Pathomorphological characterization of lens capsule tissues in animals after prevention of secondary cataracts: an experimental study

One of the current problems of veterinary science is the treatment and prevention of pathologies that reduce the working and productive qualities of especially valuable animals. In veterinary ophthalmology, it remains an important goal to find ways to prevent secondary cataract after ultrasound phacoemulsification. Different methods are used for this purpose, but the questions about pathomorphosis of secondary cataract and scientific basis of effective methods of its prevention remain open. In the present work morphologic changes in the lens capsule of rabbits 2 and 6 months after phacoemulsification under different methods of secondary cataract prophylaxis were identified for the first time. On the basis of clinical picture together with morphological changes the most effective method of prophylaxis - capsulorhexis of the posterior lens capsule - was established. The aim of the work was to study the features of morphological changes occurring in the lens capsule in rabbits after phacoemulsification combined with intraoperative techniques of secondary cataract prophylaxis. The study was carried out in 2020-2021 at the Skryabin Moscow State Academy of Veterinary Medicine and Biotechnology named and at Dr. A.G. Shilkin Veterinary Ophthalmology Center on 18 crossbred rabbits ( Oryctolagus cuniculus domesticus ) of both sexes, aged 4 months, without ophthalmic pathologies. The animals were divided into three groups (6 animals in each group). Ultrasound phacoemulsification was performed in all groups according to the generally accepted technique. Animals of group 1 were implanted with intraocular lens (AquaFree Y-PL, hydrophobic, Overal Dia 13.0 mm, Rumex, USA), group 2 - with intracapsular ring (polymer ophthalmic intracapsular ring for lens bag spreading and lens capsule tensioning, KPV-“ETP-MG” ring No. 3, 13.0 mm, Federal State University Cross-Sectoral Research and Technology Centre, Acad. Fedorov Eye Microsurgery Rosmedtechnologiya-ETP-MG, Russia). In group 3 posterior capsulorhexis was performed. In the postoperative period, the rabbits received general (enrofloxacin, 5 mg/kg body weight, 2 times per day; ketoprofen, 3 mg/kg body weight, 1 time per day for 3 days) and topical treatment (atropine for 10 days; moxifloxacin, eye drops for 14 days; dexamethasone + neomycin + polymyxin B sulfate for 14 days; nepafenac for 28 days). The animals were under continuous monitoring, during which ophthalmologic examination and photographic fixation of the eye condition were performed. Signs of secondary cataract were identified by using slit-lamp biomicroscopy, the state of the ocular fundus was examined by ophthalmoscopy, and the transparency of the capsule was determined. The rabbits were subjected to drug euthanasia 2 and 6 months after the surgery, by 2 and 4 animals, respectively. Eyeballs were enucleated and placed in 10% neutralized formalin solution. For macroscopic evaluation of the state of the lens capsule, a slice was made in the area of the serrated edge of ora serrata with retinal capture. Most of the vitreous body was aspirated. After photography, a sagittal section of the eye was performed and subjected to histologic examination. It was found that within 2 months after performing the above techniques, proliferation of lens epithelium resumes in the capsule, lens fibers are formed (mainly in the area of the equator of the capsular bag), and adhesions with the iris may develop. Within 6 months, the changes progress, however, to a different degree depending on the technique used. It is shown that capsulorhexis of the posterior lens capsule is the most effective technique for secondary cataract prophylaxis due to a limited impact on tissues in general, absence of alien objects after the surgery and, therefore, the least proliferation of pathological lens tissues with preservation of optical transparency of the central region of the capsular bag.