February 2009




Second laser pass for incomplete flaps could cause irregularities



Researchers persuaded against performing a second femtosecond laser pass for incomplete flaps in the January issue of the Journal of Cataract & Refractive Surgery.

Takeshi Ide, M.D., Ph.D., Bascom Palmer Eye Institute, Miami, and his colleagues determined that using the femtosecond laser a second time may have only a small effect, but it should be avoided, especially in patients in which the opaque bubble layer (OBL) has cleared in the central or inferior cornea because these areas are critical for visual quality.

For the study, 20 porcine eyes were assigned to four groups. In the first two groups, a flap was created with a femtosecond laser with a centrally black-painted applanator 200 microns deep. Then they created a second flap at 400 microns deep using the applanator. The difference between the first and second groups was that in the first group, the surgeons did not wait for the OBL to clear.

In the third and fourth groups, the eyes were separated into those with and without OBL; however, the same depth was used for the second pass after intentional suction loss to simulate a potential complication during surgery.

They reported that in the first group, they could see the peripheral shallow cut and the central deep line and there was significant resistance during the flap lift. The second group had two parallel lines indicating dual flaps that were connected centrally. These results indicate that the OBL may absorb, reflect or block the femtosecond laser energy, and the OBL’s density may be a factor causing an irregular flap.

In the final two groups, however, there were similar results regardless of the OBL’s presence. Both of the final groups had lines on the stromal bed and posterior flap. They also felt resistance when lifting the border of the first femtosecond laser flap possibly because the flap had some irregularities.

“Considering our experience, it may be true that suction can be reapplied easily into the same position due to the shape-memory features of the cornea and sclera,” Dr. Ide said in the study. “As this study shows, however, there can be an irregular surface, multiple flaps, a free sliver of the corneal stroma, and crossing of the two cut planes because of differences in applanation pressure, hydration conditions and chemosis.”

Reported by: EyeWorld News Services

Second laser pass for incomplete flaps could cause irregularities Second laser pass for incomplete flaps could cause irregularities
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