Preocular tear film characteristics of nonwearers and soft contact lens wearers.

Abstract

The aims of the current investigation were to: (1) characterize (structure, volume, and stability) the preocular tear film of contact lens wearers and nonwearers and (2) test for any difference between contact lens wearers and nonwearers and between symptomatic and asymptomatic subjects. The tear film structure and stability were tested using the Tearscope in conjunction with the biomicroscope observation system. The tear prism height, which is indicative of the tear volume, was measured with the slitlamp. The study was carried out on 239 subjects (478 eyes) who attended our clinic for contact lens fitting. Of these, 184 were habitual daily soft contact lens wearers who had not been wearing contact lenses for at least 24 h; the other 55 were noncontact lens wearers. The results obtained showed that: (1) the stability of the tear film was correlated for two eyes of the same subject; (2) the structure, volume, and stability of the preocular tear film were similar for both groups; (3) no difference in tear film stability was found between asymptomatic and symptomatic contact lens wearers, but a significant difference was found between asymptomatic and symptomatic noncontact tact wearers; and (4) the stability of the tear film was influenced by the nature of the lipid layer present at the surface of the aqueous layer; the greatest stability was achieved when the lipid layer was thick and homogeneous (amorphous pattern).