Retrospective analysis of actual LASIK flap diameter compared with microkeratome ring size performed by different...

To evaluate the difference in the diameter between microkeratome ring and actual laser in situ keratomileusis (LASIK) flap size by 4 different surgeons using 3 different microkeratomes in comparison to preoperative keratometry.

Gimbel Eye Centre, Calgary, Alberta, Canada.

A retrospective analysis of 6667 consecutive LASIK surgeries performed at the Gimbel Eye Centre between 1998 and 2002 was conducted. The study compared the difference in the actual LASIK flap diameter and microkeratome ring size for 3 Hansatome microkeratomes indicated by serial numbers 2230, 3048, and 3084 in comparison to the preoperative keratometry. The surgeries were performed by 4 surgeons from the Centre.

A statistically significant correlation was found between the actual flap size and the microkeratome ring size. The deviation increased with corneal steepness (#2230: r = 0.45, P<.001; #3048: r = 0.28, P<.001; #3084: r = 0.23, P<.001). The mean difference between actual flap size and the microkeratome ring size was 0.647 mm, 0.808 mm, and 0.916 mm for Hansatome microkeratome #2230, #3048, and #3084, respectively. The actual flap was larger than the microkeratome ring size in 92.8%, 93.8%, and 97.4% of eyes, respectively. The mean difference between microkeratome ring size and measured LASIK flap size was consistently significantly different (P<.0001) per surgeon for all microkeratomes.

Estimation of the flap size is an important issue while selecting ring size and planning the treatment zone. In this study, the actual flap size was larger than the ring size for all surgeons and all 3 Hansatome microkeratomes. Higher preoperative keratometry values achieved larger flaps than those with lower keratometry values.