Electron microscopy of corneal surface microdiathermy

Microdiathermy has recently been shown to be effective in the treatment of persistent corneal epithelial recurrent erosion. In order to determine the mechanism of action of microdiathermy on the anterior surface of the cornea, rabbit eyes were treated with microdiathermy and the course of corneal tissue repair studied by electron microscopy. Shortly after treatment, the epithelium is edematous and necrotic and the lamina densa is thickened. Within 24 hours, the epithelium appears healed and some hemidesmosomes are present, but the lamina densa is still thickened. At two weeks the epithelial surface is undulated and protrudes into the stroma in areas where the lamina densa is disrupted. Hemidesmosomes are absent in these regions. Activated fibroblasts are present in superficial stroma. At four weeks following microdiathermy, there is segmental deposition of new lamina densa and a connective tissue zone between the newly deposited lamina densa and the old lamina densa. Hemidesmosomes are present only in areas of newly deposited lamina densa. Between six weeks and three months the epithelial basal surface becomes more uniform with mature hemidesmosomes and the new lamina densa is complete. The old lamina densa remains below it but is no longer present by six months. The mechanism of action for microdiathermy in recurrent erosion is believed to be as follows: in the treated area, epithelium and activated fibroblasts secrete a new connective tissue layer, which provides a suitable substrate to which the epithelium can adhere until it secretes a new lamina densa and hemidesmosome formation can occur.