Long-term Outcomes of SMILE PRO for High Astigmatism

Residual refractive astigmatism was measured using manifest refraction and analyzed with astigmatic vector analysis based on the Alpins method.

Refractive accuracy was assessed using manifest refraction spherical equivalent (SEQ) after SMILE PRO surgery.

Manifest refraction spherical equivalent (SEQ) was measured at each postoperative visit to evaluate refractive stability.

Manifest refractive cylinder was measured using subjective refraction and expressed in diopters (D) at scheduled postoperative visits following SMILE Pro surgery. This outcome evaluates the magnitude and stability of residual astigmatism during the 12-month follow-up period.

Uncorrected distance visual acuity was measured using standardized logMAR charts.

Corrected distance visual acuity was assessed to evaluate visual safety after surgery.

Surgically induced astigmatism, expressed in diopters (D), represents the vector magnitude of astigmatic change produced by surgery. It was calculated using the Alpins vector analysis method by comparing preoperative and postoperative refractive cylinder magnitude and axis.

Target induced astigmatism, expressed in diopters (D), represents the vector magnitude of astigmatic correction intended by the surgical plan. It was calculated using the Alpins vector analysis method based on the preoperative refractive cylinder magnitude and the planned axis of correction.

Difference vector (DV), expressed in diopters (D), represents the vector magnitude of residual astigmatism that would need to be corrected to achieve the intended target. It was calculated using the Alpins vector analysis method based on postoperative refractive cylinder magnitude and axis relative to the planned correction.

Correction index, expressed as a unitless ratio, represents the ratio of surgically induced astigmatism to target induced astigmatism. It was calculated using the Alpins vector analysis method to quantify the accuracy of astigmatic correction. A value of 1.0 indicates exact correction, values greater than 1.0 indicate overcorrection, and values less than 1.0 indicate undercorrection.

Angle of error, expressed in degrees (°), represents the angular difference between the achieved astigmatic correction and the intended target axis. It was calculated using the Alpins vector analysis method based on the deviation between the axis of surgically induced astigmatism and the planned treatment axis. Positive and negative values indicate counterclockwise and clockwise deviations from the intended axis, respectively.

Ocular higher-order aberrations were measured using wavefront aberrometry to assess postoperative visual quality.

Contrast sensitivity was evaluated under photopic conditions to assess functional visual quality.

Lenticule decentration is defined as the linear displacement between the intended lenticule center and the corneal vertex during SMILE PRO surgery. This parameter is automatically recorded intraoperatively by the CentraLign software integrated into the VisuMax 800 femtosecond laser system, based on real-time centration alignment guidance. Decentration is quantified as a continuous variable and expressed in millimeters (mm). For descriptive analysis, decentration values are categorized as < 0.1 mm, 0.1-0.19 mm, and ≥ 0.2 mm. For regression analyses, the continuous decentration value (mm) is used.

Intraoperative cyclotorsion is defined as the rotational misalignment (in degrees) between the preoperative reference axis obtained from iris registration and the intraoperative axis detected during docking using the OcuLign and CentraLign systems integrated into the VisuMax 800 platform. Cyclotorsion is recorded automatically by the system in degrees (°). Negative values indicate clockwise rotation and positive values indicate counterclockwise rotation. The magnitude of cyclotorsion is analyzed in relation to postoperative refractive outcomes.