VISUMAX cap and flap thickness and optical density evolution after SMILE or LASIK for myopia correction
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First Author: A.Parafita Fernandez SPAIN
Co Author(s): J. Alió del Barrio M. Cantó-Cerdán M. García-González M. Teus J. Alió
To compare the cap and flap thickness and the stromal optical density evolution during a 3-month follow-up with the same Visumax® femtosecond laser (FSL) for performing SMILE or LASIK to correct myopia. The Amaris® excimer laser was used for LASIK ablations.
Vissum (Grupo Miranza), Alicante, Spain.
Prospective, observational, single-center study, comprising 39 consecutive eyes in each group (SMILE/LASIK). An anterior segment optical coherence tomography (AS-OCT) (MS-39,CSO) was made in each visit (1 day, 1 week, 1 and 3 months). Measurements were taken using the caliper. The same observer measured the cap/flap thickness at the center, and 500 microns nasally and temporally. The average value was considered the mean central thickness (MCT). Using ImageJ® software, the optical density (gray scale units (GSU)) was measured in the stroma of the flap/cap, in the residual stromal bed (RSB), and another including both the flap/cap stroma.
Mean central thickness in SMILE caps and LASIK flaps showed statistically significant differences during follow-up. Cap MCT at 1 day,1 week, 1 and 3 months was 127.07±8.42µm, 129.98±10.84µm, 128.77±9.15µm and 131.0±7.83µm, respectively (P=0.01). Flap MCT at 1 day, 1 week, 1 and 3 months postop was 105.29±8.92µm, 104.99±7.37µm, 107.52±7.33µm and 111.19±8.54µm, respectively (P=0.01). Optical density showed a statistically significant change during SMILE follow-up for cap 48.96±5.55GSU vs 44.95±5.41 GSU (P=0.0001), residual stromal bed 50.26±7.06 vs 45.42±7.53GSU (P=0.0001), and total 50.34±6.49GSU vs 45.46±6.96GSU (P=0.0001) at 1 day and 3 months respectively. No significant changes were found in OD during LASIK follow-up.
Both SMILE caps and LASIK flaps presented a significant regrowth during the follow-up, as previously seen in other studies. SMILE corneas showed higher optical densities in the first follow-up visit, with a significant decrease after 3 months, whereas LASIK corneas showed a non-significant decrease in optical density. This early high optical density values might be related to the surgical manipulation during SMILE to remove the lenticule.