Morphological changes after corneal stromal lenticule excimer laser shaping.

The present study aimed to investigate the feasibility and design of producing a parallel/concave lenticule using an excimer laser on a convex corneal matrix lenticule . Optical coherence tomography was used to measure the thickness of the corneal stromal lenticules. Lenticules were cut using an excimer laser. The lenticules were divided into three groups: 1:1, 1:1.5 and 1:2 cuttings. After cutting, the lenticule thickness was measured again. Thickness changes in the three groups were compared before and after the cuts. Significant differences were observed among the three groups in central thickness, thickness changes (1.5 mm) and the difference between central thickness and thickness (2 mm from the centre) before and after cutting. However, thickness changes at 2 and 2.5 mm from the centre were not statistically significant. The differences between the central thickness and thickness at 2 mm from the centre after shaping (with interquartile ranges) were as follows: 38 (28, 53.5) µm in Group Ⅰ, 6 (-3,15.5) µm in Group II and -10 (-16.5, -5) µm in Group III. In conclusion, excimer cutting at different proportions affected thickness changes at the centre and 1.5 mm from the centre. Furthermore, it did not affect the thickness change at 2 and 2.5 mm from the centre. The lenticule obtained by a 1:1 cutting ratio was convex and the lenticule formed by a 1:1.5 cutting ratio retained a convex shape. However, the centre was very close to the parallel lenticule. The lenticule obtained using a 1:2 cutting ratio was concave.