97th DOG Annual Meeting 1999



G. Geerling1, 2, A. Poon1, J. T. Daniels2, I. A. Cree1, 2, J. K. G. Dart1, 2

Background: In severe ocular dryness the corneal and conjunctival epithelium is not only depleted of the lubrication necessary to reduce blink induced shear forces, but also protective and nourishing factors such as EGF and Lysozyme. The symptoms and signs of the resultant severe ocular surface disease may be poorly relieved by simply replacing the aqueous component when using pharmaceutical tear substitutes. Serum drops or a microvascularly transplanted autologous submandibular gland (SMG) can be used to replace lubrication and endogenous nutritional factors. Their effect on ocular surface epithelium was evaluated in a laboratory and clinical study.

Methods: Human corneal epithelial cells were cultured with a defined serum free medium to subconfluency and exposed to serum drops (serum/chloramphenicol = 60/40 VW), SMG saliva and various pharmaceutical tear substitutes for varying duration. The viability of the cultured cells was assessed using a luciferase based ATP-assay and fluorescent staining (Calcein-AM/Ethdium-homodimer). In 8 patients who received drops of serum and 5 patients (5 eyes) with a SMG transplant, symptoms and signs (Rose Bengal and Fluorescein staining) were assessed. Conjunctival squamous metaplasia and corneal epithelial morphology were graded using impression cytology.

Results: After 24 hours morphology and ATP levels were best maintained in cultured human corneal epithelial cells exposed to serum drops. SMG saliva induced delayed cell death, which could be significantly reduced by adjusting the osmolality of the naturally hypotonic saliva to isotonicity. Preserved as well as unpreserved hypromellose induced a higher rate of cell death. One month after the initiation of autologous serum eye drops 5 of 8 patients showed improvement of Rose Bengal staining and discomfort. All eyes with functional SMG transplants showed a reduction of dry eye signs and symptoms. In one of those eyes a microcystic corneal epithelial oedema evolved.

Conclusion: Tear substitutes from serum or isotonic SMG saliva preserve cultured epithelial cells better than pharmaceutical tear substitutes. Both offer new and successful therapeutic approaches in the treatment of aqueous as well as nutrition deprived dry eyes. While serum drops are available for a wide range of patients, SMG transplantation remains an extensive operation, reserved for only the most severely dry eyes. (Supported by DFG Ge /4-1)

1Moorfields Eye Hospital, City Road,
2Institute of Ophthalmology, Bath Street, London, UK