Corneal topography changes at different time of fixation after blinking

Objective To analyze and compare the changes of corneal topographic parameters at different time of fixation after blinking between non-dry eyes and dry eyes and to investigate the optimal time between the last blink and the acquisition of topographic image. Methods Thirty non-dry eyes and 30 dry eyes were examined using corneal topography system. Photographs were taken at 5, 15 and 30 seconds after a complete blinking in non-dry eyes and were taken at 5 seconds after the last blinking in dry eyes. The main outcome measures were corneal irregularity measure (CIM) and shape factor (SF). Results The mean values of CIM increased significantly during the 30 seconds pause in blinking in non-dry eyes (P ＜0.05). The mean of CIM and SF values were 1.15± 0.55, 0.28± 0.14 at 5 seconds after the last blink in dry eyes, respectively. The mean values of CIM was significantly greater than that at 5S after a complete blinking in non-eyes (P＜0.01). Conclusions The accuracy of the corneal topography system is closely related to the time of fixation after blinking. It is proposed to perform the topographic measurements within 5 seconds after the last blink. The regularity of corneal surface is correlated with the smooth of the tear film. Key words: Blink;  Corneal topography;  Corneal surface;  Dry eye