MECHANICAL MANIPULATION OF THE LIDS AND TEAR BREAK-UP TIME MEASUREMENTS IN HONG-KONG CHINESE

We measured tear break-up time (TBUT) after lid-rubbing in a single ma sked experiment, and found that TBUT was unaltered. A further single m asked experiment in which non-invasive tear break-up time (NITBUT) was measured after the lids were raised as if to apply fluorescein also s howed no effect of this interference with the lids. An experiment in w hich fluorescein was applied either with the lid raised or not raised during fluorescein application, again with the experimenter masked wit h respect to treatment, also produced no significant difference in TBU T. When we measured TBUT with the lid raised so that it was not in con tact with the cornea, there was no difference in TBUT for the group be tween the 'lifted' and 'non-lifted' eye; some subjects showed substant ially shorter TBUT values, while others showed substantially longer TB UT values. These findings are surprising in view of the concerns expre ssed in the literature regarding the sensitivity of the tear film to m echanical interference, and suggest that the tear film is more resista nt to disruption than has previously been thought.