Submandibular gland transplantation for the severely dry eye. Part II - The ophthalmological experience

This article summarises the ophthalmological experience with 27 eyes to which an autologous submandibular gland (SMG) was transplanted for the treatment of severe keratoconjunctivitis sicca (KCS). Two patients did not attend postoperative controls, but reported a lasting strong relief of symptoms and were able to substantially reduce the use of pharmaceutical tear substitutes. Of the remaining 25 glands 19 were judged viable on 99m- Technetium-Scintillography one year after transplantation. 16 of these eyes had a Schirmer-Test result of ≥5 mm (13 eyes ≥15 mm). Thus 18 of the 27 transplants produced a sufficient amount of salivary tears to significantly improve symptoms of KCS and the need for pharmaceutical tear substitutes. In 10 eyes an excessive epiphora required surgical reduction of the transplant at 1 year postoperative. No gustatory reflex salivation was observed. The secretion could be stimulated by local hyperthermia or physical activity, suggesting that in the absence of a regular innervation the volume of the secretory flow is mainly controlled by the amount of blood flow through the gland. One year postoperative mean Rose Bengal staining of the ocular surface was significantly reduced in patients with a viable graft. However, 5 out of the 10 eyes with excess secretion presented with a diffuse microcystic epithelial oedema. Therefore the composition of the resulting ocular lubrication was analysed. Biomicroscopy regularly showed a mixed seromucinous composition of the salivary tears. Analysis of saliva and tear-specific proteins and electrolytes revealed a composition intermediate between normal tears and normal SMG-saliva. The salivary tears showed concentrations of antibacterial proteins such as Secretory Immunoglobulin A or lysozyme and electrolytes which were significantly higher than in normal saliva, but also still significantly lower then in normal tears. We suspect that the hypotonicity of the salivary tears is responsible for the epithelial oedema observed in some eyes. We are currently investigating the long term effect of saliva on the corneal epithelial barrier function in a clinical and laboratory study. So far, our experience suggests that the transplantation of an autologous SMG is a suitable approach for eyes with severe KCS in which all other conservative and surgical measures have failed to achieve a sufficient comfort and lubrication.