The impact of corneal tear quality and tear quantity on deposits to soft contact lenses
J. Stahn, U. Fiedler, W. Behrens-Baumann
Introduction: Many patients wearing soft contact lenses (SCL) complain about discomfort. Often we find deposits on the lenses, which consist of tear film molecules. Aim of this study was to investigate deposits on SCL in regard to the tear secretory rate in patients.
Methods: Patients wearing SCL were divided into two groups: 22 individuals with a normal tear secretory rate (Schirmer I > 15mm, BUT > 10sec, referred as control group - CG) and 21 individuals with pathological tear secretory rate (Schirmer I < 15mm, BUT < 10sec; referred as sicca group - SG) . All patients used the same cleaning solution for the SCL. In addition, the SG were given artificial tears. Over 12 months we assessed deposits to the SCL by dark field microscopy. The conjunctival swab and the storage container were analyzed for microbiological contamination. All patients were assayed for wearing time and comfort.
Results: In 10 patients of the CG group, we found extensive deposits on the SCL, where as in the SG only 6 lenses showed such deposits. Deposits were mostly localized at the imprint site of the lens, some deposits covered a larger area. In 2 cases in the CG we terminated the study earlier, due to excessive deposits on the lens. No correlation between bacterial contamination, particular deposit grade of the lens and/or the cleaning solution was found. Patients in the SG complained more frequently about dry eyes and foreign body feeling then patients in the CG. In two cases this led also to an earlier termination of the study. The CG patients worn the SCL in average 76 hours/week, where as the SG used them only 53,5 hours/week.
Conclusions: We think, that the lower grade of deposit material on the lenses in the SG is directly associated with the shorter exposure time to the ocular tear film. Among other factors, the subjective wearing comfort of SCL is also dependent of sufficient corneal tear production and moistening of the SCL. Only minor deposits on the SCL have no negative impact on the subjective wearing comfort.
Department of Ophthalmology, Otto-von-Guericke-University Magdeburg, Leipziger Str. 44, D-39120 Magdeburg, Germany