Assessment of Corneal Biomechanical Properties Using Corvis ST Following LASIK, PRK, and CXL

To evaluate corneal biomechanical changes using the Corvis ST in patients who have under-gone LASIK, PRK, and corneal cross-linking (CXL).

Study Overview

• Status: Completed
• Conditions: Myopia; Keratoconus; Refractive Surgery
• Intervention / Treatment: Other: Corvis St Before and after lasik, PRK, CXL

Detailed Description

This observational study aims to evaluate corneal biomechanical changes in patients who have undergone LASIK, PRK, and corneal cross-linking (CXL) using the Corvis ST (Oculus). A total of 90 patients will be recruited from the ClearVision Laser Center database between January 2025 and December 2025. Participants will undergo non-contact biomechanical assessments at multiple postoperative time points to track corneal stability and elasticity over time.

Data Collection & Measurements Patient demographics, clinical history, and baseline preoperative data, including corneal thickness (pachymetry) and refractive status, will be collected. The Corvis ST will be used to measure key biomechanical parameters, such as Corneal Deformation Amplitude (CDA), Applanation Times (A1T & A2T), Radius of Curvature at Highest Concavity (RHC), Stiffness Parameter (SP-A1), Integrated Radius (IR), and the Corvis Biomechanical Index (CBI).

Measurement Protocol

All measurements will be conducted in a controlled environment with stable room temperature and humidity. Patients will be properly aligned, and three consecutive measurements per eye will be taken to ensure repeatability. Data will be recorded at specific intervals:

LASIK & PRK: 1 month, 3 months, 6 months, and 12 months CXL: 1 month, 3 months, 6 months, 12 months, and 24 months Potential Benefits & Risks The study aims to provide valuable insights into corneal biomechanical stability post-surgery, improving postoperative management and long-term visual outcomes. Risks are minimal, with only transient discomfort associated with the non-invasive Corvis ST measurements.

This study will contribute to a better understanding of corneal biomechanics in refractive and therapeutic procedures, potentially guiding future surgical decisions and patient care strategies.

• Study Type: Observational
• Enrollment (Actual): 150

Contacts and Locations

Study Locations

• Egypt
  • Giza Governorate
    • Mohandessin, Giza Governorate, Egypt, 11344
      • Clearvision

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult
• Accepts Healthy Volunteers: Yes

• Sampling Method: Probability Sample

Study Population

patients coming for refractive surgery

Description

Inclusion Criteria:

- 1. Adults aged 18-60 years. 2. Patients who have undergone LASIK, PRK, or CXL at least 1 month prior to measure-ment.

3. Stable refraction for at least 3 months post-procedure. 4. No evidence of active ocular disease or infection.

Exclusion Criteria:

• 1. History of other ocular surgeries (excluding LASIK, PRK, or CXL). 2. Presence of keratoconus or other corneal ectatic disorders not treated with CXL.

  3. Systemic or ocular conditions affecting corneal biomechanical properties (e.g., dia-betes, connective tissue disorders).

  4. Current or recent use of medications influencing corneal biomechanics.

Study Plan

How is the study designed?

Number of groups / cohorts

3

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Lasik; a non-contact air puff tonometer combined with Scheimpflug imaging to assess the cornea's deformation response. Measurements will be taken at multiple postoperative time points to track biomechanical changes. Key parameters such as Deformation Amplitude (DA), Stiffness Parameter (SP-A1), Applanation Times (A1 & A2), Peak Distance (PD), and Biomechanically Corrected IOP (bIOP) will be recorded.	Other: Corvis St Before and after lasik, PRK, CXL; corneal biomechanics measurment using corvis St
PRK; a non-contact air puff tonometer combined with Scheimpflug imaging to assess the cornea's deformation response. Measurements will be taken at multiple postoperative time points to track biomechanical changes. Key parameters such as Deformation Amplitude (DA), Stiffness Parameter (SP-A1), Applanation Times (A1 & A2), Peak Distance (PD), and Biomechanically Corrected IOP (bIOP) will be recorded.	Other: Corvis St Before and after lasik, PRK, CXL; corneal biomechanics measurment using corvis St
CXL; a non-contact air puff tonometer combined with Scheimpflug imaging to assess the cornea's deformation response. Measurements will be taken at multiple postoperative time points to track biomechanical changes. Key parameters such as Deformation Amplitude (DA), Stiffness Parameter (SP-A1), Applanation Times (A1 & A2), Peak Distance (PD), and Biomechanically Corrected IOP (bIOP) will be recorded.	Other: Corvis St Before and after lasik, PRK, CXL; corneal biomechanics measurment using corvis St

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
corneal biomechanics	6 month

Collaborators and Investigators

• Sponsor: Beni-Suef University

Publications and helpful links

General Publications

• Luce DA. Determining in vivo biomechanical properties of the cornea with an ocular response analyzer. J Cataract Refract Surg. 2005 Jan;31(1):156-62. doi: 10.1016/j.jcrs.2004.10.044.

Study record dates

Study Major Dates

• Study Start (Actual): September 1, 2023
• Primary Completion (Actual): May 28, 2025
• Study Completion (Actual): October 31, 2025

Study Registration Dates

• First Submitted: February 5, 2025
• First Submitted That Met QC Criteria: February 5, 2025
• First Posted (Actual): February 10, 2025

Study Record Updates

• Last Update Posted (Actual): November 19, 2025
• Last Update Submitted That Met QC Criteria: November 15, 2025
• Last Verified: June 1, 2025

More Information

Terms related to this study

• Keywords: lasik; corneal biomechanics; prk; cxl
• Additional Relevant MeSH Terms: Eye Diseases; Refractive Errors; Corneal Diseases; Myopia; Keratoconus
• Other Study ID Numbers: FMBSUREC/05012025/ Saif

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: UNDECIDED

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No
• product manufactured in and exported from the U.S.: No