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OPHTHALMOLOGY Artificial Corneas, Dry Eye Among Conference IssuesResearchers in ophthalmology had a chance to eyeball their colleagues' latest findings at the 2001 Biennial Cornea Conference, held Sept. 21 to 22 and sponsored by the Schepens Eye Research Institute and Massachusetts Eye and Ear Infirmary. In a Friday morning session on ocular surface topics, May Griffith of the University of Ottawa Eye Institute discussed her group's efforts to create artificial corneas through tissue engineering, both for transplantation and as a replacement for live animals in testing the safety and efficacy of drugs and chemicals. Many countries suffer from a shortage of natural corneas for transplants to treat corneal blindness, Griffith said, and Asia could immediately use an estimated 10 million artificial corneas if they were available. An Organic ReplacementMost scientists working on artificial corneas have used plastic, which is easier to engineer than organic tissue but can cause immune rejection. Griffith and coworkers chose instead to use a scaffold based on collagen, the material from which the natural cornea is built. In contrast to the challenges facing prosthetic corneas, she said, "We started with poor mechanical properties and excellent biocompatibility." Their recent work has been directed at improving toughness, transparency, and other mechanical properties of their corneas by adding synthetic materials and at coaxing nerve cells to grow into the tissue. Griffith said the efforts at innervation have been encouraging.Driss Zoukhri, HMS instructor in ophthalmology at MEEI and Schepens, presented new findings on the role of pro-inflammatory cytokines (interleukin-1 alpha, interleukin-1 beta, and tumor necrosis factor alpha) in the impaired lacrimal secretion seen in Sjögren's syndrome. This is a chronic autoimmune condition that can occur by itself or secondary to diseases such as rheumatoid arthritis, lupus, or scleroderma. In Sjögren's patients, 90 percent of whom are women, lymphocytes invade and destroy moisture-producing glands such as the tear and salivary glands, resulting in dry eyes and mouth and often affecting other organs as well. No Tears FormulaEarlier work by Zoukhri and colleagues suggested that inflammation of the lacrimal glands somehow prevents nerve cells from releasing neurotransmitters, and they believe cytokines might be responsible. In the new studies, using a mouse model of human Sjögren's syndrome, they found that IL-1 beta inhibited lacrimal secretion most strongly. Levels of the protein were upregulated 21-fold in the mice by 13 weeks of age. Their results "suggest that elevated levels of IL-1 beta, as it occurs in Sjögren's syndrome exocrine glands, might impair the secretory function of these tissues thus leading to dry eye and dry mouth," and that antagonists might someday be used as a treatment.At a Saturday poster session, Tomo Suzuki, a fellow in the laboratory of David Sullivan, HMS associate professor of ophthalmology at Schepens, described another Sjögren's study. Working with Debra Schaumberg, HMS assistant professor of medicine at Brigham and Women's Hospital, and using data on nearly 40,000 women from the BWH Women's Health Study, they found that hormone replacement therapy was associated with dry eye symptoms and diagnosed dry eye syndromes. The authors have an upcoming paper on the study in The Journal of the American Medical Association. Claes Dohlman, emeritus professor of ophthalmology at MEEI, introduced a lecture named in his honor Saturday morning. The Dohlman lecturer was Miguel Refojo, emeritus senior scientist, who discussed new developments in extended-wear contact lenses. The new lenses are hybrids that combine the softness and comfort of conventional soft lenses with the high oxygen permeability of rigid lenses, he said. --Tom Reynolds |
