High Astigmatism
Conditions
Keywords
SMILE PRO, High astigmatism, Small incision lenticule extraction, Astigmatic vector analysis, Cyclotorsion, Higher-order aberrations, Contrast sensitivity
Brief summary
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.
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.
Interventions
PROCEDURESMILE 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.
Sponsors
Hanoi Medical University
Study design
Allocation
NA
Intervention model
SINGLE_GROUP
Primary purpose
TREATMENT
Masking
NONE
Eligibility
Sex/Gender
ALL
Age
18 Years to 40 Years
Healthy volunteers
No
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
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Residual Refractive Astigmatism | 12 months postoperatively | Residual refractive astigmatism was measured using manifest refraction and analyzed with astigmatic vector analysis based on the Alpins method. |
| Refractive Accuracy (Spherical Equivalent Error) | 12 months postoperatively | Refractive accuracy was assessed using manifest refraction spherical equivalent (SEQ) after SMILE PRO surgery. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Refractive Stability Over Time (Spherical Equivalent) | 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively | Manifest refraction spherical equivalent (SEQ) was measured at each postoperative visit to evaluate refractive stability. |
| Refractive Cylinder Over Time | 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively | 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 (UDVA) | 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively | Uncorrected distance visual acuity was measured using standardized logMAR charts. |
| Corrected Distance Visual Acuity (CDVA) | 1 month, 3 months, 6 months, and 12 months postoperatively | Corrected distance visual acuity was assessed to evaluate visual safety after surgery. |
| Surgically Induced Astigmatism (SIA) | 3 months and 12 months postoperatively | 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 (TIA) | 3 months and 12 months postoperatively | 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) | 3 months and 12 months postoperatively | 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 (CI) | 3 months and 12 months postoperatively | 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 (AE) | 3 months and 12 months postoperatively | 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. |
| Higher-Order Aberrations | 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively. | Ocular higher-order aberrations were measured using wavefront aberrometry to assess postoperative visual quality. |
| Contrast Sensitivity | 1 week, 1 month, 3 months, 6 months, and 12 months postoperatively | Contrast sensitivity was evaluated under photopic conditions to assess functional visual quality. |
| Lenticule Decentration | Intraoperative | 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 | Intraoperative | 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. |
Countries
Vietnam
Contacts
PRINCIPAL_INVESTIGATORLan Tran, MD
Hanoi Medical University
Outcome results
None listed