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To evaluate corneal biomechanical changes using the Corvis ST and ECD in patients who have under-gone LASIK, PRK, corneal cross-linking (CXL), Veriflex IOL and ICL.
This observational study aims to evaluate corneal biomechanical changes and ECD in patients who have undergone LASIK, PRK, corneal cross-linking (CXL), Veriflex IOL and ICL using the Corvis ST (Oculus) andEndocthelial cell Density . 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 Veriflex and ICL : 1 month, 3 months, 6 months, 12 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.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| 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. |
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| 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. |
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| 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. |
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| Veriflex and ICL | corneal Biomechanics and ECD measuments pre and postoperative . 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. |
| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Corvis St Before and after lasik, PRK, CXL, Veriflex IOL and ICL | Other | corneal biomechanics measurment using corvis St and corneal endothelial cell counts |
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| Measure | Description | Time Frame |
|---|---|---|
| corneal biomechanics | 6 month | |
| ECD measuments | corneal endothelial cell count measurments | Preoperative and 6 month postoperative |
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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.
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patients coming for refractive surgery
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Clearvision | Mohandessin | Giza Governorate | 11344 | Egypt |
| PubMed Identifier | Type | Citation | Retractions |
|---|---|---|---|
| 40866426 | Background | Saif PS, Okasha MG, Mahmoud H, Samir A, Abdelmonagy Ibrahim M. Impact of veriflex and ICL on corneal biomechanics and endothelial cell density. Sci Rep. 2025 Aug 27;15(1):31553. doi: 10.1038/s41598-025-14330-3. | |
| 41986537 | Background | Saif PS, Saif MYS, Abdel Dayem HMK, Elsayed MOA, Ibrahim MAM. Assessment of corneal biomechanical properties using Corvis ST following LASIK, PRK, and CXL. Lasers Med Sci. 2026 Apr 16;41(1):73. doi: 10.1007/s10103-026-04858-9. |
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| 15721708 | Background | 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. |
| ID | Term |
|---|---|
| D009216 | Myopia |
| D007640 | Keratoconus |
| ID | Term |
|---|---|
| D012030 | Refractive Errors |
| D005128 | Eye Diseases |
| D003316 | Corneal Diseases |
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