Relationship between corneal dellen and tearfilm breakup time.

The BUT of 51 strabismus patients were measured before and after operation. The average pre-op BUT was 28.75 seconds (10.96"-91.80"). The post-op BUT in all operated eyes were reduced significantly, no matter what procedures had been performed and whether dellen appeared or not (P < 0.01). The BUT in the group complicated dellen reduced from 23.22" (pre-op) to 8.61" (post-op). The incidence of dellen was 22.54% in this study. The incidence of dellen after rectus resection procedure (47.75%) was much higher than that after rectus recession (5.13%) (P < 0.01). This study showed that dellen was closely related to the BUT and occurred more often in the eyes on which resection procedure was performed. It is considered that excessive lacrimation and elevation of the bulbar conjunctiva near the limbus may disturb the stability of the precornea tearfilm and cause the tearfilm break up earlier. Local corneal dehydration and dellen formation may be caused by reduced BUT. The incidence of dellen after operation may be higher if the cornea was carefully observed.