Complement levels in human tears

The single radial immunodiffusion technique was modified to determine tear complement component C3 with small sample volume. The C3 levels in the tears from 18 normal subjects and 42 patients with ocular diseases were determined using this method. In the normal subjects, the mean level of tear C3 was 5.12 mg per 100 ml. The physiological level of tear C3 was estimated to be less than 10 mg per 100 ml from the results in normal subjects and patients with noninflammatory ocular diseases. The cases of severe inflammatory diseases such as antiviral keratoconjunctivitis, herpetic keratitis and acute catarrhal conjunctivitis showed a high level of C3 in the tears. The C3 level was relatively low in the cases of mild inflammatory diseases such as allergic conjunctivitis. These results indicated that protein concentration of C3 in the tear was proportional to the severity of inflammation of the anterior ocular segment.