Visual Recovery After Corneal Lenticule Extraction For Advanced Refractive Correction (Clear) In Relation To Laser Power Settings.

This study aimed to investigate the early visual outcomes of CLEAR in relation to laser power settings used during the surgery.

A retrospective, single-site, consecutive case series study. All patients were treated with CLEAR at the First Samsung Eye Center in Seoul, South Korea.

706 eyes (358 patients) with mean preoperative spherical equivalent of −4.37 ± 1.78 diopters underwent CLEAR treatment using the FEMTO LDV Z8 laser (Ziemer Ophthalmic Systems AG). Patients were examined preoperatively, 1 day, 1 week, 1 month and 3 months after the surgery. Uncorrected distance visual acuity (UDVA) and corrected distance visual acuity (CDVA) were evaluated at each follow-up visit as a function of laser power settings used during the surgery: initial laser power to ensure smooth lenticule interfaces’ dissection (Group 1), optimal laser power to ensure smooth lenticule interface’s dissection with minimal gas bubble layer formation in the interface (Group 2) and laser power close to stroma ablation threshold (Group 3).

40.4% of all eyes had UDVA of 20/20 or better at 1 day, 69.2% at 1 week, 82.6% at 1 month and 84.0% at 3 months. Postoperative UDVA (in decimal notation) at 1 day, 1 week, 1 month and 3 months was 0.83 ± 0.25, 0.93 ± 0.20, 0.95 ± 0.18 and 1.05 ± 0.09 in Group 1, 0.88 ± 0.25, 1.03 ± 0.24, 1.09 ± 0.23 and 1.14 ± 0.22 in Group 2 and 0.85 ± 0.26, 1.03 ± 0.25, 1.10 ± 0.22 and 1.15 ± 0.22 in Group 3. CDVA was 0.88 ± 0.16, 1.10 ± 0.10, 0.99 ± 0.16 and 1.15 ± 0.09 in Group 1, 0.92 ± 0.24, 1.09 ± 0.23, 1.15 ± 0.21 and 1.27 ± 0.13 in Group 2 and 0.93 ± 0.25, 1.11 ± 0.24, 1.18 ± 0.19 and 1.23 ± 0.20 in Group 3. One-way ANOVA between groups did not show any statistically significant difference in neither UDVA, nor CDVA at any follow-up visit.

Although we did not observe statistically significant difference with regard to visual outcomes between the groups, we recommend avoiding using laser power value close to stroma ablation threshold in order to avoid potential complications with regard to tissue separation and lenticule removal, which could ultimately impact visual outcomes in individual patients. In fact, when we lowered the laser power close to the stroma ablation threshold we observed few cases of increased adhesions and difficult lenticule tissue separation. The very low pulse energy and overlapping spots used in CLEAR application combined with optimal laser power value (Group 2) should ensure smooth lenticule interfaces dissection and a fast visual recovery.