[Tear Osmolarity in Patients with Severe Dry Eye Syndrome Before and After Autologous Serum Treatment: a Comparison with Tear Osmolarity in Healthy Volunteers].

Introduction: Dry eye syndrome (DES) is a multifactorial disease of the tears and ocular surface. Recently, treatment with autologous serum eye drops (AS-ed) has been frequently used in these patients. Significant improvement correlates well with clinical, laboratory and subjective findings. It is assumed that one of the key factors in the development of the disease is increased tear osmolarity. The aims of our study were to test tear osmolarity measurements in clinical practice, to examine if osmolarity values differ before and after a 3-month application of 20% AS-ed, and to determine if the values differ between patients with severe DES and healthy individuals.

Methods: The study included 35 patients with severe DES (Schirmer test<5 mm/5 min) and 23 healthy volunteers. Tear osmolarity values (TearLab Osmolarity System), the Schirmer test (ST1), vital ocular surface staining and subjective feelings (the OSDI questionnaire) were assessed in patients with DES before and after treatment with 20% AS-ed. Further, the tear osmolarity values were compared between healthy subjects and patients with DES before and after treatment with AS-ed.

Results: The values of OSDI and vital staining significantly decreased in patients with DES after the treatment (p<0.0001). ST1 and tear osmolarity did not change significantly after the treatment. ST1 values in healthy individuals were significantly higher (p<0.0001) and the OSDI values significantly lower (p<0.0001) than the results obtained in patients before and after treatment. Tear osmolarity was not statistically different between healthy subjects (306 mosmol/l) and patients with DES (302 and 301 mosmol/l before and after treatment respectively).

Conclusion: We demonstrated a positive effect of AS treatment on the ocular surface in patients with DES. However, the osmolarity values did not differ before and after treatment with AS, and they also did not differ significantly between DES patients and healthy individuals. In accordance with other recent studies, our results raise questions concerning the value of the TearLab Osmolarity System for evaluating therapeutic effect and also as a tool for DES diagnosis.