Study On Penetrating Keratoplasty Experiment In Dogs

In order to explore the surgical techniques of keratoplasty performed in pets and to find out therelevant complications and solutions of the surgery, a total of 11 dogs, including Shih Tzu(6),Pekingese (3) and small type of mongrels (2), with ages from 6 to 12 months and weights from4.0 to 6.5Kg were used for experimental penetrating keratoplasty. Following the surgery, therecipient dogs were closely monitored everyday for the general and ocular inflammatorysymptoms and the samples of peripheral blood were obtained every five days during initial 30days and every ten days afterwards to determine serum TNF-α, IL-2 andβ-EP levels byradioimmuneoassay. At the end of postoperative observation for two months or longer onthesuccessful cases or when the dogs were terminated because of suture loosing, anterior chambercollapse and anterior synechia of iris, whole corneas were removed from the operated eyes, fixedin 10% formalin, and sectioned and stained with hematoxylin and eosin for video biomicroscopicexamination.1. Experimental penetrating keratoplasty in dogs: After two months or longer ofpostoperative follow-up, the whole or central part of cornea grafts remained transparent in 5recipient dogs and the other 5 dogs were euthanatized owing to postoperative suture loosing,partial erosion of the graft edge or anterior chamber leak and extensive anterior synechiae of iris.The results indicate that firm and persistent head restraint and general anaesthesia wereparticularly important for keratoplasty in dogs, in addition to local anaesthesia on the eyesoperated. Compound anaesthesia with propofol and ketamine by intravenous drip was lasting andsafe. Under such anaesthesia, the dogs recovered rapidly once the drugs were withdrawn. Severalinteroperative procedures affected greatly the clearness of cornea and success rate of keratoplasty,one of which was satisfactory pupil contracion and lower ocular pressure acquired preoperativelywhen the experimental dogs were administered intramuscularly with 0.05mL of Sumianxin perKg body weight. In addition, the graft ought to be sutured evenly in place and the anterior chamber reconstructed reliably under anaesthesia maintained by intravenous propofol andketamine drip.2. The dynamic change of serous TNF-αconcentration after penetrating keratoplasty indogs: Following the surgery, the serum TNF-αlevels increased by varying degrees in all of therecipient dogs compared with those preoperatively, and the extent of average increase was verysignificant on the tenth postoperative day(P＜0.01) and significant on the fifteenth postoperativeday(P＜0.05). Thirteen days later, the serum TNF-αlevels gradually returned to those ofpreoperative dogs. These findings suggest that subacute immune rejection occurred seldom inhomologous penetrating keratoplasty in the dog with normal cornea. If the rejection did occur, itwas mild.3. The dynamic change of serous IL-2 concentration after penetrating keratoplasty in dogs:Following the surgery the serous IL-2 levels increased by varying degrees in all of the recipientdogs compared with those preoperatively, and the extent of the increase was correlated with theextent of ocular irritation and inflammation. These findings suggest that the serous IL-2 levelmight be an important indicator of the extent of ocular irritation and inflammation followingcorneal transplantation.4. The dynamic change of serousβ-EP concentration after penetrating keratoplasty indogs: Following the surgery the recipient's dog showed marked stress response to corneal wound,pain and suture-knot irritation. The serousβ-EP levels increased by varying degrees in all of therecipient dogs compared with those preoperatively five days after the surgery and afterwards theserousβ-EP levels of the recipients fluctuated irregularly. These findings suggest that proficientkeratoplasty skills, use of high quality monofilament nylon suture, embedment of thesimple-interrupted suture knots, and early application of appropriate analgesic agent should behelpful to prevent the recipient dogs from self-mutilation by pawing and rubbing the operatedeyes and to improve the success rate of penetrating keratoplasty.5. The histopathologic observations of corneas after penetrating keratoplasty in dogs: Thestructure of wholly transparent graft was the same as that of host cornea apart from the upperdonor-host junction where there was minimal irregularity of the corneal lamellae. However, thecorneal lamellae at the lower donor-host junction were neat. The graft with its central part beingtransparent only showed poor coaptation with recipient, in which the graft shifted inward and had marked wrinkles and folds in Descemet's membrane. On the back of Descemet's membranethere was hyperplastic stromal fibers that thickened the graft and partially adhered to iris. Theseresults indicate that the excellent suture skills could ensure retaining the normal corneal structureand transparency, yet poor suture could cause apparent alteration of the corneal structure, leadingto unclear or cloudy graft corneas. It is suggested that use of operative microscope at highmagnification and improvement of suture accuracy could contribute to the maintenance ofcorneal transparency.6. The Effect of DLA-DRB1 Homology on penetrating keratoplasty in dogs: The sequencehomology of the DLA-DRB1 gene was above 95% between dogs 1 and 10 and between dogs 5and 11, and below 90% among donor and recipient dogs that were matched artificially andrandomly. Comparison with the outcome of the penetrating keratoplasty performed suggestedthat the same breed matching is preferred when a donor dog is to be selected among aconsanguinity-unrelated colony for canine penetrating keratoplasty. If the DLA typing or theDRB1 gene sequencing could be performed on the donors and recipients and the DLA-DRB1homology is taken into account when selecting the donor dogs, the extent of postoperativeinflammatory reaction in dogs with penetrating keratoplasty could be decreased.