Abstract
Abstract: :
Purpose:The purpose of the study was to identify cells that migrate into the posterior segment of the rabbit eye after intravitreous injection of Vitrase. Methods:Eighteen rabbits were examined by indirect ophthalmoscopy (I.O.) and slit-lamp biomicroscopy. The animals were anesthetized and sixteen rabbits (N=16) received intravitreous injections of 75 IU of Vitrase, OU (equivalent to twice the human clinical dose). Two rabbits from this group were randomly selected on Days 0, 1, 2, 4, 7, 10, 14 and 28 and re-examined by I.O. and slit lamp biomicroscopy. The animals were then sacrificed and the eyes were enucleated and processed for paraffin sectioning and immunohistochemical staining. The remaining animals received either sham injections into the vitreous (N=1) or saline injections (N=1), OU, sacrificed, enucleated and tissue was taken for processing. Tissue sections were probed with antibodies specific to rabbit activated macrophages, T-lymphocytes and B-lymphocytes. Results:Ophthalmoscopic observations of eyes injected with Vitrase identified haze and cells in the vitreous 2 - 28 days following injection. These are clinical indicators of an inflammatory response. The cells were observed by light microscopy, in the body of the vitreous and near the retina. Immunohistochemical staining showed that these cells were composed of activated macrophages, T-cell lymphocytes and B-cell lymphocytes. Activated macrophages were present on Day 2, and all cell types appeared by Day 4 and became more numerous through Day 14. At Day 28, microscopic and ophthalmoscopic observations showed that the cellular response in the posterior segment was diminished to levels observed at Day 4. Conclusion: The presence of macrophages in the vitreous suggests that the initial inflammatory response by the rabbit following a single Vitrase injection is cellular in nature. The presence of T-lymphocytes and B-lymphocytes suggests the possibility that a humoral response may be elicited, but this has not been observed in other species.