Comparison of four different VisuMax circle patterns for flap creation after small incision lenticule extraction

To compare four different Circle patterns for flap creation after small incision lenticule extraction (SMILE).

SMILE was performed on six rabbits. Twenty-eight days after the initial procedure, corneal flaps were created using Circle patterns. Rabbits were divided into four groups (patterns A, B, C, and D). Pattern A creates a circular side cut to meet the cap cut within the clearance zone (outside of the optical zone). Patterns B, C, and D create a lamellar ring posterior, anterior, and at the same depth, respectively, to the cap to meet the cap cut in the clearance zone with the help of a junction cut. Difficulty of flap lift was graded from 1 (easiest) to 5 (most difficult). The bed quality was assessed by scanning electron microscopy.

Flaps created by patterns A and D were the easiest to lift (grade 2). The resulting flap bed was smooth and undisrupted. However, pattern A resulted in a reduced re-treatment area. Flaps created by pattern B were the most difficult to lift (grade 4). The stromal dissection was difficult in an attempt to ascertain the original optical zone from the lamellar ring, placed posterior. Flaps produced by pattern C were easy to lift, with minor intrastromal resistance experienced during the lifting process (grade 3). The transition between the lamellar ring and cap cut was hardly discernible in pattern C-treated corneas.

Pattern D, a lamellar ring adjacent to the cap cut, was the most optimal to be used for flap creation in cases of SMILE re-treatment.