The tear film in rheumatoid arthritis
Authors: Craig J. P. , Tomlinson A. , Sturrock R. D. , Grierson D. J. , Patel S. 
Published: July 2002

Dry eye (keratoconjunctivitis sicca, KCS) is thought to develop in approximately 10% of rheumatoid arthritic patients with the most severe examples being found in patients with Sjögren's syndrome (KCS, xerostomia and connective tissue disease). Dry eye is present to a lesser but significant extent in patients with rheumatoid arthritis not associated with Sjögren's syndrome and in a mild form in the ageing population. Diagnosis of dry eye depends on obtaining a careful clinical history from the patient and performing various clinical tests of tear function.

Tear physiology in rheumatoid arthritis has received little attention in the literature. The aim of this study was to investigate differences in basic tear physiology between rheumatoid arthritic patients with and without the association of Sjögren's syndrome by evaluating tear production, stability, evaporation and osmolarity in order to gain more knowledge into the regulatory mechanism of the lacrimal apparatus in these conditions. This study could also prove useful in the long‐term development and evaluation of therapies for dry eye.

Tear production was assessed using Schirmer tear test strips. The Keeler Tearscope™ allowed observation of the lipid layer and evaluation of the non‐invasive tear break‐up time. A modified Servomed evaporimeter provided recordings of the tear evaporation rate and osmolarity was determined by the freezing point depression method.

Rheumatoid arthritic patients with (n = 30) and without (n = 17) the association of Sjögren's syndrome were selected from those attending a rheumatology outpatient clinic. The same set of tests was performed on 25 age‐ and sex‐matched normals. Diagnosis of dry eye for the purpose of this study was based on symptomatic evaluation and on ocular surface staining after instillation of rose bengal eye drops as determined by an independent observer.

Results showed that there is a significantly greater degree of corneal and conjunctival staining in the Sjögren's group compared with the rheumatoid arthritic subjects without Sjögren's syndrome (P < 0.05) and also in the rheumatoid arthritic group compared with the normals (P < 0.05). Tear production rate is not reduced in the subjects with rheumatoid arthritis along compared with the age‐ and sex‐matched normals (P > 0.05), but is significantly reduced in those with Sjögren's syndrome (P < 0.05). Tear evaporation and osmolality were found to increase significantly in both rheumatoid arthritic groups compared with normals (P < 0.05) but there was no significant difference between those with and without Sjögren's syndrome (P < 0.05). An abnormal coloured fringe pattern was detected in no normals, in 10% of subjects with rheumatoid arthritis alone and in 40% of those with Sjögren's syndrome.

A mechanism for the development of dry eye in the rheumatoid arthritic subjects without Sjögren's syndrome is proposed. Reduced integrity of the lipid layer does not inhibit evaporation of the aqueous layer of the tears. This increased evaporation rate leads to increased tonicity of the tears and is though to play a role in the damage to the ocular surface.