Soft contact lens wear in Hong Kong-Chinese: predicting success

The tear stability and tear volume of 55 asymptomatic Hong Kong-Chinese were assessed before soft contact lens (Hydron Zero 6) were and repeated on three visits over 28 weeks of lens wear. Soft lens wear caused a significant initial transient decrease in the non-invasive tear break-up time (NITBUT), but no change in tear volume as assessed by the self-prepared cotton thread test (SP-CTT) and phenol red thread (PRT) test. After 28 weeks, the subjects were classified according to the length of time they could wear their lenses without dry eye related signs and symptoms. The NITBUT and PRT tests were unable to predict the success of soft contact lens wear. However, the SP-CTT gave a sensitivity and specificity of 88.5 and 52.4%, respectively, in the prediction of subjects most likely to be successful wearers. The positive and negative predictive values at the chosen cut-off point were 69.7 and 78.6%, respectively. Wetting values, that is, combinations of NITBUT and SP-CTT values or NITBUT and PRT values, did not predict success in soft contact lens wear.