovascula in epithelium layer, the angle of anterior chamber was jammed, and there were inflammatory cells infiltration intraocular, the cup of optic nerve deepened. At 5^th week, cornea turned thiner, neovascula were atrophtied, a little exudation was in anterior chamber, and the optic nerve oligodendroglias were increased but less capillary vessel around. At 9^th week, cornea was cloudy, neovascula were fadeaway, optic nerve demyelinated and neuraxon disappeared.5.3 Group B: At postoperative 1^st week, eyeballs expanded and the cup of optic nerve deepened.There were numerous inflammatory cells and proliferated fibroblasts infiltration around incision, but filtered aisles were smooth. At 4^th week, the inflammatory reaction improved, filtered aisles blocked with scar formation, and the optic nerve oligodendroglias were increased but less capillary vessel around. At 8^th week, there was limited conglutination in scleral flap gap and incision scared over, 1 eye had a little exudation in anterior chamber, and another eye had intraocular stale hemorrhage and eyeball atrophy.5.4 Group C: At 1^st week, there were numerous inflammatory cells and proliferated fibroblasts infiltration around incision with a little vitreous, suprasclera and ciliarybody were loosen, filtered aisles were smooth. At 4^th week, filtered aisles turned narrow. At 8^th week, conglutination limited in scleral flap gap and incision, then the scar formation made filtered aisles blocked uncompletely. The change of optic nerve were similar to group B.5.5 Group D: At 1^st week, there were more inflammatory cells and proliferated fibroblasts infiltration around silica gel pipe than incision, yet nearly no vitreous in incision. At 4^th week, filtered aisles were still smooth, then little scar formation round incision at 8^th week but filtered aisles opened. Other results was similar to group C.Conclusion1. In the condition of overfiltration in normal eyes, the pars plana filtration technique didn't cause flat chamber, but had anterior chamber deepened instead.2. There was nearly no difference in the effect on controlling IOP between trabeculec-tomy and pars plana filtration technique in a short period of time, but the latter had longer curative effect.3. Compared with trabeculectomy, pars plana filtration technique could make lager incision in order to inhibit the scar formation. And the implantation of silica gel pipe could also delay the scar formation then help to control IOP.4. The implantation of silica gel pipe could help to reduce the happening of vitreous wedge in pars plana incision.5. The security could be identified that the ocular tissues hadn't serious injury with pars plana filtration technique.