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Bao F, Lopes BT, Zheng X, Ji Y, Wang J, Elsheikh A. Corneal Biomechanics Losses Caused by Refractive Surgery. Curr Eye Res 2023; 48:137-143. [PMID: 36001080 DOI: 10.1080/02713683.2022.2103569] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Recent advances, specifically in the understanding of the biomechanical properties of the cornea and its response to diseases and surgical interventions, have significantly improved the safety and surgical outcomes of corneal refractive surgery, whose popularity and demand continue to grow worldwide. However, iatrogenic keratectasia resulting from the deterioration in corneal biomechanics caused by surgical interventions, although rare, remains a global concern. On one hand, in vivo biomechanical evaluation, enabled by clinical imaging systems such as the ORA and the Corvis ST, has significantly improved the risk profiling of patients for iatrogenic keratectasia. That is despite the fact the biomechanical metrics provided by these systems are considered indicators of the cornea's overall stiffness rather than its intrinsic material properties. On the other hand, new surgical modalities including SMILE were introduced to offer superior biomechanical performance to LASIK, but this superiority could not be proven clinically, creating more myths than answers. The literature also includes sound evidence that tPRK provided the highest preservation of corneal biomechanics when compared to both LASIK and SMILE. The aim of this review is twofold; to discuss the importance of corneal biomechanical evaluation prior to refractive surgery, and to assess the current understanding of cornea's biomechanical deterioration caused by mainstream corneal refractive surgeries. The review has led to an observation that new imaging techniques, parameters and evaluation systems may be needed to reflect the true advantages of specific refractive techniques and when these advantages are significant enough to offer better protection against post-surgery complications.
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Affiliation(s)
- FangJun Bao
- Eye Hospital, Wenzhou Medical University, Wenzhou, China.,The Institute of Ocular Biomechanics, Wenzhou Medical University, Wenzhou, China
| | - Bernardo T Lopes
- School of Engineering, University of Liverpool, Liverpool, UK.,Department of Ophthalmology, Federal University of Sao Paulo (UNIFESP), Sao Paulo, Brazil
| | - XiaoBo Zheng
- Eye Hospital, Wenzhou Medical University, Wenzhou, China.,The Institute of Ocular Biomechanics, Wenzhou Medical University, Wenzhou, China
| | - YuXin Ji
- Eye Hospital, Wenzhou Medical University, Wenzhou, China
| | - JunJie Wang
- Eye Hospital, Wenzhou Medical University, Wenzhou, China.,The Institute of Ocular Biomechanics, Wenzhou Medical University, Wenzhou, China
| | - Ahmed Elsheikh
- School of Engineering, University of Liverpool, Liverpool, UK.,Beijing Advanced Innovation Centre for Biomedical Engineering, Beihang University, Beijing, China.,National Institute for Health Research (NIHR) Biomedical Research Centre for Ophthalmology, Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
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Wilson A, Jones J, Marshall J. Biomechanical Evaluation of Decellularized and Crosslinked Corneal Implants Manufactured From Porcine Corneas as a Treatment Option for Advanced Keratoconus. Front Bioeng Biotechnol 2022; 10:862969. [PMID: 35497356 PMCID: PMC9046912 DOI: 10.3389/fbioe.2022.862969] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/14/2022] [Indexed: 01/13/2023] Open
Abstract
Currently corneal transplantation is the main treatment for late-stage keratoconus; however, transplantation procedures are accompanied by significant risk of post-surgical complications; this in addition to supply limitations imposed by a worldwide shortage of human donor corneas, has driven the development of alternative therapies. One such therapy is the use of corneal implants derived from porcine corneas (Xenia®, Gebauer Medizintechnik GmbH, Neuhausen, DE). In contrast to human donor tissue, these implants can be produced on demand and due to the processes used pose no risks for host-immune rejection. Their use has already been demonstrated clinically in patients for preventing the progression of topographic changes in keratoconus whilst improving visual acuity. The implants are derived from natural tissue and not standardised synthetic material, whilst this likely reduces the risk of issues with bio-incompatibility, there is inevitably variability in their intrinsic mechanical properties which requires investigation. Here, speckle interferometry is employed to examine the biomechanical properties, in response to physiologically representative forces, of native porcine corneal tissue prior to processing and after a proprietary 4-stage process involving decellularization, washing, compression and crosslinking. The control lenticules had an average Young’s modulus (E) of 11.11 MPa (range 8.39–13.41 MPa), following processing average E of the lenticules increased by 127% over that of the unprocessed tissue to 25.23 MPa (range 18.32–32.9 MPa). The variability in E of the lenticules increased significantly after processing suggesting variability in the propensity of the native tissue to processing. In summary, it is possible to produce thin (<90 µm) lenticules from porcine corneas with enhanced stiffness that are effective for treating late-stage keratoconus. Due to the observed variability in the responses of lenticules to processing, interferometry could be a useful technique for ensuring quality control in commercial production via biomechanical screening.
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Affiliation(s)
- Abby Wilson
- UCL Mechanical Engineering, London, United Kingdom
- Institute of Ophthalmology, UCL, London, United Kingdom
- *Correspondence: Abby Wilson,
| | - John Jones
- Laser Optical Engineering Ltd., Donington, United Kingdom
| | - John Marshall
- Institute of Ophthalmology, UCL, London, United Kingdom
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