Forecasting of hydrophilic contact lens tolerance by means of tear ferning test

Background: The ability of the tear ferning test to predict future hydrophilic contact lens tolerance was studied. Methods: The tear ferning test (TFT) was performed on one randomly chosen eye of each of the 116 subjects who came to our contact lens clinic for hydrophilic contact lens application. The TFT was performed at the time of enrollment (T0) and then 1 month (T1), 3 months (T2) and 6 months (T3) after contact lens fitting. The specificity and the sensitivity of the TFT in identifying future contact lens tolerance was then studied. The statistical significance of the differences in behavior through the study period among the subjects with different pre-fitting TFT results was evaluated by means of survival curves. Results: When only type I ferning was considered as a marker of good tear film conditions, the ability of the TFT to forecast contact lens tolerance had 78.95% sensitivity, 78.35% specificity and 78.45% diagnostic precision. The TFT showed sensitivity of 100%, specificity of 86.6% and diagnostic precision of 97.4% when performed after 1 month of contact lens wearing (T1). Survival curve analysis showed a statistically significant difference in behavior between the group of subjects with pre-fitting ferning type T and the other three groups (P<0.001). Conclusion: The TFT appears to have good sensitivity and specific for prediction of contact lens tolerance in a clinical setting.