Effects of Intracameral Injection of Lidocaine on The Cornea in  A Rabbit Model. Scanning Electronmicroscopic Study

Wafaa S. Ramadan

Anatomy Department , Faculty of Medicine ,  Ain Shams University.

Abstract

         Combined topical and intracameral anesthesia     proved to be  an  alternative to peribulbar and retrobulbar anesthesia in cataract surgery especially in phacoemulsification approach.. So, in the present work the effect of intracameral injection of different concentrations of lidocaine on the  structure of rabbit’s cornea was studied using the freez-fracture technique and the scanning electron microscope . Fourteen baladi  rabbits of both sexes weighing 2-3 kg.were used and divided into two groups  according to the concentration of lidocaine .One eye of the animals of the first group  was injected with 0.2 ml. of 0.5% lidocaine into the anterior chamber  and the other eye with balanced salt solution (BSS)and served as control . In the second group , one eye was injected with 0.2 ml. of 2% lidocaine and the other eye with (BSS) .In both groups the duration of injection  was  10 minutes. Parts of the cornea were prepared for scanning electron microscopic examination. The control specimens showed polygonal epithelial cells with surface microvilli , microplicae and craters. The craters had raised edges with fenestrations and / or microvilli on their floor. Bowman's membrane was acellular homogenous layer.The stromal lamellae were arranged in zip pattern. The keratocytes were spindle-shaped with irregular surface . Descemet's membrane appeared to be splitted. The endothelium was seen as polygonal cells with raised edges and surface micrvilli. With the use of 0.5% lidocaine the endothelial cells became oedematous. On the other hand, with the use of 2% lidocaine there was excessive blebs, bullae and marked oedema of the endothelium with sloughing of some cells.  So, the injection of high concentration of lidocaine into the anterior chamber during cataract operation is a potential risk for endothelial injury that may lead to loss of corneal transparency.However using the low concentration of lidocaine appeared to be safe with no  adverse effects .