Cryosurgical treatment for experimentally induced cataract in dogs 260 ## - PUBLICATION, DISTRIBUTION, ETC. (IMPRINT)
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Date
2000
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Department of Surgery, College of Veterinary and Animal Sciences,Mannuthy
Abstract
This study was conducted with the objective of comparing the efficacy of cryo-coagulation and intra-capsular cryo-extraction of experimentally induced cataract in dogs. Twelve nondescript dogs aged approximately one year were used for the study in two groups, A and B, each consisting of six animals. Two clinical cases of cataract were included under the study as Group C. In all the animals of Group A and B, cataract was experimentally induced by injection of 0.5 ml of a 25% solution of calcium borogluconate into the anterior chamber of the eye, in strict aseptic conditionsand under general anaesthesia. In group A. cataract was treated by cryo-coagulation and in Groups Band C intra-capsular cryo-extraction of the cataractous lens was performed after pre-medicating and anaesthetising the animals. Surgery for cryo-coagulation (Group A) or intra-capsular cryo-extraction (Groups B and C) was performed under general anaesthesia with thiopentone sodium after premedication with xylazinc hydrochloride. The anaesthesia was found to be satisfactory at the time of induction and during cataract surgery. Extensive lateral canthotomy was found to be necessary in all the animals at surgery in order to ensure adequate exposure of the globe. Rectal temperature and respiration rate dropped slightly post-operatively, but returned to normal values by the second day after surgery. Pulse rate dropped markedly following surgery, but returned to normal by the sixth day after surgery. Total leukocyte count increased slightly 24 hours after surgery. but then decreased and remained within normal ranges thereafter. There was increase in neutrophil. eosinophil and monocyte count had increased upto 24 hours after surgery. but was normal thereafter. Lymphocyte eount decreased upto 24 hours post-operatively. All the animals .remained in good condition throughout the observation period, except for one animal. Conjunctivitis persisted only in one upto the 11 th day. Corneal oedema persisted throughout the period of observation in four animals. One animal had complete corneal clarity by day seven. In the other animal the cornea cleared on day 23. Uveitis persisted for varymg periods in the animals Photophobia and blepharospasm resolved by day six in all animals. One animal had no posterior or anterior synechiae following surgery and its vitreous body was clear, allowing easy exam ination of the retina. Aqueous flare, indicative of increased protein in the aqueous humour, could not be determined in any animal. Functional vision was not returned in any animal except A4. In Group B, vitreous prolapse occurred during surgical removal of the lens by intra-capsular cryo-extraction. This prolapsed vitreous was excised and did not cause complications. Rectal temperature increased slightly 24 hours after surgery, but had returned to normal values by the 15th post-operative day. Pulse rate decreased slightly 24 hours after surgery, but attained normal values by the second post-operative day and stayed so thereafter. Respiration rate decreased markedly for 24 hours following surgery, but reached normal values two days post-operatively. There was no change in the colour of the mucous membrane of the contralateral eye (used as control) at any time during the period of : observation. The total leukocyte count increased slightly following surgery and continued to be so till 24 hours after surgery and thereafter it decreased and was within normal limits thereafter. The neutrophil count increased till 24 hours post-operatively and returned to normal range thereafter. Lymphocyte count decreased slightly 24 hours after surgery, but returned to normal range by the i s" post-operative day. Eosinophil count increased 24 hours after surgery, but had reached normal values by the i s" post-operative day. Monocyte count became zero after surgery, but then increased slightly and continued so thereafter. All the animals remained in good general condition until the end of the observation period, with no evidence of infection in the operated eye. Intra-ocular pressure decreased slightly following surgery, but had returned to normal ranges by the end of the observation period. Animals B 1, B2 and B4 had persistent conjunctivitis and corneal oedema throughout the period of observation and were unable to negotiate an obstacle course or locate and track mobile or stationary objects even in conditions ofbright ambient light. All other animals in this group were able to perform satisfactorily in the tests of visual function by the end of the observation period. In Group C, treatment of cataract was by intra-capsular cryo- extraction, as in Group B. The results obtained were similar to those for Group B. Animal C2, however. took 52 hours to recover from anaesthesia and died on the sixth day following surgery. The death could not be attributed to complications of cataract surgery. Rectal temperature decreased slightly following surgery, and then increased slightly but returned to normal values at the end of the observation period. Pulse rate decreased immediately after surgery and then returned to normal ranges by the eighth day after surgery. Respiration rate decreased markedly immediately after surgery. but returned to the normal range within 24 hours after surgery. Colour of mucous membrane of the contralateral eye did not show any change at any time during the period of observation. Total leukocytc count increased slightly upto 24 hours after surgery but returned to normal ranges thereafter. The neutrophil and eosinophil and monocyte counts increased after surgery but returned to normal ranges thereafter. The lymphocyte count was markedly decreased at 24 hours after surgery, but then returned to normal ranges thereafter. The surviving animal in Group C showed low grade corneal oedema until day 31 following surgery, but it had blink reflexes and the iris was visible. Conjunctivitis had cleared by day six following surgery. The animals were monitored for visual capability following surgery. The tests were conducted by evaluating the animals' ability to negotiate an obstacle course under photopic and scotopic light conditions, after blind folding the left eye with an eye shield. The animals were also tested for their ability to locate a stationary object and to track a moving object under varying conditions of ambient lighting. Tests of ocular functional integrity were conducted by evaluating menace and photomotor pupillary reflexes. Animal Cl was able to locate or track stationary objects In dim light. It could track moving ohjects in all light conditions. From the results obtained in thc present study. it was found that only one out of the six animals showed restoration of functional vision following treatment of cataract by cryo-coagulation of the lens. In the case of the treatment by intra-capsular cryo-extraction. four out of eight animals showed restoration of functional vision thus showing a success rate of 50% for intra-capsular cryo-extraction of cataract. From the results it can be concluded that: 2. Cataract could be effectively induced using 0.5 ml of calcium borogluconate solution (25%) injected into the anterior chamber of the eye. 3. Pre-medication USing xylazine hydrochloride followed by general anaesthesia USing thiopentone sodium IV was satisfactory for the induction of cataract and the treatment of the cataractous lens. 4. Intra-capsular cryo-extraction IS a better method In treating cataractous lenses in dogs.
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171711