Correction Of Myopic Astigmatism With Corneal Lenticule Extraction For Advanced Refractive Correction (Clear).

To evaluate the outcome of CLEAR treatment in patients with low to high degrees of myopic astigmatism.

A retrospective, single-site, consecutive case series study. All patients were treated with CLEAR at the Universal Eye Center Taiwan (Taipei).

40 astigmatic eyes (20 patients) with mean preoperative sphere of −5.78 ± 1.19 diopters (D) (range: -1.75 to -10.00 D) and cylinder of −1.19 ± 0.58 D (range: -0.25 to -2.25 D) underwent CLEAR treatment using the FEMTO LDV Z8 laser (Ziemer Ophthalmic Systems AG). Intraoperative adjustment for cyclotorsion and lenticule centration on the first Purkinje reflex was performed in all cases by marking the cornea under the surgical microscope with an image-guided system. The manifest cylinder accuracy at 1 week after the surgery was evaluated according to the amount of preoperative manifest cylinder, i.e. low (-0.75 to -1.00 D), moderate (-1.01 to -2.00 D) and high (-2.01 to -3.00 D).

One week after the surgery, the mean total cylinder power was reduced to -0.24 ± 0.31 D with 84% of eyes achieving ≤ 0.50 D and 100% of eyes achieving ≤ 1.00 D. The mean postoperative manifest cylinder in low, moderate and high astigmatism groups was -0.30 ± 0.29 D, -0.22 ± 0.31 D and -0.25 ± 0.31 D, respectively. No astigmatism undercorrection was observed for both moderate and high astigmatism corrections, where the correction index was 1.11 ± 0.20 and 0.99 ± 0.07, respectively. Data analysis for target-induced versus surgically-induced astigmatism prompts no need for a specific cylinder nomogram.

CLEAR shows a high accuracy of astigmatism correction in low to high degrees of myopic astigmatism. Contrary to results of other lenticule extraction procedures reported in the literature, CLEAR doesn’t present an increasing degree of cylinder undercorrection with increasing preoperative manifest cylinder. The accurate astigmatism axis and first Purkinje reflex marking performed under the operating microscope with an image-guided system, the easy centration and cyclotorsion compensation after docking and a stable suction that avoids all the non-cyclotorsional components of eye rotation and suction loss complications are all considered to be key factors contributing to the high accuracy of the astigmatism correction.