Accuracy Of Corneal Lenticule Extraction For Advanced Refractive Correction (Clear) For Correction Of Myopic Astigmatism With Astigmatism Axis Marking Using An Image-Guided System.

To evaluate the accuracy of CLEAR in correcting myopic astigmatism with Purkinje reflex as a reference point for lenticule centration and cyclotorsion compensation using an image-guided system.

Initial single-site surgical experience with CLEAR (Central Seoul Eye Center, Seoul, South Korea).

Initial 37 astigmatic eyes (19 patients) with mean preoperative sphere of −3.74 ± 1.21 diopters (D) (range: -1.50 to -6.50 D) and cylinder of −1.04 ± 0.58 D (range: -0.25 to -2.25 D) underwent CLEAR treatment using the FEMTO LDV Z8 low-energy femtosecond laser (Ziemer Ophthalmic Systems, Switzerland). Patients were treated with cyclotorsion compensated CLEAR and lenticule centration on Purkinje reflex. Astigmatism axis marking was performed under the operating microscope: the reference astigmatic axis was marked using an image-guided system, followed by Purkinje reflex marking on the cornea with ink. Refractive astigmatic changes were analysed by the Alpins method.

One month after surgery, mean cylinder power was reduced to -0.26 ± 0.30 D with 89% of eyes achieving ≤ 0.50 D. The magnitude of the surgically induced astigmatism (SIA) was 0.90 ± 0.54 D and was slightly lower than that of the target induced astigmatism (TIA) 1.04 ± 0.58 D. 84% of eyes achieved a refractive astigmatism angle of error between ± 5 degrees. The corrected index (CI) was 0.91 ± 0.47. In eyes with preoperative cylinder of ≤−1.00 D the CI was 0.96 ± 0.58.

We found CLEAR to be very accurate for the treatment of patients with myopic astigmatism when taking Purkinje reflex as a reference point for lenticule centration and cyclotorsion compensation using an image-guided system. Surgeons must be aware that a precise astigmatism axis marking is a fundamental step to obtain good astigmatism correction outcomes. In our practice, an accurate astigmatism axis marking was achieved in two steps: first, marking of the reference astigmatic axis with an image-guided system; second, marking of Purkinje reflex on the cornea with an inked tip of a Sinksey hook.