Long-term Outcomes of SMILE PRO for High Astigmatism

Outcomes of SMILE PRO Surgery for the Correction of Myopia With High Astigmatism

This prospective interventional study aims to evaluate the long-term refractive and visual quality outcomes of SMILE PRO surgery in patients with myopia and high astigmatism. Eligible participants undergo small incision lenticule extraction using the VisuMax 800 femtosecond laser. Postoperative assessments include uncorrected and corrected distance visual acuity, manifest refraction, astigmatic vector analysis, contrast sensitivity, and higher-order aberrations. Participants are followed for up to 12 months to assess refractive accuracy, stability, safety, and visual quality after surgery.

Study Overview

• Status: Active, not recruiting
• Conditions: High Astigmatism
• Intervention / Treatment: Procedure: SMILE PRO surgery

Detailed Description

This is a single-center, prospective interventional clinical study conducted to assess the long-term refractive and visual quality outcomes of SMILE PRO surgery for the correction of myopia with high astigmatism. The study is performed at Hong Son Eye Hospital, Vietnam, following approval from the Institutional Review Board of Hanoi Medical University. All participants provide written informed consent prior to enrollment.

Patients aged 18 to 40 years with stable myopic refractive error and high astigmatism are eligible for inclusion. All eyes undergo small incision lenticule extraction using the VisuMax 800 femtosecond laser according to a standardized surgical protocol. Manifest refraction, corneal topography, and ocular imaging are performed by experienced refractive technicians using standardized measurement protocols. All patients are examined preoperatively and postoperatively by an ophthalmologist, who reviews clinical findings and surgical eligibility. All SMILE PRO procedures are performed by the same ophthalmic surgeon to minimize variability related to surgical technique.

Outcome measures include uncorrected and corrected distance visual acuity, spherical equivalent refraction, residual refractive astigmatism, and astigmatic vector analysis based on the Alpins method. Visual quality outcomes are further evaluated using contrast sensitivity testing and wavefront aberrometry to assess higher-order aberrations. Intraoperative parameters, including centration and cyclotorsion, are recorded and analyzed for their potential association with postoperative refractive outcomes.

Postoperative examinations are performed at 1 week, 1 month, 3 months, 6 months, and 12 months after surgery. The primary objective of this study is to evaluate the long-term refractive accuracy, stability, and safety of SMILE PRO surgery in eyes with high astigmatism. Secondary objectives include the assessment of preoperative and intraoperative factors influencing postoperative visual and refractive outcomes.

• Study Type: Interventional
• Enrollment (Estimated): 113
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Vietnam
  • Hanoi
    • Hanoi, Hanoi, Vietnam, 100000
      • Hong Son Eye Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: No

Description

Inclusion Criteria:

• Patients aged 18 to 40 years at the time of surgery
• Diagnosis of myopia with high astigmatism eligible for SMILE PRO surgery
• Stable refractive error prior to surgery
• Adequate corneal thickness and topographic parameters suitable for SMILE PRO
• Ability to understand the study procedures and provide written informed consent
• Willingness and ability to attend scheduled postoperative follow-up visits

Exclusion Criteria:

• Presence of corneal ectatic disorders or suspicious corneal topography
• History of previous ocular surgery or ocular trauma
• Active ocular disease other than refractive error
• Systemic diseases known to affect wound healing
• Pregnancy or breastfeeding at the time of surgery

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: N/A
• Interventional Model: Single Group Assignment
• Masking: None (Open Label)

Number of Arms

1

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: SMILE PRO surgery; Participants with myopia and high astigmatism undergoing small incision lenticule extraction using the SMILE PRO surgery.	Procedure: SMILE PRO surgery; Small incision lenticule extraction surgery performed using the VisuMax 800 femtosecond laser (SMILE PRO) for the correction of myopia with high astigmatism. The procedure is performed by a single experienced ophthalmic surgeon following a standardized surgical protocol.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Residual Refractive Astigmatism	Residual refractive astigmatism was measured using manifest refraction and analyzed with astigmatic vector analysis based on the Alpins method.	12 months postoperatively
Refractive Accuracy (Spherical Equivalent Error)	Refractive accuracy was assessed using manifest refraction spherical equivalent (SEQ) after SMILE PRO surgery.	12 months postoperatively

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Refractive Stability Over Time (Spherical Equivalent)	Manifest refraction spherical equivalent (SEQ) was measured at each postoperative visit to evaluate refractive stability.	1 week, 1 month, 3 months, 6 months, and 12 months postoperatively
Refractive Cylinder Over Time	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.	1 week, 1 month, 3 months, 6 months, and 12 months postoperatively
Uncorrected Distance Visual Acuity (UDVA)	Uncorrected distance visual acuity was measured using standardized logMAR charts.	1 week, 1 month, 3 months, 6 months, and 12 months postoperatively
Corrected Distance Visual Acuity (CDVA)	Corrected distance visual acuity was assessed to evaluate visual safety after surgery.	1 month, 3 months, 6 months, and 12 months postoperatively
Surgically Induced Astigmatism (SIA)	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.	3 months and 12 months postoperatively
Target Induced Astigmatism (TIA)	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.	3 months and 12 months postoperatively
Difference Vector (DV)	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.	3 months and 12 months postoperatively
Correction Index (CI)	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.	3 months and 12 months postoperatively
Angle of Error (AE)	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.	3 months and 12 months postoperatively
Higher-Order Aberrations	Ocular higher-order aberrations were measured using wavefront aberrometry to assess postoperative visual quality.	1 week, 1 month, 3 months, 6 months, and 12 months postoperatively.
Contrast Sensitivity	Contrast sensitivity was evaluated under photopic conditions to assess functional visual quality.	1 week, 1 month, 3 months, 6 months, and 12 months postoperatively
Lenticule Decentration	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
Intraoperative Cyclotorsion	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.	Intraoperative

Collaborators and Investigators

• Sponsor: Hanoi Medical University
• Investigators: Principal Investigator: Lan Tran, MD, Hanoi Medical University

Publications and helpful links

General Publications

• Pedersen IB, Ivarsen A, Hjortdal J. Changes in Astigmatism, Densitometry, and Aberrations After SMILE for Low to High Myopic Astigmatism: A 12-Month Prospective Study. J Refract Surg. 2017 Jan 1;33(1):11-17. doi: 10.3928/1081597X-20161006-04.
• Reinstein DZ, Archer TJ, Potter JG, Gupta R, Wiltfang R. Refractive and Visual Outcomes of SMILE for Compound Myopic Astigmatism With the VISUMAX 800. J Refract Surg. 2023 May;39(5):294-301. doi: 10.3928/1081597X-20230301-02. Epub 2023 May 1.
• Chan TCY, Wang Y, Ng ALK, Zhang J, Yu MCY, Jhanji V, Cheng GPM. Vector analysis of high (>/=3 diopters) astigmatism correction using small-incision lenticule extraction and laser in situ keratomileusis. J Cataract Refract Surg. 2018 Jul;44(7):802-810. doi: 10.1016/j.jcrs.2018.04.038. Epub 2018 Jun 13.
• Zhou J,Gu W,Gao Y,He G,Zhang F

Study record dates

Study Major Dates

• Study Start (Actual): December 10, 2024
• Primary Completion (Estimated): October 1, 2026
• Study Completion (Estimated): October 1, 2026

Study Registration Dates

• First Submitted: February 10, 2026
• First Submitted That Met QC Criteria: February 25, 2026
• First Posted (Actual): March 3, 2026

Study Record Updates

• Last Update Posted (Actual): March 3, 2026
• Last Update Submitted That Met QC Criteria: February 25, 2026
• Last Verified: February 1, 2026

More Information

Terms related to this study

• Keywords: Contrast sensitivity; Small incision lenticule extraction; SMILE PRO; High astigmatism; Astigmatic vector analysis; Cyclotorsion; Higher-order aberrations
• Other Study ID Numbers: #HMUIRB1649#

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: De-identified individual participant data underlying the results reported in this study will be made available. Shared data will include demographic characteristics, preoperative and postoperative refractive outcomes, visual acuity measurements, astigmatic vector parameters, contrast sensitivity results, and wavefront-derived higher-order aberrations. No personally identifiable information will be shared.
• IPD Sharing Time Frame: Data will be available beginning 12 months after publication of the primary results and will remain available for 5 years.
• IPD Sharing Access Criteria: Data will be shared with qualified researchers who submit a methodologically sound proposal. Requests will be reviewed by the study investigators, and data access will be granted after approval of the proposal and signing of a data use agreement.
• IPD Sharing Supporting Information Type: STUDY_PROTOCOL; SAP

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No