KERATO-CONJUNCTIVITIS sicca is the condition which follows a reduction of secretion by the main and accessory lacrimal glands, and is characterized by interpalpebral staining of the bulbar conjunctiva with rose Bengal, punctate corneal staining with punctate opacities in Bowman's zone, the presence of thick stringy mucous strands in the lower fornices, and corneal filaments, the latter being neither invariable nor pathognomonic. Kerato-conjunctivitis sicca occurs most commonly as a manifestation of Sjogren's syndrome; it is occasionally seen in sarcoidosis due to infiltration of the lacrimal gland, and is rarely due to congenital absence of tears (e.g. the Riley-Day syndrome) or acquired neurogenic lesions of the secretomotor pathways. Sjogren (1933) described the triad of clinical features (rheumatoid arthritis, xerostomia, and kerato-conjunctivitis sicca) and stated that two of the three should be present. It is now recognized that any of the collagen diseases, but particularly disseminated lupus erythematosus (DLE), may replace rheumatoid arthritis in the triad, and that Sjogren's syndrome forms part of the range of connective tissue disorders associated with the presence of autoantibodies (Morgan and Castleman, 1953; Bain, 1960; Robinson, 1963). The frequent poor response to treatment of this disorder is indicated by the variety of methods which have been used, including various artificial tear preparations, local steroids, anticoagulants (Stark, 1961), fibrinolysin (Weve, 1928), debridement of the epithelium, radiation (Winters and Asbury, 1956), systemic hydroxychloroquine (Heaton, 1963), tarsorrhaphy, and contact lenses, while occlusion of the puncta certainly helps to conserve any lacrimal secretion which may be formed. Duke-Elder and Leigh (1965) have concluded that "in the majority of such cases the ophthalmologist is reduced to the expedient of judicious but impotent expectancy". The best available artificial tear preparation appears to be a solution of carboxymethylcellulose at pH 8 5, with added sodium bicarbonate and sodium chloride as devised by Jones and Coop (1965), and this is the standard tear substitute used here. Jones and Coop also reported encouraging results in fifteen patients with keratoconjunctivitis sicca treated with the mucolytic agent acetylcysteine. N-acetyl-L-cysteine is a derivative of the amino-acid L-cysteine and is widely used to reduce the viscosity of mucus in a variety of broncho-pulmonary disorders (Webb, 1962). This reduction in viscosity is achieved by the reducing action of the free sulphydryl group in the molecule on the disulphide bonds of the mucoproteins present in mucus.
