discovering dry eye
New Technology Meets Dry Eye
BY KELLY KINNEY NICHOLS, OD, MS
Recently I read an interesting journal article describing a treatment for severe dry eye cases transplantation of autologous submandibular gland into the lacrimal fossa with microvascular anastamosis. Imagine...saliva-like replacement tears. At first I read the article with disbelief, but as I mulled over the alternative treatments for severe dry eye, the concept became intriguing and thought-provoking. Is this where new technology meets dry eye?
Why should the concept of submandibular gland transplantation seem so foreign? After all, burn patients undergo extensive skin grafts, organ transplantation saves lives daily, and corneal transplantation significantly improves the quality of vision. I like to think of an even trade with transplantation: heart replaces heart, cornea replaces cornea. Placing the submandibular salivary gland in the location of the lacrimal gland seems incongruous to me. To my knowledge, transplantation of a lacrimal gland has not been attempted.
Submandibular Gland Transplantation
The purpose of the previously mentioned study was to evaluate the quality and composition of pre-ocular fluid produced by the transplanted submandibular gland in patients with severe dry eye. Researchers examined 15 patients with viable transplantation, compared collected tears to tears and submandibular gland saliva from 20 healthy controls, evaluated saliva and tear ferning patterns and assessed tear proteins.
The authors found that the composition of submandibular gland tears differs significantly from normal tears; however, submandibular gland tears are more similar to normal tears than submandibular gland saliva. Higher concentrations of secretory IgA, lysozyme and amylase are found in submandibular gland tears (although found in lower concentrations in normal tears). Detailed studies of submandibular gland tears are ongoing.
A New World
Recently, full-thickness functioning corneas have been grown from immortalized human cor-neal cells. The resulting corneal equivalents (epithelium, stroma, and endothelium) mimic human counterparts in many physiological functions including ion and fluid transport, biochemical marker expression and transparency (Griffith et al., Science, 1999). This research is remarkable in that these grown corneas may someday be available for drug testing and transplantation.
Given these recent advances, one can almost envision lacrimal gland acinar cells grown in tissue culture in the lab and subsequent transplantation onto a lacrimal gland ravaged by Sjögren's disease. This sound like a far-fetched science fiction movie; however, I would wager that talented scientists and surgeons have considered the possibility.
Science Fiction Vs. Science
Bioengineering is a complex field both scientifically and ethically. In our example of transplanted acinar cells, what if the cells were grown from cells from a family member? Most individuals would not have a problem with this ethically. Perhaps the procedure would be viewed differently if it was possible to transplant cell lines from a different animal. With bioengineering and genetic medicine growing rapidly, ethical issues will continue to reach the media spotlight. While these issues do not affect the profession of vision to a great extent today, the future is unforeseen. Will new technology ever meet dry eye? For our patients' sakes, we can hope so.
Dr. Nichols is a graduate research associate at The Ohio State University College of Optometry in the area of dry eye research.